Purported medicinal properties of chaga mushroom
Chaga has been found to contain a host of pharmacologically active compounds that beneficially affect human health (Zjawiony 2004, De Silva et al. 2013). The biological activity of I. obliquus is mainly due to the presence of several polysaccharides, constituting the following sugars: rhamnose, arabinose, xylose, mannose, glucose, and galactose (Hu et al. 2017). Additionally, in the last decade, several studies have reported biological activities of I. obliquus such as anticancer, antioxidation, anti-inflammatory, antidiabetic and enhancement of immunity (Choi et al. 2010). Remarkably, a number of studies demonstrates little or no side effects during use in disease treatment (Wasser 2002, Choi et al. 2010, Elkhateeb et al. 2019). The biological activities of I. obliquus are discussed below.
Antioxidant activity of chaga
Various compounds extracted from Chaga have been reported to exhibit an antioxidant activity. Nakajima et al. (2007) illustrated superiority of the antioxidant activity (both superoxide and hydroxyl radicals scavenging activities) of a hot water extract of Chaga in comparison with those of other medicinal fungi namely Agaricus blazei mycelia, Ganoderma lucidum and Phellinus linteus. Further determination of the antioxidant potential of the isolated fruiting body (spore-generating mass) and Sclerotium (Chaga) revealed that an 80 % methanolic extract of the fruiting body had a higher potential than that of Chaga decoction.
Antidiabetic - chaga
Chaga extracts (CE) function as an antidiabetic through the lowering of blood glucose levels. Polysaccharides, which represent one of the main components of CE are capable of inhibiting alpha-glucosidase, a carbohydrate-hydrolysing enzyme. Hence, CE may act as a hypoglycemic agent by retarding glucose absorption in digestive organs and thus preventing hyperglycemia following meals (Chen et al. 2010, Lu et al. 2010, Wang et al. 2017). Sun et al. (2008) and Xu et al. (2010), reported that polysaccharides of I. obliquus are capable of reducing glucose, triglycerides, fatty acids, and cholesterol levels in blood.
Anti-inflammatory chaga mushroom
Causes of inflammation can range from wounds, burns, infections, stress, free radicals, radiation and allergies, to immune system disorders. Drugs reducing inflammation are called anti-inflammatories. Van et al. (2009) tested several different types of extractions from Chaga, for their ability to reduce inflammation. All of those tested significantly inhibited inflammation, including a water-based polysaccharide extract and an ethanol-based extract. Kim et al. (2007) and Choi et al. (2010) found similar results with ethanol extracts.
Anticancer activity of chaga
The anticancer activity of CE is perhaps the most widely reported health benefit and that which has received the most interest. The cytotoxic and/or apoptotic effects of CE have been demonstrated in numerous in vitro studies in cancer cell lines, including the human colon cancer cells and the human hepatoma HepG2 cells (Youn et al. 2008). Polysaccharides isolated from I. obliquus sclerotium have a direct antitumor effect due to protein synthesis inhibition in tumour cells. Also, polysaccharides derived from the mycelium of I. obliquus function by activating the immune system. Due to the limited toxicity of these substances, both extracts as well as isolated and purified chemicals may be a good alternative to current chemotherapy and have potential for a role in cancer prevention (Staniszewska et al. 2017). Heteropolysaccharides and homoglucans isolated from the sterile conk as well as endopolysaccharides present in the mycelium differ in the mechanism of antitumor activity; polysaccharides from sterile conks act directly on the tumour cells and endo-polysaccharides act indirectly by activating the immune system in a way similar to bacterial lipopolysaccharide (Kim et al. 2006). The triterpenoid inotodiol showed the strongest anti-proliferative effect on breast cancer Walker 256 cell line (Nakata et al. 2009). Kang et al. (2015) reported that ergosterol peroxide acts as an antiproliferative agent and also inhibits the colony formation ability of tumour cells HCT116, HT-29, SW620 and DLD-1 cell lines of colon. The Ergosterol peroxide from I. obliquus exhibits anticancer activity by down-regulation of the β-catenin pathway in colorectal cancer and it shows that it down-regulated β-catenin signalling; this proves that I. obliquus can be developed as a promising medicine to treat colon cancer (Kang et al. 2015). Nakajima et al. (2009) show that phenolic compounds of methanolic I. obliquus extract demonstrate a target toxicity against several lines of cancer cells and the absence of cytotoxic effects against normal cells. Summary of identified medicinal compounds and their action Over 200 compounds have been extracted and identified from I. obliquus (Rogers 2011). These compounds belong to various chemical groups such as lipids, carbohydrates, polyphenols, and terpenes. The list of compounds extracted from I. obliquus includes but are not limited to β-sitosterol, fecosterol, episterol, β-glucans, xylogalactoglucose, phelligridins D, 3,4-dihydroxybenzalacetone, inonoblins A, vanillic acid, syringic acid, ferulic acid, trametenolic acid, p-hydroxybenzoic acid, foscoperianol D. Some of the biologically active compounds extracted from I. obliquus actually originate from the host tree itself and these include betulin, betulinic acid and such compounds are absent in cultivated strains grown in the laboratory. Some of the biologically active compounds extracted from I. obliquus are listed in the table below:
| Compound | Chemical group | Biological activity |
| Betulin | Terpenes | Antibacterial, protective effects against cadmium induced cytotoxicity |
| Betulinic acid | Terpenes | Antibacterial, anti-malarial, anti-inflammatory, anti-HIV activities and cytotoxicity against a variety of tumor cell lines |
| Inotodiol | Triterpenes | Anticancer, inhibits cell proliferation |
| Lupeol | Triterpenes | Anti-inflammatory and anti-cancer |
| Caffeic acid | Polyphenol | Anti-cancer, inhibits cell proliferation |
| Trametenolic acid | Sterol | Anti-inflammatory |
| Melanin | Melanins | Antioxidant, protect DNA from damage |
| 3,4-dihydroxybenzalacetone | Polyphenol | Anticancer, regulates expression of genes promoting, anti-apoptosis, and cell proliferation. |
| Glucans | Carbohydrates | Immune modulator |
| Ergosterol peroxide | Sterol | Anticancer, antimicrobial, immunosuppressive |
| Inonoblin A | Polyphenol | Antioxidant |
| Phelligridin D | Polyphenol | Antioxidant, anti-inflammatory |
Courtesy of Thoma & al., 2020 Sydowia: Chaga (Inonotus obliquus): a medical marvel but a conservation dilemma?
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