A review on the cultivation, bioactive compounds, health-promoting factors and clinical trials of medicinal mushrooms Taiwanofungus camphoratus, Inonotus obliquus and Tropicoporus linteus

Abstract

Medicinal mushrooms, such as Taiwanofungus camphoratus, Inonotus obliquus, and Tropicoporus linteus, have been used in traditional medicine for therapeutic purposes and promotion of overall health in China and many East Asian countries for centuries. Modern pharmacological studies have demonstrated the large amounts of bioactive constituents (such as polysaccharides, triterpenoids, and phenolic compounds) available in these medicinal mushrooms and their potential therapeutic properties. Due to the rising demand for the health-promoting medicinal mushrooms, various cultivation methods have been explored to combat over-harvesting of the fungi. Evidence of the robust pharmacological properties, including their anticancer, hypoglycemic, hypolipidemic, antioxidant, and antiviral activities, have been provided in various studies, where the health-benefiting properties of the medicinal fungi have been further proven through numerous clinical trials. In this review, the cultivation methods, available bioactive constituents, therapeutic properties, and potential uses of T. camphoratus, I. obliquus and T. linteus are explored.

Introduction

Natural products, consisting of an extensive range of structural and chemical diversity, have been used as therapeutic agents for various human ailments and diseases for many years [1]. Natural products and their derivatives have been approved for use in various fields, including oncology, as well as in the anti-infective area [2]. The biological activities of these natural sources can be attributed to the presence of medicinal compounds found in them, such as polysaccharides and terpenoids [3].

Medicinal mushrooms, including Taiwanofungus camphoratus, Inonotus obliquus, and Tropicoporus linteus, are rich sources of these bioactive constituents. Hispidin, ergosterol peroxide, protocatechuic acid, and betulin are all biologically-active compounds that can be found in the medicinal mushrooms. Having a long history of use in traditional and folk medicine, they have been used for the amelioration of conditions ranging from cancer [4] to heart and liver disease [5]. Modern scientific research has validated their claimed properties, where the increasingly developed field of medical mushroom research demonstrated the potent activities of bioactive compounds isolated from the fungi. They contain great potential to treat a wide range of conditions, including tumor [6, 7], diabetes [8,9,10], viral infections [11,12,13], and disease related to oxidative stress [14,15,16]. Evidence of their health-benefiting properties have been established through various studies and clinical trials [17]. Therefore, due to their significant pharmacological and health-promoting properties, various efforts have been made to increase their production sustainably [18].

The market value of medicinal mushrooms and their derived products was estimated to be USD 6.0 billion in 1999, with demand increasing between 20 and 40% annually since then [19]. With a selling price of up to US$25,000/kg, the annual output value of T. camphoratus in Taiwan is estimated to be about NT$3 billion [20] and a global market value of $100 million per year [21]. For I. obliquus, the current global market value of US$28.2 billion is expected to rise to US$87 billion by 2034 [22], while total sales of various T. linteus products in Japan and South Korea alone in 2023 have exceeded 10 billion yen (US$65 million) [23].

In view of the rising demand and expanding market potential, this review aims to explore the growth and cultivation, bioactive components, therapeutic potentials, medical evidence of the pharmacological properties of medicinal mushrooms Taiwanofungus camphoratus, Inonotus obliquus, and Tropicoporus linteus, with a goal of providing a useful reference for necessary information for the further study of the fungi.

Growth and cultivation

Taiwanofungus camphoratus

T. camphoratus thrives in the natural habitat of Taiwan's mountainous regions and grows at altitudes between 450 and 2000 m, where the Cinnamomum kanehirai tree serves as its primary nutrient source [24]. A distinguishing feature of T. camphoratus is its growth pattern, whereby the fruiting body can only develop to full maturity when the host tree has naturally aged away (Fig. 1).

Fig. 1

Fruiting bodies of (A) Taiwanofungus camphoratus, (B) Inonotus obliquus, and (C) Tropicoporus linteus on their host trees [25, 26] (Min and Kang 2021)

In the past, unsustainable methods have been practiced due to the high demand for wild T. camphoratus and the widespread use of C. kanehirai wood for furniture production. Fuelled by the need to satisfy this demand, excessive harvesting of the mushroom and its host tree has led to disastrous consequences on the availability of the fungi and its habitat [27]. Realizing the ecological importance of C. kanehirai and T. camphoratus’ reliance on this species, the Taiwanese government has intervened by setting conservation measures in place to prevent overexploitation and maintain the ecosystem’s ideal state [28]. However, due to its limited availability and difficult cultivation, T. camphoratus remains expensive and is often referred to as the “ruby in Taiwanese forests” [29].

Although between 80 and 85% of medicinal mushroom products are obtained from fruiting bodies, the continual rise in market demand has made mycelial products the wave of the future [30]. Artificial cultivation methods for T. camphoratus were established in order to reduce the effects of overexploitation and sustainably satisfy market demand. Two main cultivation techniques have been commonly utilized to meet the increasing demand, namely submerged fermentation and solid-state fermentation [31]. Each method possesses its own advantages and limitations, which have been described in Table 1. For example, the ability to precisely control physical, chemical, and biological factors using submerged fermentation allows high reproducibility of metabolites, thus increasing the ease of scale-up for industrial production purposes [32, 33]. Furthermore, recent efforts have been made to enhance the efficiencies of cultivation methods, such as the application of low-frequency alternating magnetic field to enhance mycelium growth, expression of genes involved in amino acid metabolism and synthesis, and accumulation of active metabolites in cultivated T. camphoratus [18].

Table 1 A comparison between two widely used techniques for the cultivation of medicinal mushrooms [34,35,36,37,38]

Inonotus obliquus

The Chaga mushroom, scientifically known as I. obliquus, is a parasitic fungus belonging to the family of Hymenochaetaceae that gained attention for its unique appearance and potential health benefits [39]. The development of I. obliquus can be recognized by a canker-like look in a shade of dark brown to black, resembling burnt wood, which is a result of fungal mycelium accumulation [40]. Despite its slow growth, I. obliquus ultimately reaches maturity, developing a distinctive texture and occasionally exposing its inner yellow flesh. The fungi frequently cohabit with birch trees in moist, wetland habitats through symbiotic interactions, whereby regions such as Russia, Korea, China, Eastern and Northern Europe, northern parts of the United States, and portions of Canada are included in their geographic distribution [41].

I. obliquus must be harvested using special procedures to protect the wellbeing of both the host tree and the fungi. It can be carefully removed from a tree's bark using equipments such as hatchets or hammers without harming the inner layers [42]. The optimal time to harvest I. obliquus is in late winter when the host tree is dormant and nutrient accumulation is at its greatest. This method allows for repeated regeneration of I. obliquus on the same tree while protecting the health of the host tree. A complex relationship exists between I. obliquus and its host tree, whereby the viability of the fungi declines with the health of the tree [42]. Thus, it is essential to understand the symbiotic relationship between I. obliquus and its host to enable appropriate cultivation methods for this priceless natural resource.

Due to the slow-growing nature and hence limited supply of I. obliquus, various cultivation methods have been employed to address this issue. A 2005 study on the optimum culture condition of I. obliquus provided valuable basic information on the in vitro cultivation conditions, including the media used and additions such as amino acids and yeast extract for the improvement of fungal growth and biomass production [43]. Submerged fermentation has been commonly used for the production of I. obliquus, whereby careful optimisation of optimum broth formula for submerged culturing of I. obliquus mycelium has successfully enhanced mycelial biomass yields [44]. Other efforts have also been made to determine the optimum I. obliquus strains and cultivation substrates for producing productive strains of the medicinal fungi, where the use of Betula wood as inoculation dowels was suggested to shorten production time [45].

Tropicoporus linteus

T. linteus is a well-known medicinal fungus that has drawn the interest of researchers and traditional medicine practitioners. It is known by several names, including "sanghuang" in China, "meshimakobu" in Japan, and "sangwhang" in Korea. Due to limited availability in the wild, its development and harvest present added challenges.

T. linteus is usually found on the trunks Populus Linn., Quercus Linn., Toxicodendron vernicifluum and Morus alba Linn. in its natural habitat [46]. It stands out in the fungi world due to its unusual pileate, perennial, horseshoe-shaped basidiocarps [46]. When dried, the pore surface changes from rusty brown to brown, the pial surface from a dark brown hue to black, and the tubes attain a cinnamon-yellowish-brown tint. The months of April and May are when T. linteus is most suitable for harvesting in the wild due to favourable environmental circumstances for its growth [47].

Despite its significant therapeutic value, the availability of T. linteus for traditional medicine and industrial use has been constrained by its low abundance in its natural environment, where the demand for this rare resource simply exceeds what the wild population can supply [48]. Researchers and cultivators have concentrated on artificially producing T. linteus to address this issue, where cultivation procedures to produce fruiting bodies often require growing it on solid artificial substrate [49]. Optimal submerged culture composition and conditions for maximum mycelial biomass have also been determined, enabling a more sustainable and steady supply for medical and scientific uses, and utilization of this unique fungus to its maximum potential [50]. Furthermore, artificial cultivation of T. linteus strains on oak logs has been successful, with resulting polysaccharides retaining their valuable bioactive properties, including immunomodulatory and anticancer effects [51].

Bioactive compounds

The chemical structures of bioactive compounds isolated from the three medicinal mushrooms explored in this review are presented in (Fig. 2).

Taiwanofungus camphoratus

Polysaccharides

A water-soluble polysaccharide, composed of β-D-glucan, was isolated and purified from cultured Taiwanofungus camphoratus powder [52]. The polysaccharide was found to have a molecular weight of 17.2 kDa, where further structural elucidation revealed a segmental and repetitive structure of the molecule, composed of 1,3,6-β-d-glucose, 1,3-β-d-glucose, and 1,4-α-d-galactose at a 2.21:1.00 mol ratio of glucose to galactose. The β-d-glucan was demonstrated to exert anti-inflammatory and anti-oxidation activities in lipopolysaccharide (LPS) induced-human hepatocytes to thus provide a hepatoprotective effect. An exopolysaccharide [53] and galactoglucan primarily composed of galactose (1,6-β-d-galactose) and glucose (1,6-β-d-glucose, 1,3-α-d-glucose, and 1,4-β-d-glucose), with terminal α-d-6-deoxyglucose and α-d-glucose [54] isolated from T. camphoratus also exhibited inflammation-reducing capabilities.

Fig. 2

Chemical structures of bioactive compounds isolated from Taiwanofungus camphoratus (1–38 terpenes and terpenoids; 39–42 quinone derivatives; 43–47 maleic and succinic acid derivatives), Inonotus obliquus (38, 48–88 terpenes and terpenoids; 89–113 phenolic compounds), and Tropicoporus linteus (114–132 terpenes and terpenoids; 93, 95, 97, 99, 111, 112, 133–142 phenolic compounds)

Three other polysaccharides from the cell wall of T. camphoratus mycelia obtained through hot water, cold alkali, and hot alkali extraction were demonstrated to also mainly consist of glucose, with molar percentages of 75.32, 78.06, and 87.28 respectively [55]. The hot water extracted polysaccharide mainly consisted of 1,4-d-glucose, while those isolated through cold and hot alkali extractions were primarily composed of 1,3-d-glucose and were reported to contain potent in vitro antioxidant properties, suggesting the potential contribution of 1,3-d-glucose towards the observed activities exerted by the alkali-soluble polysaccharides. Another polysaccharide extracted from the mycelia of T. camphoratus was shown to possess antitumor activities [56]. Contrary to the polysaccharides isolated by previous researchers [52, 53, 55], this polysaccharide only contained trace amounts of glucose, as it is mainly composed of mannose, xylose, arabinose, fucose, and rhamnose in a ratio of 31.27:1.77:1.44:1.34:1.00, with a backbone composed of repeating α-1,3-, α-1,6-, α-1,2-, and α-1,4-glycosidic linkages.

Recently, sulfated polysaccharides obtained from T. camphoratus grown in zinc sulfate enriched culture conditions were studied by Lee et al. [57]. It was found that the sulfated polysaccharides not only contain inflammation-inhibiting properties but also possess anti-lung cancer activities. In a comparison of sulfated polysaccharides to non-sulfated groups, sulfated derivatives showed more robust anti-inflammatory effects than non-sulfated polysaccharides, thus suggesting the role of sulfation in the inflammation-reducing capacities of the bioactive compound [58]. In another study, a 13.5 kDa heterogalactan was extracted from T. camphoratus and found to be composed of α-d-1,6-linked galactose backbone chain with terminal α-d-mannose and α-l-fucose every six galactose residues [59]. Similar to the results observed by Chen et al. [58], the mannofucogalactan itself did not demonstrate inhibitory effects on angiogenesis, while its sulfated derivative exerted a significant dose-dependent reduction of tube formation.

Besides sulfated derivatives, selenium-enriched polysaccharides have also been analyzed [39]. It was reported that in vitro scavenging efficiency was greatly enhanced following selenium enrichment, thus making selenium-enriched T. camphoratus polysaccharides a promising antioxidant agent for food and pharmaceutical applications.

It is noteworthy to mention that besides from the variety of bioactive components, alkali-extracted dietary fiber from the residues of T. camphoratus basswood cultured fruiting body also serves as a promising source of functional ingredients [60]. The study highlighted that the dietary fiber promoted RAW 264.7 cell proliferation, phagocytosis, nitric oxide (NO) production, and release of pro-inflammatory cytokines tumour necrosis factor alpha (TNF-α) and interleukin-1 beta (IL-1β), thus revealing its immunomodulatory properties, and possibly other bioactivities.

Terpenes and terpenoids

Evaluation of new ergostane-type triterpenoids, antcamphorols A-K, (1–11) revealed ROS scavenging abilities of antcamphorols G (7), I (9), and J (10), along with cytotoxic activities of antcamphorols C and H against U251 and MCF-7 [61]. Furthermore, through isolation from dish cultures of T. camphoratus, three new (12–14) and 10 known isolated triterpenoids (15–24) were demonstrated to possess cytotoxic activities on cancer cell lines HL60, U251, SW480, and MCF-7 [62]. Interestingly, it was found that the combination of two of the isolated triterpenoids (25, 26) could enhance the cytotoxic effect of paclitaxel, an established anti-cancer agent, suggesting triterpenoids as potential sensitizers of paclitaxel for chemotherapy. Antcamphin Z (27) also displayed potent cytotoxic activities against human cancer cells (U251, HL60, SW480, and A549) with no significant effects on normal cells (LO2) [63]. Besides their cytotoxic activities, triterpenoids antcins A (28) [64], B (29), H (30), and K (31) [65] have also been reported to exert an anti-inflammatory effect.

Using chiral-supercritical fluid chromatography (SFC), R/S epimeric pairs of ergostane triterpenoids, including antcin A (28) and antcin B (29), were separated from T. camphoratus at a higher efficiency than high-performance liquid chromatography (HPLC) [66]. This thus demonstrates chiral-SFC as a more advantageous method for separation of epimeric bioactive compounds. Mechanochemical-assisted extraction has also been used for the isolation of triterpenoids from the medicinal fungus, where extracts containing triterpenoids (32, 33) obtained through this technique led to more robust antioxidant, anti-inflammatory, and immunomodulatory activities than ethanol thermal reflux-extracted compounds [67].

Steroids (34–37) isolated from the medicinal mushroom have exhibited cytotoxic activities against murine colorectal and human leukemia cancer cell lines [68]. Furthermore, ergosterol (38) obtained from T. camphoratus was recently found to significantly reduce nuclear factor kappa B (NF-κB) phosphorylation, microglial activation–associated ionized calcium-binding adapter molecule-1 (IBA-1), and LPS-induced neuron damage, therefore making it an effective anti-neuroinflammatory agent [69].

Quinone derivatives

A novel quinone derivative, coenzyme Q0 (CoQ0, 2,3-dimethoxy-5-methyl-1,4-benzoquinone) (39), was isolated from fermented culture broth of T. camphoratus by Yang et al. [70]. This new compound was found to be capable of inducing apoptosis and autophagic cell death both in vitro in human glioblastoma cells and in vivo in glioblastoma-xenografted mice, through increased reactive oxygen species (ROS) production.

Another bioactive constituent found in the mycelium of T. camphoratus is antroquinonol (40), which is a ubiquinone derivative. Antroquinonol has been reported to inhibit the migration and invasion of breast cancer cells, through suppression of matrix metalloproteinase-9 (MMP-9) and epithelial-mesenchymal transition (EMT) gene expressions [71], while antroquinonol Y (41) also exerts significant cytotoxic effects on human cancer cells (U251, HL60, SW480, and A549) without affecting normal cells (LO2) [63]. Furthermore, bioassay-guided isolation from methanolic extracts of T. camphoratus revealed a potent anti-inflammatory compound, 4-acetylantroquinonol B (42), which significantly inhibited polyinosinic-polycytidylic acid-induced NO production by RAW264.7 macrophages [72]. Hence, due to the highly potent anti-tumor properties and demonstrated bioactivities of antroquinonol, many studies have been conducted to enhance its synthesis [73,74,75,76,77,78].

Maleic and succinic acid derivatives

Antrodins (43–47) are maleimide derivatives found in T. camphoratus mycelium and have been found to inhibit Hepatitis C virus (HCV) protease [79]. Antrodin A (43) has been reported to possess hepatoprotective properties and alleviate intestinal flora dysbiosis [80], while antrodin B (44) contains anti-hepatofibrotic activity [81]. Antrodin C (45) has been found to reduce the pathology of Alzheimer’s disease [82], protect against liver fibrosis [83], and exert cytotoxic activities against colorectal cancer cells [84].

Inonotus obliquus

Polysaccharides

Polysaccharides components of Inonotus obliquus have been studied by many researchers for their variety of biological activities. Two polysaccharides (HIOP1-S and HIOP2-S) were obtained from I. obliquus, where HIOP1-S was primarily composed of glucose (29.673%) and galactose (20.547%) and HIOP2-S mainly consisted of glucose (49.881%) [85]. Interestingly, HIOP1-S consisted of both α-and β-glycosidic bonds, while HIOP2-S only contained β-type linkages. Despite the considerable divergences between the two polysaccharides, both were capable of inhibiting α-glucosidase activity and enhancing extracellular glucose consumption in insulin-resistant cells. Another study also isolated two polysaccharides from the medicinal mushroom, IOEP1 and IOEP2, that contained both α-and β-glycosidic bonds [86]. The pyran-type polysaccharides were reported to mainly consist of galactose and mannose (IOEP1) and arabinose (IOEP2), and were both also demonstrated to increase glucose consumption of insulin-resistant cells, thus exerting a hypoglycemic effect.

A polysaccharide, composed of galactose, glucose, xylose, and mannose (2.0:3.5:1.0:1.5 molar ratio), was extracted from I. obliquus and found to exert free-radical scavenging activities, antioxidant effects, and enhancement of nitric oxide release [87]. A polysaccharide extracted by Hu et al. [88] also exhibited antioxidant properties, and consisted of mannose, rhamnose, glucose, galactose, xylose, and arabinose in a molar ratio of 9.81:3.6:29.1:20.5:21.6:5.4. The antioxidative properties of another I. obliquus polysaccharide with a molecular weight of 111.9 kDa, through the regulation of the nuclear factor erythroid 2-related factor 2 (Nrf2) pathway, were found to contribute a protective effect against Alzheimer’s disease [89].

Neutral (60–73 kDa), acidic (10–31 kDa) and alkaline (> 450 kDa) polysaccharide fractions isolated from I. obliquus extracts, consisting primarily of 1,3- and 1,6-linked-β-glucose, were reported to possess immune-promoting activities [90]. Chen et al. [91] successfully obtained a novel polysaccharide from I. obliquus (IP3a). It was found that IP3a is composed of arabinose, galactose, rhamnose, and glucose (4.6:2.6:2.5:1.0), and possesses pro-apoptotic and immune-enhancing effects. A pro-apoptotic effect was also observed in a polysaccharide containing mainly glucose (74.95%), where it was found that the apoptosis-inducing effects were mediated by activation of adenosine monophosphate-activated protein kinase (AMPK) and reduction of mitochondrial membrane potential (MMP) [92].

Recently, another polysaccharide was isolated and found to have a molecular weight of 373 kDa, with a composition of 9 monosaccharides, primarily contributed by glucose (29.85%), galactose (20.70%), and mannose (14.19%) [93]. The polysaccharide was found to be capable of increasing Firmicutes, decreasing Bacteroidetes, and repairing the intestinal barrier to contribute to the protection against Type 2 diabetes mellitus. Interestingly, contrary to the findings of Su et al. [93], a polysaccharide consisting of mannose, galactose, and glucose (7.7:23.3:32.6) reduced the abundance of Firmicutes and enhanced Bacteroidetes [94], thus suggesting the impact of polysaccharide composition on biological activities.

Terpenes and terpenoids

Inotodiol (48) and trametenolic acid (49) are common triterpenoids found in I. obliquus, and were found to exert anti-proliferative activities on AGS, MCF-7, and PC3 cancer cells [95], and alleviate liver diseases through modification of the farnesoid X receptor (FXR)/small heterodimer partner (SHP)/ sterol-regulatory element binding protein-1C (SREBP-1C) axis [96]. Besides that, betulin (50) and betulinic acid (51) also inhibited the proliferation of human adenocarcinoma and human lung carcinoma cell lines, while inotodiol (48), 3β-hydroxy-8,24-dien-21-al (52), and betulin-3-O-caffeate (53) possessed immunomodulatory capabilities [97]. In addition, Zou et al. [98] highlighted the neuroprotective effects of triterpenoids lanosterol (54), inotodiol (48), and inonotsutriol A (55), while Park et al. [99] demonstrated the NO-inhibiting effects of inotodiol (48), inonotsutriol A (55), and trametenolic acid (49).

Another bioactive compound, known as ergosterol peroxide (56), was found to exert anti-cancer properties against colorectal cancer [100], prostatic carcinoma and breast carcinoma cells [101]. Ergosterol peroxide (56), ergosterol (38), and trametenolic acid (49) have also been demonstrated to have anti-inflammatory capabilities [101]. Moreover, a wide variety of I. obliquus-obtained triterpenoids (57–66) were observed to have inhibitory effects on α-glucosidase [102].

Besides known compounds, new triterpenes and triterpenoids have been elucidated and found to also contain biological activities. Two new triterpenes, inonotusane D (67) and inonotusol G (68), isolated by Zhao et al. [103] and Liu et al. [104] respectively, exhibited cytotoxic effects against cancer cells. Besides that, another new lanostane-type triterpene, inonotusane C (69), also exhibited cytotoxic activities against A549 and HeLa cell lines [105] thus demonstrating their chemotherapeutic potentials.

A total of 12 previously uncharacterized lanostane triterpenoids (70–81) were isolated by Zou et al. [98, 106], where it was revealed that compound 77 is capable of exerting neuroprotective activities. Another study also obtained novel lanostane-type triterpenoids, inonotusols H-N (82–88), that were found to significantly inhibit NO release by microglial cells, where inonotusols I (83) and L (86) were capable of interacting with inducible-nitric oxide synthase (iNOS) protein to hence exert a neuroprotective effect [107].

Phenolic compounds

Phenolic compounds, including phenolic acids and flavonoids, are produced by the sclerotia of I. obliquus and have been found to possess potent bioactivities. A phenolic compound isolated from I. obliquus, identified as inoscavin A (89), was demonstrated to improve cell viabilities of H₂O₂)-injured human neuroblastoma cells to exert a neuroprotective effect through their antioxidant activities [108]. Phenolic (91–97) and polyphenol compounds (98–107), isolated by Hwang et al. [109] and Wang et al. [110] respectively were reported to contain radical scavenging activities in a dose-dependent pattern.

Melanins are another type of phenolic compound found in I. obliquus and have been associated with immunomodulatory properties. A water-soluble melanin fraction was found to be capable of inhibiting the complement cascade and suppressing NO production by murine macrophages [97]. Melanins isolated from aqueous extracts of I. obliquus also exhibited antioxidant activities, thus creating an optimum growth condition for obligate anaerobe Bifidobacterium bifidum [111].

A recent study revealed that ultraviolet (UV) radiation led to an increased accumulation of both extracellular and intracellular polyphenols and flavonoids, which led to the UV-irradiated extracts’ enhanced capabilities to scavenge free radicals [112]. Another study was also able to increase exo- and endo-polyphenols production through application of stimulatory agents, where only 1.0 g/L of the most effective agent, linoleic acid, was found to significantly improve the synthesis of ferulic acid (108), gallic acid (104), epicatechin-3-gallate (ECG) (109), epigallocatechin-3-gallate (EGCG) (110), phelligridin G (111), inoscavin B (90), and davallialactone (112) to give rise to more robust scavenging activities of the treated extracts [113]. Tween-20 was also proven to be a potent stimulatory agent for the increase in polyphenols ferulic acid (108), naringin (113), ECG (109), EGCG (110) content, which subsequently led to enhanced antioxidant activities of treated products [114].

Tropicoporus linteus

Polysaccharides

A water-soluble heteropolysaccharide was isolated from the mycelia of Tropicoporus linteus, with a composition of arabinose, xylose, glucose, and galactose in the molar ratio of 4.0:6.7:1.3:1.0 and a molecular weight of 343,000 kDa, whereby the backbone consisted of α-1,2-, α-1,4, β-1,4-, and β-1,5-glycosydic bonds [115]. The polysaccharide was capable of regulating the mitogen-activated protein kinases (MAPK) and peroxisome proliferator-activated receptor (PPAR) signalling pathways to exert an anti-inflammatory effect. Another high molecular weight polysaccharide (123.8 kDa) that is rich in galacturonic acid (35.7% of monosaccharide composition) with small amounts of arabinose, galactose, xylose, rhamnose, and fucose showed immunostimulatory activities [116].

A lower molecular weight (1,3;1,6)-β-D-polysaccharide (20.7 kDa) consisting mainly of glucose (78.88%) mannose (8.32%) and galactose (8.06%) was also obtained from T. linteus [117]. It was reported to inhibit TNF-α and IL-6 release in RAW264.7 cells, while increasing IL-10 levels, thus suggesting a possible role in the restoration of the IL6/IL10 balance. Another polysaccharide with a molecular weight of 15.5 kDa is also mainly made up of glucose (53.2%), mannose (14.9%), and galactose (13.5%) with 5.5% composition of (1,3;1,6)-β-d-glucans, where it was found to be capable of inhibiting NO production in RAW264.7 cells [118].

Three antioxidant polysaccharides, PL-W, PL-A, and PL-N, were extracted from the mycelia of T. linteus, where PL-W was composed of glucose and mannose (molar ratio 8:1), PL-A composed of glucose, mannose, xylose, and arabinose (molar ratio 8:1:1:1), while PL-N consists of xylose, arabinose, glucose, and galactose (7.8:5.5:1.8:1.0) [119]. All three polysaccharides were soluble in water at 10 g/L and possess potent antioxidant capacities in a concentration-dependent manner. This is in agreement with the findings of Yan et al. [120], where PL-N was found to have antioxidant activities, which can be enhanced by ultrasonic treatment. Besides that, two novel heteropolysaccharides, PLP1-I and PL-A11, with molecular weights of ∼290,000 kDa and 13.8 kDa respectively, were obtained from T. linteus mycelia [121, 122]. PLP1-I consists of only glucose and galactose (molar ratio 8.9:1.0) with a 1,4-α-d-glucopyranose backbone, while PL-A11 is composed of arabinose, xylose, mannose, and glucose (molar ratio 1.1:1.3:1.0:6.6) with a 1,4-α-d-glucopyranosyl, 1,2-α-d-xylopyranosyl, and 1,3-α-d-arabinofuranosyl backbone. Nevertheless, both polysaccharides were found to increase antioxidant enzyme activities in a dose-dependent manner. Another two polysaccharides with antioxidative activities, PLPS and C-PLPS, was recently isolated, where both contained arabinose, xylose, mannose, glucose, and galactose in molar ratios of 1.0:1.8:3.8:40.1:1.4 and 1.0:1.5:3.4:25.2:1.1 respectively [123].

A branched-type glycan with an average molecular weight of 3172.9 kDa, pyranoid sugar ring conformation, and α- and β-linkages was found to be capable of exerting an anti-diabetic effect by reducing blood glucose levels in diabetic mice [124]. This agrees with the findings of Liu et al. [125] where two T. linteus polysaccharides with backbones consisting of repeating α-d-glucose(1,4)-α-d-glucose(1,6) units (PLPS-1) and 1,3-α-d-glucose and 1,6-α-d-glucose (PLPS-2) respectively were observed to ameliorate insulin resistance.

A thorough evaluation of PLPS-1 and PLPS-2 previously conducted by Mei et al. [126] revealed that PLPS-1 consisted of glucose, arabinose, fucose, xylose in a molar ratio of 21.964:1.336:1.182:1:1, while PLPS-2 consisted of glucose, galactose, mannose, arabinose, fucose, xylose in a molar ratio of 14.368:2.594:1.956:1.552:1.466:1, where PLPS-1 was found to possess antitumor activities against S180 sarcoma cells. Another 343,000 kDa polysaccharide was reported to exert antitumor activities against HepG2 cells [127] and a hepatoprotective effect in mice [128], where structural characterization revealed the presence of seven glycosidic residues Araf (1 → , → 5) Araf (1 → , → 4) Xylp (1 → , → 2) Xylp (1 → , → 2,4) Xylp (1 → , → 4) Glcp (1 → , and → 4,6) Galp (1 → in the molar ratio of 2.28:1.83:3.17:2.64:1.03:1.36:1.00.

A polysaccharide composed of glucose, galactose, mannose, fucose, and xylose in a molar ratio of 4.36: 2.34: 2.09: 0.88: 0.42 showed prebiotic potentials by increasing amounts of beneficial bacteria, such as Bacteroides, Prevotella, and Butyricimonas, and reducing pathogenic bacteria including Escherichia, Shigella, Morganella, and Intestinimonas [129]. Besides that, a polysaccharide with a monosaccharide composition of fucose, rhamnose, arabinose, glucuronic acid, galactose, glucose, and xylose (1.4:0.5:0.9:1.6:4.7:84.8:6.0) exerted bacterio-static activities against bacteria Staphylococcus aureus, Escherichia coli, and Bacillus subtilis, demonstrating the potential of T. linteus polysaccharides for clinical applications [130].

Terpenes and terpenoids

Phellilane L (114) is a cyclopropane-containing sesquiterpenoid isolated from T. linteus that was found to possess antimicrobial activities against P. gingivalis [131]. A γ-Ionylidene-type sesquiterpenoid obtained from T. linteus, (-)-trans-γ-monocyclofarnesol (115), also exhibited antimicrobial effects on P. gingivalis [132], while phellidene E (116), ( +)-γ-ionylideneacetic acid (117) [132] and phellilane H (118) [133] did not show any detectable activities. Besides that, phellinulins A-N (119–132) were extracted from the mycelium of T. linteus, where phellinulins A (119), H (126), I (127), K (129), and M (131) were found to have hepatoprotective properties [134].

Phenolic compounds

Phellifuropyranone A (133) and phelligridin G (111) can be found in T. linteus, and possess in vitro antiproliferative activity against mouse melanoma and human lung cancer cells [135]. Several other polyphenols, including hispidin (134), phelligridimer A (135), davallialactone (112), methyldavallialactone (136), hypholomine B (137), interfungin A (138), inoscavin A (139), protocatechuic acid (97), protocatechualdehyde (95), caffeic acid (99), and ellagic acid (140) were also isolated by Lee et al. [136], where davallialactone (112), hypholomine B (137), and ellagic acid (140) were capable of inhibiting aldose reductase to reduce diabetic complications. In addition, davallialactone (112), hispidin (134), hypholomine B (137), and caffeic acid (99) were found to have antioxidant activities [137], while hispidin (134) and hypholomine B (137) also exerts hypolipidemic and hepatoprotective effects [138].

In agreement with Min et al. [137] and Chiu et al. [138], hispidin (134) have been demonstrated to be a potent antioxidant by various studies, thus providing protection against oxidative stress [139,140,141,142]. Due to the significant bioactivities and potential applications of hispidin, methods have been developed to enhance the production of hispidin, such as through solid-state fermentation using pearl barley medium [143].

Another notable polyphenol that has been detected in T. linteus is hispolon (141) [144]. Hispolon has been reported to have various pharmacological activities, such as anti-inflammatory properties, [145,146,147,148], antioxidant activities [149], and antitumor effects [150,151,152,153].

A catechol-containing phenylpropanoid derivative found in T. linteus, 3,4-dihydroxybenzalacetone (Osmundacetone) (93), has been shown to attenuate inflammation [154], exert antioxidant activities [155], suppress the metastasis and formation of cancer [156], and protect against aging-associated myocardial alterations [157]. Osmundacetone (93) and inotilone (142), have also been isolated from T. linteus, where they have been demonstrated to have antioxidant properties [158] and inhibit neuraminidase activity to thus exert an antiviral effect [13].

Health-promoting properties

Taiwanofungus camphoratus

Anticancer

T. camphoratus possesses a wide range of health-benefiting properties, which has been summarized in Table 2, whereby its anticancer properties are probably the most extensively studied aspect (Fig. 3). The ethanolic extract of T. camphoratus have been shown to exert anticancer effects on SMMC-7721 and HepG2 cells through inhibiting the activation of signal transducer and activator of transcription 3 (STAT3) [159], and B16-F0 cells via inducing cell cycle arrest and apoptosis [160]. Additionally, T. camphoratus ethanolic extracts also induced cell cycle arrest and suppressed the growth of Hep 3B and Hep J5 cells, where caspase-3 and cell cycle inhibitors p21 and p27 were also activated in the cells [161]. Three ergostane-type triterpenes isolated from the fruiting bodies of T. camphoratus caused a significant increase of HT-29 (Colon cancer) cells in the sub-G1 phase from the control value of 0.77% to about 41%, 32% and 29% respectively (Compound 1, 2 and 3), strongly indicating the ability of these triterpenes to induce apoptosis in HT-29 cells [162].

Table 2 Health-promoting properties of Taiwanofungus camphoratus extracts and bioactive compounds

Furthermore, triple-negative breast cancer (MDA-MB-231) cells were also responsive to the anticancer effects of the fermented culture of T. camphoratus, through an inhibition of the EMT, further suggesting the potential of T. camphoratus as an anticancer agent [163]. Moreover, Yang et al. [164] reported that the fermented culture of T. camphoratus also produced inhibitory effects against SKOV-3 human ovarian carcinoma cells via suppression of the HER-2/neu signalling pathway. Besides, the fermented culture of this mushroom extract also exerted a dose- and time-dependent series of apoptotic events in MCF-7 cells, as evidenced by the accumulation of cells in the sub-G1 phase, chromatin condensation, internucleosomal DNA fragmentation, and loss of cell viability [165].

Fig. 3

Mechanisms found to be employed by Taiwanofungus camphoratus to exert anticancer effects

The crude extract of the fruiting body of cultivated T. camphoratus induced cytotoxicity on HeLa and C-33A human cervical cancer cell lines, with higher potency recorded on C-33A in comparison to HeLa cells [166]. According to the results of the caspase activity assay, the crude extract significantly increased the activities of caspase-3, -8, and -9 in HeLa and C-33A cells and led to a dose-dependent rise in cytosolic cytochrome in the cytochrome c assay, thus indicating that apoptosis involves both intrinsic and extrinsic signalling pathways [166]. Similar effects were also exerted by the crude extract on SKOV-3 and TOV-21G ovarian cancer cells where the activity of caspases-3, -8, -9 and cytochrome c were found to be increased [167]. Bad protein from the Bcl-2 family was observed to be increased in SKOV-3 cells while the expression of Bim and Bak proteins increased and Bcl-xL decreased in TOV-21G cells. Moreover, T24 bladder cancer cells were also found to be susceptible to the crude extract of T. camphoratus with a concentration of about 50 µg/mL with about half of the cells in the control being inhibited at the 72 h time-point [168].

The ethyl acetate extract of T. camphoratus was reported to be effective in the liver cancer cell line Hep 3B via the increase of cytoplasmic calcium (Ca²⁺) and subsequent induction of calpain and caspase-12 activation [169], as well as HepG2 and PLC/PRF/5 cells, as evidenced by the marked increase in apoptotic promoting factors [170]. In addition, Hep3B and HepG2 cells were also susceptible to the methanolic extract of T. camphoratus, where treatment for 72 h resulted in apoptosis of around 40% of the Hep3B cells and 98% of the HepG2 [171]. Furthermore, Rao et al. [172] reported that methanol extract also inhibited Jurkat leukaemia cells with IC₅₀ value of approximately 40 µg/mL.

The solid-state cultured broth of T. camphoratus also managed to exert synergistic antiproliferative effects in C3A and PLC/PRF/5 hepatoma cells when administered in combination with cisplatin and mitomycin via the inhibition of the multidrug resistance (MDR) gene expression and the cyclooxygenase-2 (COX-2)-dependent inhibition of phospho-protein kinase B (p-Akt), which in turn resulted hepatoma cells to undergo apoptosis [173].

Hypoglycemic and hypolipidemic

T. camphoratus is also known for its antiglycemic effects, where antcin K from the fruiting body of T. camphoratus can enhance membrane glucose transporter 4 (GLUT4) and p-Akt expressions in vitro in C2C12 myotube cells and induce an antihyperglycemic effect (40 mg/kg/day) comparable to Metformin (300 mg/kg/day) in vivo in C57BL/6J mice [174]. Another compound, eburicoic acid TRR, from T. camphoratus was able to increase AMPK phosphorylation, Akt, and membrane GLUT4 level in skeletal muscles, suggesting its capability to produce antihyperglycemic effects via an insulin-dependent pathway or possibly through activation of AMPK in skeletal muscles [175]. Furthermore, the administration of sulphurenic acid obtained from T. camphoratus resulted in the rise of insulin levels in streptozotocin-induced C57BL/6J diabetic mice, possibly due to an increase in pancreatic Langerhans islets’ size and number upon treatment and caused a notable reduction in the concentration of glycated hemoglobin (HbA1c) [176]. It was noted that sulphurenic acid stimulates the phosphoinositide 3-kinase (PI3K)/Akt pathway, which suppresses hepatic glucose production to result in a hypoglycemic effect. Kuo et al. [177] also reported that dehydroeburicoic acid from T. camphoratus increased the expression of GLUT4 in C2C12 myotube cells and also resulted in 43.6–46.5% decrease in blood glucose level in Streptozotocin-induced C57BL/6J diabetic mice.

Antcin K from T. camphoratus has also been found to exert a hypolipidemic effect by decreasing the expression of fatty acid synthase levels and increasing the hepatic expression levels of carnitine palmitoyltransferase 1A (CPT-1A) and PPAR-α [174, 176]. Eburicoic acid and sulphurenic acid derived from T. camphoratus also increased the expression of PPAR-α in the liver of high-fat diet (HFD)-induced C57BL/6J mice, thus facilitating fatty acid oxidation and reduction of lipid levels [175, 176]. In addition, Kuo et al. [178] reported that Ergostatrien-3β-ol from T. camphoratus reduced visceral adipocyte size and induced hepatic ballooning degeneration. All four above-mentioned compounds were also found to SREBP-1C to downregulate transcription of genes responsible for fatty acid synthesis, suggesting the potent hypolipidemic effects of T. camphoratus [174, 175, 178, 191].

Antioxidant

Ethanolic extract of T. camphoratus fruiting body displayed strong DPPH radical and superoxide dismutase (SOD)-like scavenging activities at levels nearly equivalent and stronger than vitamin C respectively [9]. In DPPH assay, the activity at 4 mg/mL of the extract was around 83%, almost as high as that of vitamin C at 0.5 mg/mL, which demonstrated around 88% activity. In contrast, the extract’s activity at 4 mg/mL in the SOD scavenging assay was around 71–87%, higher than that of vitamin C at 0.5 mg/mL, which demonstrated around 67% activity. The potent antioxidant activities of T. camphoratus were further highlighted in another study where T. camphoratus crude oil and polysaccharide had half maximal effective concentration (EC₅₀) values of 47 µg/mL and 22 µg/mL respectively in DPPH assay, significantly than that of tert-Butylhydroquinone and ascorbic acid at 11.2 µg/mL and 6 µg/mL [179]. Besides that, T. camphoratus mycelium extract recorded strong and dose-dependent scavenging activity, which can be attributed to its high phenolic content, observed to be at 20 mg/g [14]. Furthermore, Li et al. [35] reported that the polysaccharides isolated from T. camphoratus which were enriched with selenium recorded almost double the DPPH and ABTS radical scavenging activity in comparison to the unenriched polysaccharides, thus suggesting the possibility of raising the antioxidant properties of T. camphoratus through modifications of isolated bioactive compounds.

Hepatoprotective

Kumar et al. [180] reported that treatment with antroquinonol and mycelia of Golden-T. camphoratus displayed effective protection of the liver against alcohol-induced damage both in vitro and in vivo, whereby both antroquinonol and mycelia pretreatment considerably and dose-dependently decreased the ethanol-associated rise in alanine aminotransferase (ALT) and aspartate transaminase (AST) after 24 h in oxidative stress-induced HepG2 cells [180]. Furthermore, Chen et al. [181] revealed the potential of antroquinonol from Golden-T. camphoratus to inhibit hepatic lipid accumulation and release of inflammatory cytokines through the upregulation of hepatic adenosine diphosphate (ADP)-activated protein kinase and concurrent downregulation of SREBP1 expression and fatty acid synthase expression.

Hepatoprotective activities have also been found in antrosterol from T. camphoratus, whereby pre-treatment of chronic alcohol liver disease-induced mice could reduce serum/hepatic lipids, increase fecal lipid/bile-acid output, amplify hepatic antioxidant activities, reduce serum alcohol level, and decrease liver inflammation, fibrosis, serum AST/ALT, and TNF-α/IL-1β [182]. These combined findings provide valuable insights into the multifaceted mechanisms underpinning the hepatoprotective role of compounds isolated from T. camphoratus.

Anti-inflammatory

The ethanol extract of T. camphoratus grown on germinated brown rice was reported to inhibit NO, prostaglandin E2 (PGE2), iNOS and COX2 production while inducing p38-MAPK, extracellular signal-related kinases (ERK) and NF-κB in LPS-stimulated RAW264.7 cells [183]. The same study also reported similar observations for the in vivo analysis in addition to the reduction of TNF-α and IL-6 mRNA expression levels in treated dextran sulfate sodium (DSS)-induced mice. Similar findings were also reported by Kuo et al. [184], in which significant inhibition of MMP-1, IL-6, iNOS, and NF-κB were observed in the skin of ultraviolet B-induced mice for topical administration of 25 and 100 μM ergostatrien-3β-ol isolated from T. camphoratus.

Besides, Tsai et al. [185] reported a decrease in gene expressions of iNOS, IL-6, TNF-α and NF-κB along with significantly lowered necrosis and inflammatory cell infiltration (both sub-dermis and epidermis) in skin-flap ischemia damage-induced mice treated with the methanol extract of the wood-cultured fruiting body and solid state-cultured mycelia of T. camphoratus. In addition, acetylantroquinonol B [186] and benzoids [187] were also found to inhibit the NO production in inflammation-induced RAW 264.7 cells, further demonstrating the anti-inflammatory capabilities of T. camphoratus.

Antiviral

A limited amount of research on the antiviral effects of T. camphoratus has been conducted over the past decade. According to He et al. [11], a fraction of the crude ethanol extract of T. camphoratus exhibited notable antiviral activity against the herpes simplex virus type 1 (HSV-1) and herpes simplex virus type 2 (HSV-2), significantly inhibiting the viral replication between 1–4 h upon infection of Vero cells. However, antiviral activity reduced with the addition of the extract after 5 h of infection, suggesting low inhibition of late multiplication of virus [11]. In addition, Chen et al. [188] reported that the pre-treatment of two ethanolic extracts of T. camphoratus inhibited the replication of Dengue virus in Meg-01 cells by increasing the expression of antiviral cytokine interferon alpha (IFN-α) and decreasing the release of pro-inflammatory cytokines IL-6 and IL-8.

Polysaccharides from T. camphoratus were also found to possess anti-Hepatitis B virus (HBV) activity, where polysaccharides from B86 and 35,398 strains most significantly inhibited hepatitis B e-antigen (HBeAg) synthesis, with about 30% antiHBeAg inhibition percentage for both strains at a concentration of 50 µg/mL [189]. Apart from HBV, antrodins A to E, except antrodin B, isolated from T. camphoratus exhibited potent inhibitory effects against the HCV protease, whereby antrodin A had the highest potency with a half-maximal inhibitory concentration (IC₅₀) value of 0.9 µg/mL [190].

Inonotus obliquus

Anticancer

I. obliquus is capable of exerting a wide range of therapeutic properties, as summarized in Table 3, which includes its anticancer activities. I. obliquus has been used in folk medicine for the treatment of cancer [4], including its use to heal lip tumours [192]. In the twentieth century, the remarkable ability of I. obliquus to reduce the number of cancer cases in the population was noticed by the Soviet health authorities [40], leading to increasing amounts of scientific research to be conducted on this medicinal mushroom (Table 3).

Table 3 Health-promoting properties of Inonotus obliquus extracts and bioactive compounds

Aqueous extracts obtained from the fermentation of I. obliquus displayed a dose-dependent inhibition in the growth of HCT-15 cells via the induction of apoptosis [194] and a 51% reduction in B16-F10 melanoma cell proliferation after a 48-h exposure to 750 µg/mL of extract [195]. Further analysis revealed that I. obliquus extract may restrict cell proliferation or stimulate differentiation in B16-F10 cells by causing G0/G1 phase arrest and subsequent apoptosis process that occurs when caspase-3 is activated [195]. Another study using aqueous extracts of I. obliquus exhibited a dose-dependent inhibition in growth of HT-29 cells via induction of apoptosis, where the highest inhibition of 56% was recorded at the concentration of 1.0 mg/mL at the 48 h time-point. [196]. The anticancer properties of the aqueous extract of I. obliquus was also effective in vivo, where a consistent intake of the aqueous extract managed to decrease 25% of the metastatic tumour nodules and reduce 60.3% (Day 16) of tumour growth in 3LL carcinoma-implanted C57BL/6 mice as compared to the control group [6]. Furthermore, Yuan et al. [197] reported that 7 mg/mL of aqueous extract of the fungi exhibited about 33% inhibition in tumour growth in DLD-1 colorectal adenocarcinoma inoculated mice for 36 days.

Apart from aqueous extracts, the ethanol extracts of I. obliquus also exhibit promising anticancer effects. According to Lee et al. [198], the extracts stimulated cell cycle arrest at G1 phase, induced higher levels of p21 and p27, resulted in the inhibition of cyclin-dependent kinase (CDK), and consequently reduced retinoblastoma tumour suppressor protein (Rb) phosphorylation. The advancement of the G1 into S cell cycle was halted as a result of these effects, followed by a suppression of HT-29 cell proliferation. Ethanol extracts obtained from wild sclerotium, cultivated sclerotium, and cultivated fruiting body of I. obliquus demonstrated anticancer effects with inhibition rates ranging from 44.2 to 74.6% [199]. Moreover, Hu et al. [200] reported that DLD- 1 cells are also susceptible to the ethanol and hot water extracts of I. obliquus via the induction of apoptosis and reducing oxidative stress. In addition, in a study conducted by Nakajima et al. [201], methanol extracts from both the fruiting body and sclerotium of I. obliquus exhibited anticancer effects on IMR-90, A549, PA-1, U937, and HL-60 cells, whereby PA-1 cells were the most susceptible to both types of methanol extracts, with the methanol extract from sclerotium displaying more potent cytotoxic effects to all tested cancer cell lines.

Other constituents isolated from I. obliquus have also demonstrated promising anticancer properties. Polysaccharides isolated from I. obliquus were also found to inhibit tumour growth in SGC-7901 tumour-bearing mice [202] and exert anticancer effects in LLC1 cells in both time and dose-dependent manners [92]. Moreover, a triterpenoid named 3β-hydroxylanosta-8,24-dien-21-al induced cytotoxic effects on A549, H1264, H1299, and Calu-6 lung cancer cells with IC₅₀ values of 5.3 µg/mL, 90.9 µg/mL, 128.0 µg/mL and 75.1 µg/mL respectively [203]. These findings collectively highlight the potent anticancer effects of a wide variety of compounds derived from I. obliquus.

Hypoglycemic and hypolipidemic

In addition to its anticancer effects, I. obliquus is also known for its hypoglycemic and hypolipidemic activities. Wang et al. [193] showed that oral administration of I. obliquus polysaccharides (IOPS) (900 mg/kg) could significantly improve glucose tolerance, reduce fasting blood glucose levels, increase hepatic glycogen levels, and alleviate insulin resistance in streptozotocin induced type 2 diabetes mellitus mice. It was also found that the IOPS increased expressions of PI3K-p85, p-Akt (ser473), and GLUT4 to therefore promote glycolysis and inhibit gluconeogenesis [193]. Furthermore, methanol extracts of I. obliquus can significantly improve blood glucose and lipid levels, as well as exert an anti-inflammatory effect in type 2 diabetic mice through downregulation of harmful groups such as Proteobacteria, upregulating levels of beneficial bacteria such as Odoribacter, and promoting short-chain fatty acid levels by increasing abundance of acid-producing bacteria such as Alistipes [204]. Moreover, Lee and Hyun [205] reported that water-soluble melanin complex isolated from I. obliquus were found to increase the insulin-stimulated glucose uptake and exert a dose-dependent increase in Akt phosphorylation and GLUT4 translation into the cytoplasm. In addition, another study by Cha et al. [206] mentioned that a diet supplemented with 50 g/kg fermented powder from I. obliquus was observed to significantly (p < 0.05) lower the glucose level in 100 mL of serum of streptozotocin-induced type 1 diabetes mellitus mice in comparison with supplementation with non-fermented chaga powder and without any supplementation.

According to Yang et al. [207], the administration of I. obliquus polysaccharides was able to decrease the total cholesterol (TC), triacylglycerol (TG), and low-density lipoprotein (LDL) levels, and consequently increased high-density lipoprotein (HDL) levels through the activation of AMPK and induction of fatty acid oxidation. This is consistent with the results obtained from a study conducted by Ye et al. [204] in which mice treated with I. obliquus methanol extract exhibited decreased LDL cholesterol (LDL-C), TC and TG levels, and higher HDL cholesterol (HDL-C) levels (p < 0.01). The polysaccharides treatment could also induce a significant reduction in the mRNA expression of SREBP-1, acetyl-CoA carboxylase (ACC), and fatty acid synthase to further contribute to its hypolipidemic activity [207]. Hypolipidemic effects were also observed in the 250 mg/kg and 500 mg/kg I. obliquus aqueous extract treatment groups, with decreased TC, TG, and LDL-C and increased liver glycogen and HDL-C in high-fat diet-inducedC57BL/6 mice via the regulation of the PI3K/Akt and AMPK/ACC signalling pathways [208]. Similar hypolipidemic effects were also reported in oligosaccharides of I. obliquus via modification of the intestinal bacteria in high-fat fed mice in which the ratio between the population of Firmicutes to Bacteroidetes faecal flora was reduced in treated groups, reducing the production of fatty acids and thus lowering blood lipids [209].

Antioxidant

Two novel isocoumarins found in I. obliquus exhibited significant antioxidant activity in FRAP, DPPH and ABTS assays as compared to Trolox, a potent antioxidative [15]. In addition, the sclerotium and mycelium extracts of I. obliquus exhibited protection from cellular DNA damage from H₂O₂ in healthy human lymphocytes at a similar intensity as natural antioxidants [210]. Another study by Cui et al. [211] found strong antioxidant activities in both the polyphenolic extract and another extract containing triterpenoids and steroids, with more significant activity in the former, suggesting the crucial contribution of phenols to the mushroom’s antioxidative properties.

Five polysaccharides isolated from I. obliquus also displayed antioxidant activities, in which stronger antioxidant activities were observed in the ones with higher uronic acid and proteinous substances content [212]. Furthermore, in a study by Hu et al. [213], it was found that 5 mg/mL of IOPS had a scavenging activity of 82.3% in DPPH assay and 81.3% in hydroxyl radical scavenging assay. Additionally, it also elevated SOD levels and reduced malondialdehyde (MDA) levels in a dose-dependent manner, thus bringing levels of oxidative stress close to normal levels in chronic pancreatitis-induced mice, highlighting the potential therapeutic application of I. obliquus’ antioxidative functions.

Hepatoprotective

A study conducted by Xu et al. [214] investigated the protective effects of polysaccharides isolated from I. obliquus in liver damage induced by Toxoplasma gondii infection in mice, reported a decrease in ALT, AST, MDA and NO levels, with an increase in SOD and glutathione (GSH). Besides, Hong et al. [215] reported that the aqueous extract of I. obliquus resulted in significant protection to tert-butyl hydroperoxide liver damage-induced rat hepatocytes even at a low concentration of 10 µg/mL. Moreover, d-galactosamine intoxicated-normal Chang liver cells experienced 2–2.5 times increase in viability upon treatment with 10⁻⁵ and 10⁻³ g/ L of melanin isolated from aqueous extract of I. obliquus [216]. Consistent findings were also obtained in vivo where decrease in fat buildup, steatosis, necrosis, and normalization of serum cholinesterase, gammaglutamyl transpeptidase, total protein and unconjugated bilirubin levels were observed in carbon tetrachloride liver damage induced-Sprague Dawley rats (Fig. 4).

Fig. 4

Hepatoprotective properties possessed by Inonotus obliquus

Anti-inflammatory

The extract from I. obliquus grown on germinated brown rice was found to inhibit proinflammatory mediators NO, PGE2, iNOS, COX-2, TNF-α, IL-1β, and IL-6 in LPS-stimulated RAW 264.7 macrophages [217]. Besides, Ma et al. [101] reported that the petroleum ether extract of I. obliquus resulted in approximately 84.6% and 96.9% reductions in NO production and NF-κB luciferase activity respectively in LPS-stimulated RAW 264.7 macrophages, while the ethyl acetate extract stimulated 78.2% and 96.6% reductions in NO production and NF-κB luciferase activity accordingly [101]. Moreover, more than 90% suppression in histamine-induced TNF-α was discovered in histamine inflammation-induced-C57BL/6 mice upon treatment with the methanol extract of I. obliquus, thus further highlighting the anti-inflammatory properties of I. obliquus [218].

Antiviral

Shibnev et al. [219] reported that the infective property of hepatitis C virus was significantly reduced by I. obliquus water extracts, which exhibited a high antiviral effect with low cytotoxicity on porcine embryo kidney cells (SPEV), thereby shielding all of SPEV cells post-infection from virus-induced death at a level of 0.1 TCD50/cell. I. obliquus water extracts were also able to inhibit the replication of SARS-CoV-2 (nCoV/Victoria /1/2020 strain) in Vero E6 and Vero cell cultures [220], which may be explained by its significant binding affinity with the viral S1-carboxy-terminal of the SARS-CoV-2 receptor-binding domain, producing multivalent hydrogen and non-polar interactions (7.4 to 8.6 kcal/mol) [221].

Aqueous and water-alcohol extracts of I. obliquus have also been shown to possess antiviral effects against the human immunodeficiency virus type 1 (HIV-1) at a concentration of 5.0 µg/mL against virus-infected lymphoblastoid cells culture MT-4 [12]. Furthermore, I. obliquus alcohol-water pilat extract demonstrated significant in vitro anti-HSV-1 activity at concentrations ranging from 4.5 × 10^–5 to 7.5 × 10⁰ mg/ml [222]. The observed antiviral property could also be observed in vivo, whereby 90% of HSV-2 infected albino mice survived through prior intraperitoneal administration of 0.4 to 2 mg of I. obliquus aqueous extract [223].

In addition, according to Tian et al. [224], IOPS was found to exhibit antiviral effect against a large spectrum of feline viruses, which include the feline influenza virus (FIV), feline calicivirus (FCV), feline panleukopenia virus (FPV), feline herpesvirus 1 (FHV-1) and feline infectious peritonitis virus (FIPV) by interfering with the virions and/or cell receptors, thus preventing the viral entrance into the cell. This suggests the strong antiviral properties of not only crude extracts obtained from I. obliquus, but also isolated components such as polysaccharides as demonstrated above.

Tropicoporus linteus

Anticancer

The anticancer properties of Tropicoporus linteus and their underlying mechanisms have been widely studied in recent years (Fig. 5). A comparison between ethanol and water extracts of T. linteus, P. igniarius, and P. nigricans showed that the ethanol extract of T. linteus exerts strong cytotoxic effects against cholangiocarcinoma cells, with percent cell inhibition reaching as high as 98.92 ± 0.22 [225]. Besides, the ethanol extract of this mushroom exerted a significant dose-dependent inhibition in MDA-MB-231 cells, where an IC₅₀ value of 40 mg/mL was obtained at the 24 h time point [226]. A notable observation is that 30 mg/mL of this extract alone exerted 16.7% inhibition while 10 µg/mL of 5-fluorouracil alone exerted 12.6% inhibition in cell growth, but this value spiked significantly to 53% when both of them were administered together (Table 4).

Table 4 Health-promoting properties of Tropicoporus linteus extracts and bioactive compounds

Park et al. [227] reported that the ethyl acetate extract of T. linteus grown in germinated brown rice induced apoptosis in HT-29 cells via the induction of cell cycle arrest at the G0/G1 phase and DNA fragmentation. HT-29 cells were also susceptible to the n-hexane layer of ethyl acetate extract from T. linteus which showcased potent anticancer effects with an IC₅₀ of 69.8 µg/mL at the 48 h time point [228]. Moreover, the methanol extract of T. linteus also displayed anticancer effects in SW-480 and HCT-116 cells where an increase in anti-migratory marker E-cadherin and a decrease in pro-migratory/pro-invasive proteins N-cadherin and Vimentin were observed with higher selectivity towards SW-480 cells [229]. Besides, extracts of T. linteus grown on germinated brown rice could increase the sensitivity of KRAS-mutated SW480 colon cancer cells to cetuximab with a reduced number of colonies in clonogenic assay and increased apoptotic rate [230]. Recent research has also revealed that T. linteus possesses potent anti-breast cancer proliferative activity by downregulating marker of proliferation Kiel 67 (MKI67), Human epidermal growth factor receptor 2 (HER2), epidermal growth factor receptor (EGFR), murine double minute 2 (MDM2), TNFα, and phosphatidylinositol-4,5-bisphosphate 3-kinase catalytic subunit alpha (PI3KCA) expression [245].

A novel polysaccharide isolated from T. linteus exhibited stronger inhibitory effects than 5-fluorouracil on murine sarcoma cancer cells (S-180) at 12 and 24 h, with inhibition rates of up to 93% at 72 h at a concentration of 200 µg/mL [126]. The polysaccharide’s potent in vitro anticancer properties were found to be mediated by a decreased expression of Bcl-2 with a rise in pro-apoptotic Bax protein expression, indicating that the observed anticancer effect was exerted via stimulation of apoptosis. Furthermore, two bioactive compounds (PL-ES and PL-I-ES) isolated from T. linteus were also found to exert apoptosis-associated anticancer effects on a total of 10 different cancer cell lines where 100 g/mL of PL-ES could suppress growth in all 10 cancer cells, while 100 and 250 g/mL of PL1 was able to cause significant growth reduction in four and seven cancer cells types respectively [231].

Besides from the above mentioned constituents, hispolon from T. linteus also exhibited anticancer effects in MCF-7, MDA-MB-231, T24, and J82 cells where it suppressed p53 mutant (MDA-MB-231, T24, and J82) and wild-type (MCF7) cells regardless of p53 status [232]. The extract induced apoptosis in the mentioned cancer cells, which was found to be mediated via chromatin condensation and an increase in poly (ADP-ribose) polymerase (PARP). Additionally, Liu et al. [233] reported that Atractylenolide I isolated from T. linteus was effective in gastric cancer cachexia management, where it was found to be significantly more effective than fish-oil-enriched nutritional supplementation at improving appetite, Karnofsky performance status, and decreasing proteolysis-inducing factor positive rates, suggesting the use of T. linteus as not only an anticancer agent, but also as a functional food during cancer treatment (Fig. 5).

Fig. 5

Reported mechanisms through which Tropicoporus linteus exert anticancer properties

Hypoglycemic and hypolipidemic

The hypoglycemic properties of T. linteus extract from mycelia of solid-state culture was observed in diabetic rat models by Liu et al. [10], as evidenced by decreased serum glucose, glycated serum proteins, and insulin levels along with increased expressions of glucokinase and GLUT2 8 weeks after treatment with 120 and 600 mg/kg. A similar study by Kim et al. [234] also found that exo-polymers produced from the submerged cultures of T. linteus were also able to induce hypoglycemic effects on streptozotocin-induced diabetic rats, which was proposed to be through reparation of streptozotocin-exposed pancreatic β-cells, thus increasing insulin secretion leading to effective clearance of blood glucose. This finding is also supported by Sonawane et al. [246], where the crude polysaccharide of another mushroom from the Phellinus family, named Phellinus badius was also expected to exert the same effects on streptozotocin-induced diabetic rats. Moreover, polysaccharides isolated from T. linteus were found to improve insulin resistance via amplification of the population of short-chain fatty acids (SCFAs)-producing bacteria in the gut of streptozotocin induced-type 2 diabetes mellitus mice, which resulted in increased levels of SCFA that sustained the intestinal barrier function and thus caused reduction in LPS content in blood [125]. Consistent finding was also reported by Zhao et al. [124] in alloxan-induced diabetic mice, where mean percentage decrease in blood glucose levels of 22.35%, 16.35%, and 15.19% at concentrations of 100, 200, and 400 mg/kg of I. obliquus polysaccharides respectively was recorded.

Besides from its hypoglycemic properties, T. linteus extract from mycelia of solid-state culture is also capable of exerting hypolipidemic effects in HFD-induced rat models, with significant reductions in the levels of TG, TC, free fatty acids, and LDL-C in groups treated with 120 mg/kg and 600 mg/kg of the extract [10]. The extract’s hypolipidemic activities are proposed to be mediated through regulation of the expression of genes involved in lipid transport and metabolism, including an increase levels of fatty acid β-oxidation-associated genes acyl-CoA oxidase 1 (ACOX1) and CPT1A, elevation of amount of LDL receptors, and reduction of rate-limiting enzyme 3-hydroxy-3-methylglutaryl-CoA reductase (HMGCR), which together contribute to its potent hypolipidemic effects [125]. Similarly, administration of ethyl acetate fraction from T. linteus mycelia (PL-EA) for four weeks was able to improve body weight, hepatic lipid accumulation, and fasting blood glucose levels in HFD-induced mice through upregulating peroxisome proliferator-activated receptor gamma coactivator 1-alpha (PGC-1α) and adiponectin while downregulating glucokinase and SREBP-1c [138]. Furthermore, the major purified compounds of hispidin and hypholomine B in PL-EA significantly reduced the level of oleic and palmitic acids-induced lipid accumulation in HepG2 cells to contribute to the alleviation of non-alcoholic fatty liver in treated groups.

Antioxidant

According to Lee et al. [235], hispidin isolated from T. linteus was found to protect MIN6N β-cells of the pancreas from oxidative stress, where treatment with hispidin between the range of 10–70 µM revealed notable ROS scavenging activity in a dose-dependent manner, with the highest concentration having an activity of about 65%. The antioxidant properties of the extract were found to be mediated by an inhibition of caspase-3 activity, thus preventing the initiation of oxidative-stress induced apoptosis [235]. In addition, three constituents obtained from the culture broth of T. linteus, namely caffeic acid, inotilone, and 4-(3,4-Dihydroxyphenyl)-3-buten-2-one, were found to possess potent antioxidant activity in DPPH, ABTS and FRAP assay, while (2E,4E)-γ-Ionylideneacetic acid, Phellilane H, and (2E,4E)-4′-Hydroxy-γ-ionylideneacetic acid showed weak reducing power [133]. It should also be noted that caffeic acid, inotilone, 4-(3,4-Dihydroxyphenyl)-3-buten-2-one recorded higher antioxidant activity than butylated hydroxyanisole and Trolox in FRAP assay.

Three polysaccharides isolated from T. linteus exerted strong DPPH radical scavenging activity of between 58 to 72% at a concentration of 2 mg/mL [119]. Another study reported that hot water polysaccharide extracts of T. linteus fruiting bodies demonstrated notable antioxidant capabilities, with DPPH scavenging activities stronger than that of ascorbic acid at 5 mg/mL and above [236]. In addition, the stronger antioxidant activity of T. linteus was demonstrated by a significantly lower EC₅₀ value than that of Aspergillus brasiliensis and Agaricus bisporus, further highlighting the potent antioxidant effects of T. linteus [236].

Hepatoprotective

Wang et al. [237] reported that the polysaccharides of T. linteus exhibited protective effects on thioacetamide liver fibrosis-induced mice via the regulation of the heat shock, oxidative stress, amino acid and nucleic acid metabolic pathways. Extracts isolated from T. linteus grown on germinated rice were also found to be capable of reducing peroxidation products in the liver of carbon tetrachloride-induced mice and decreasing cytochrome P450 2E1 (CYP2E1) protein expression [238]. Moreover, a decrease in glutamic transaminase enzyme released was also observed in H₂O₂-injured rat hepatocytes treated with 100 µg/ml methanol extract of T. linteus mycelial culture [239]. Further investigations revealed that the ethyl acetate fraction from the methanol extract of mycelial culture displayed 68.9 ± 5.3% protection to H₂O₂-injured hepatocytes and 46.8 ± 3.9% protection to galactosamine-injured hepatocytes, demonstrating the potent hepatoprotective effects of T. linteus.

Anti-inflammatory

T. linteus polysaccharides have been shown to substantially reduce the expression of key inflammatory cytokines, IL-6, IL-1β, and TNF-α, both in vivo in murine models induced with DSS and in vitro in LPS-stimulated RAW 264.7 macrophages through modulation of the MAPK and PPAR signaling pathways [115]. Similar conclusions were made by Shin et al. [240], who demonstrated the ability of T. linteus to deactivate NF-κB signaling through the inhibition of p38 MAPK, subsequently suppressing both inflammatory factors and elements associated with cartilage matrix degradation, thereby exerting a potent chondroprotective effect through simultaneous mitigation of ROS production and inflammation [240].

Extracts from T. linteus growth on germinated brown rice could inhibit NO and PGE2 production as well as reduce iNOS, NF-κB, COX-2, and TNF-α expressions to ameliorate pathological changes of colitis [241], while T. linteus grown on Panax ginseng media could suppress phosphorylation of spleen associated tyrosine kinase, GRB2 associated binding protein 2 (GAB2), and extracellular signal-regulated kinases required for degranulation and release of inflammatory cytokines [242]. Similar findings were obtained in a study by Lin et al. [145], where T. linteus-fermented broth exhibited dose-dependent inhibition of NO, NF-κB, and TNF-α in RAW264.7 cells and murine primary peritoneal exudate macrophages. A notable observation is the presence of high amounts of hispolon in the sample that showed the strongest anti-inflammatory activities, suggesting the important role of this compound in the inflammation-reducing functions of T. linteus [145]. Another compound isolated from T. linteus, inotilone, has been demonstrated to possess potent anti-inflammatory properties, capable of inhibiting NO production, protein expression of iNOS, NF-κB, and MMP-9, and suppression of LPS-induced ERK, c-Jun N-terminal kinase (JNK), and p38 phosphorylation in RAW264.7 macrophages [243]. Taken together, the abovementioned studies highlight the potent anti-inflammatory abilities of T. linteus and its potential for therapeutic applications.

Antiviral

Inhibition studies revealed a dose-dependent inhibitory activity of T. linteus methanol extract on α-glucosidase, a crucial component for the morphogenesis of enveloped viruses [244]. Due to the similarity between syncytium formation of Newcastle disease virus (NDV) and HIV, the inhibition effect of the extract on hemagglutinin-neuraminidase protein of NDV expressed on baby hamster kidney cells were measured, leading to the finding that T. linteus methanol extract was capable of suppressing NDV-induced syncytium formation at 12.5 µg/mL, similar to that of α-glucosidase inhibition [244]. This suggests the potential use of T. linteus against viruses such as HIV, HBV, and dengue virus, which are known to be highly sensitive to glucosidase inhibition.

Besides glucosidase, two constituents of T. linteus fermentation broth, inotilone as well as 4-(3,4-dihydroxyphenyl)-3-buten-2-one demonstrated strong neuraminidase inhibitory effects [13]. Microscopic findings revealed that 10 µM of both isolated constituents inhibited the formation of visible cytopathic effects, with IC₅₀ values lower than that of Oseltamivir (61 and 52 µM respectively compared to 64 µM), suggesting the potential of T. linteus-derived constituents as stronger neuraminidase inhibitors of Influenza A H1N1 virus than the commonly used Oseltamivir treatment [13]. In addition, recent findings by Li et al. [35, 38] reported that hispidin and hypholomine B from the mycelial ethanol extract of T. linteus reduced the expression of angiotensin-converting enzyme 2 (ACE2) gene in HepG2 cells and blocked the spike receptor-binding domain to minimize the entry of the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) virus, further demonstrating the strong antiviral and therapeutic potential of T. linteus for viral infections.

Medical evidence through clinical trials

Taiwanofungus camphoratus

The promising health-promoting and therapeutic effects of T. camphoratus have been demonstrated through both in vitro and in vivo experiments, as discussed previously. In recent years, clinical trials have been conducted to further validate the pharmacological activities of the medicinal mushroom in the biological conditions of the human body (Table 5).

Table 5 Clinical trials carried out on Taiwanofungus camphoratus, Inonotus obliquus, and Tropicoporus linteus

Chen et al. [247] found that 8 weeks of oral T. camphoratus mycelium treatment could induce significant reductions in systolic and diastolic blood pressure, which was proposed to be through interaction with the renin-angiotensin system to lower blood pressure by inhibiting renin secretion. The historical use of T. camphoratus as a traditional Chinese medicine for treating hypertension further substantiates these contemporary findings [255]. Golden-T. camphoratus administration was also capable of reducing AST, ALT, and TG levels with no significant effects on general safety parameters, suggesting the use of Golden-T. camphoratus as a safe and effective hepatoprotective agent [248].

In addition, a study conducted by Tsai et al. [249] to explore the combined effects of T. camphoratus treatment and chemotherapy found that although significant enhancements in fatigue or quality of life were not observed, T. camphoratus did contribute to improved sleep quality. Nevertheless, the potential benefits were clouded by adverse effects, including gastrointestinal discomfort and a reduction in platelet counts within a month of treatment, where the precise relationship between these effects and T. camphoratus remains to be fully elucidated. Although prior in vitro and in vivo studies such as that conducted by Huang et al. [256] have highlighted the capability of T. camphoratus to enhance the sensitivity of colon cancer cells to chemotherapy, these promising results did not translate directly to clinical trials, as evidenced by the divergent outcomes observed by Tsai et al. [249] due to potentially different interactions with the complexities of human clinical contexts. This underlines the need for cautious interpretation and further rigorous investigation to ascertain these findings in clinical applications.

Inonotus obliquus

Numerous in vitro and in vivo studies have highlighted the potential health benefits and therapeutic effects of I. obliquus, thus prompting the initiation of several clinical trials to explore the pharmacological activities of I. obliquus in human subjects.

In a study undertaken by Dosychev and Bystrova [250], it was found that 38 patients experienced a complete disappearance of psoriatic eruptions, while 8 patients exhibited significant improvement in related symptoms. This outcome resonates with a related study that highlighted the immune-promoting effect of I. obliquus, indicating its suitability in the context of molecular mechanisms of action in immunological disease driven by TNF-α, which pertains to conditions such as psoriasis [257]. Additionally, noticeable relief or complete resolution of gastrointestinal tract symptoms was observed [250], which agrees with an in vivo investigation conducted by Hu et al. [258] that reported that I. obliquus polysaccharide contributes to shaping the gut microbiota composition toward a healthier profile at the genus level.

An investigation carried out by Fedotov and Yu [251] found that I. obliquus was capable of reducing pain related to peptic ulcers, with more substantial effects seen at higher doses. However, interestingly, the cessation of I. obliquus treatment resulted in the return of pain levels to their original state. These findings are aligned with a related study conducted on rats which demonstrated the effective antiulcer activity of I. obliquus, further validating the therapeutic effect of this medicinal mushroom [259].

Despite its widespread global utilisation and the multitude of experiments conducted, the available corpus of peer-reviewed literature encompasses solely two clinical studies, both conducted over four decades ago, as previously indicated [250, 251]. It is important to underscore that no controlled trials assessing the safety of I. obliquus were identified, and no pertinent studies were found to be registered on Clinicaltrials.gov. Analogous to many mushroom supplements, the prevailing evidence concerning safety and efficacy heavily relies on the extensive historical use of I. obliquus. In light of this, further comprehensive studies, particularly through rigorous clinical trials, are imperative to establish a more nuanced and comprehensive understanding of I. obliquus's impact on the human body [260].

Tropicoporus linteus

A recent randomized, double-blind, placebo-controlled pilot trial conducted on participants with a history of upper respiratory infections validated the immunomodulatory effect of T. linteus as evidenced by heightened natural killer cell activity and elevated IL-6, immunoglobulin G1 (IgG1), IgG2, and IgM levels [252]. Another pilot clinical study revealed the ability of T. linteus to relieve pain resulting from knee osteoarthritis and return markers of inflammation to normal values, suggesting the potential of T. linteus in alleviating knee arthritis symptoms [253]. This is in line with the observation made by Kim et al. [261] where T. linteus was able to suppress collagen-induced arthritis in vivo by reducing anti-type II collagen IgG and IgG2a antibodies as well as various cytokines including IL-12, TNF-α, and IFN-γ in mice, further highlighting the pivotal role of T. linteus in preventing and treating joint inflammation.

In a study conducted by Sung et al. [254], patients with pancreatic cancer who underwent pancreatectomy were recruited over the course of 19 years and retrospectively analysed to examine the impact of T. linteus on adherence to postoperative adjuvant treatment. Remarkably, T. linteus medication increased patient adherence to postoperative chemotherapy to contribute to overall long-term oncologic outcomes, further highlighting the potential application of T. linteus as not only an anticancer agent as evidenced by in vitro and in vivo studies, but also as an adjuvant to improve outcomes to conventional chemotherapy.

Conclusion

This review has extensively examined the diverse biological activities, therapeutic effects, and pharmacological impacts of three notable mushrooms: T. camphoratus, I. obliquus, and T. linteus. Throughout numerous in vitro and in vivo studies, these mushrooms have revealed their potential through bioactive compounds that hold promise for human well-being. The growing interest in natural products as alternative treatments for conditions such as cancer and viral infections is evident from the increased scholarly and societal attention. Nonetheless, it is imperative to underscore the need for further comprehensive clinical trials that focus on safety, toxicity, and potential risks. Such investigations would offer robust scientific foundations and practical insights for optimising the biological effectiveness of these mushrooms while minimising any adverse effects. This will also encourage the development of mushroom products in not only medicinal applications, but also its exploitation in the cosmetic industry due to their excellent antioxidant, anti-aging, and moisturizing properties, ensuring a wider accessibility to the manifold benefits these mushroom species offer to a broader population.