Boletus obliquus Ach. ex Pers. (1801)
Inonotus obliquus, commonly known as chaga mushroom (a Latinisation of the Russian term 'чага'), is a fungus in Hymenochaetaceae family. It is parasitic on birch and other trees. The sterile conk is irregularly formed and has the appearance of burnt charcoal. It is not the fruiting body of the fungus, but a mass of mycelium, mostly black due to the presence of massive amounts of melanin. The fertile fruiting body can be found very rarely as a resupinate (crustose) fungus on or near the clinker, usually appearing after the host tree is dead. I. obliquus grows in birch forests of Russia, Korea, Eastern and Northern Europe, northern areas of the United States, in the North Carolina mountains and in Canada.
The name chaga (pronounced "tsjaa-ga") comes from the Russian word of the mushroom (anglicized from czaga), which in turn is purportedly derived from the word for the fungus in Komi-Permyak, the language of the indigenous peoples in the Kama River Basin, west of the Ural Mountains. It is also known as the clinker polypore, cinder conk, black mass and birch canker polypore.
In Norwegian, the name is kreftkjuke' which literally translates as "cancer polypore", referring to the fungus' appearance or to its alleged medicinal properties. In Finnish, the name is pakurikääpä, combined from pahkura and kääpä translating as "wart polypore".
In England and Canada, it is known as the sterile conk trunk rot of birch, which refers to the fruiting bodies growing under the outer layers of wood surrounding the sterile conk once the tree is dead, to spread the spores. In France, it is called the carie blanche spongieuse de bouleau (spongy white birch tree rot), and in Germany it is known as Schiefer Schillerporling (slate Inonotus). The Dutch name is berkenweerschijnzwam (birch glow mushroom).
Chaga has been used as a folk remedy in Russia and Siberia since the 16th century. According to the Memorial Sloan–Kettering Cancer Center, "no clinical trials have been conducted to assess chaga's safety and efficacy for disease prevention or for the treatment of cancer, cardiovascular disease, or diabetes". They caution that the mushroom extract can interact with other drugs.
Chemical analysis shows that chaga mushroom contains a range of secondary metabolites, including phenolic compounds such as melanins, and lanostane-type triterpenes, which include a small percentage of betulinic acid.
Geographically this fungus is mostly found in very cold habitats. It grows very slowly, suggesting it is not a reliable source of bioactive compounds in the long run. Attempts at cultivating this fungus all resulted in a reduced and markedly different production of bioactive metabolites. Secondary metabolites were either absent or present in very different ratios, and in general showed significantly less potency in cultivated Chaga. Cultivated Chaga furthermore results in a reduced diversity of phytosterols, particularly lanosterol, an intermediate in the synthesis of ergosterol and lanostane-type triterpenes. This effect was partially reversed by the addition of silver ion, an inhibitor of ergosterol biosynthesis.
Additionally, the bioactive triterpene betulinic acid is completely absent in cultivated Chaga. In nature Chaga grows pre-dominantly on birches, and birch bark contains up to 22% of betulin. Betulin is poorly absorbed by humans, even when taken intravenously; its bioavailability is very limited. However, the Chaga mushroom converts betulin into betulinic acid, and many internet sources state Chaga's betulinic acid is bioavailable, even when taken orally. Unfortunately there is no research that confirms this claim.
Chaga dietary supplements
In China, Japan and South Korea, extracts of chaga and other mushrooms from the family Hymenochaetaceae are being produced, sold and exported as anticancer medicinal supplements. The main bioactive ingredient in these extracts are usually (1>3)(1>6) Beta-D-glucans, a type of water-soluble polysaccharide. The biologic properties of crude preparations of these specific β-D-glucans have been subject of research since the 1960s.
Russian literature Nobel Prize laureate Alexandr Solzhenitsyn wrote two pages on the medicinal use and value of chaga in his autobiographical novel, based on his experiences in a hospital in Tashkent, Cancer Ward (1968).
Chaga is also known as Tinder fungus or True Tinder Fungus, due to its use as an excellent tinder for primitive fire starting techniques, particularly for catching sparks produced by the flint-and-steel method (as an alternative to char-cloth, and is also sometimes used with a fire piston or bow-drill.
Inonotus obliquus is sometimes confused with Fomes fomentarius, also known as False Tinder Fungus, as both species are useful as tinder, and both are often referred to as tinder fungus.
Chaga is traditionally grated into a fine powder and used to brew a beverage resembling coffee or tea. For medicinal use, an extraction process is needed to make at least some of the bio-active components bioavailable. These bio-actives are found in the mostly indigestible chitin cell walls of the chaga. Humans lack the enzyme chitinase, so cannot fully digest raw mushrooms or their derivatives, and the digestive process works too fast for the stomach acid to take effect. Scientific studies and research are in general also based on highly concentrated extracts, and traditional Russian usage is also based on a form of hot-water extraction (by preparing zavarka).
Currently, three extraction processes are used, each with a different outcome.
- Hot water extraction is the most common and the cheapest method. It can be compared to the traditional tea-making process. All water-soluble components will be present in the resulting extract. Water-insoluble components, such as phytosterols, betulinic acid and betulin, will be absent. Several extraction rounds combined with modern pharmaceutical techniques can result in high levels of polysaccharides, up to almost 60%. The ß-D-glucans, the bio-active part of these polysaccharides, might add up to ±20 %. Polyphenolic components are water-solubles and will also be present.
- Ethanol or methanol extraction isolates the water-insoluble components, betulinic acid, betulin and the phytosterols. This extraction process is in general used as a second step after hot-water extraction, since ethanol alone will not break down chitin effectively - heat is essential.
- Fermentation is the most time-consuming, so is the most expensive; this method is not used very often. Because fermentation methods are not standardized (many types of bacteria and fungi can be used in the process), the outcome is also not standardized.
Extracts with a therapeutic value usually combine two methods, usually hot water and ethanol extraction. This will result in all bioactive components being present. Cheap, mass-produced extracts are in general hot water, low percentage (4-20%) polysaccharide extracts with limited therapeutic value. The information on the supplements' label will usually reveal inclusion or exclusion of components. However, the majority of mushroom dietary supplements that are sold are non-extracted, being the cheapest option. To achieve at least some therapeutic effects the consumer has to make a tea from it.
- "Inonotus obliquus (Ach. ex Pers.) Pilát 1942". MycoBank. International Mycological Association. Retrieved 2011-10-11.
- Needham, Arthur (2005-12-16). "Clinker Polypore, Chaga". Retrieved 10 October 2011.
- Youn, Myung-Ja; Kim, JK; Park, SY; Kim, Y; Kim, SJ; Lee, JS; Chai, KY; Kim, HJ; Cui, MX; So, HS; Kim, KY; Park, R (2008). "Chaga mushroom (Inonotus obliquus ) induces G0/G1 arrest and apoptosis in human hepatoma HepG2 cells". World Journal of Gastroenterology 14 (4): 511–7. doi:10.3748/wjg.14.511. PMC 2681140. PMID 18203281.
- "Chaga Mushroom". Memorial Sloan–Kettering Cancer Center. 18 July 2011. Retrieved August 2013.
- Rzymowska, J (1998). "The effect of aqueous extracts from Inonotus obliquus on the mitotic index and enzyme activities". Bollettino chimico farmaceutico 137 (1): 13–5. PMID 9595828.
- Mizuno, Takashi; Zhuang, Cun; Abe, Kuniaki; Okamoto, Hidehumi; Kiho, Tadashi; Ukai, Shigeo; Leclerc, Sophie; Meijer, Laurent (1999). "Antitumor and Hypoglycemic Activities of Polysaccharides from the Sclerotia and Mycelia of Inonotus obliquus (Pers.: Fr.) Pil. (Aphyllophoromycetideae)". International Journal of Medicinal Mushrooms 1 (4): 301. doi:10.1615/IntJMedMushr.v1.i4.20.
- Cui, Y; Kim, DS; Park, KC (2005). "Antioxidant effect of Inonotus obliquus". Journal of Ethnopharmacology 96 (1–2): 79–85. doi:10.1016/j.jep.2004.08.037. PMID 15588653.
- Kim, Yong Ook; Han, Sang Bae; Lee, Hong Woen; Ahn, Hyo Jung; Yoon, Yeo Dae; Jung, Joon Ki; Kim, Hwan Mook; Shin, Chul Soo (2005). "Immuno-stimulating effect of the endo-polysaccharide produced by submerged culture of Inonotus obliquus". Life Sciences 77 (19): 2438–56. doi:10.1016/j.lfs.2005.02.023. PMID 15970296.
- Kim, Yong Ook; Park, Hae Woong; Kim, Jong Hoon; Lee, Jae Young; Moon, Seong Hoon; Shin, Chul Soo (2006). "Anti-cancer effect and structural characterization of endo-polysaccharide from cultivated mycelia of Inonotus obliquus". Life Sciences 79 (1): 72–80. doi:10.1016/j.lfs.2005.12.047. PMID 16458328.
- Park, Young-Mi; Won, Jong-Heon; Kim, Yang-Hee; Choi, Jong-Won; Park, Hee-Juhn; Lee, Kyung-Tae (2005). "In vivo and in vitro anti-inflammatory and anti-nociceptive effects of the methanol extract of Inonotus obliquus". Journal of Ethnopharmacology 101 (1–3): 120–8. doi:10.1016/j.jep.2005.04.003. PMID 15905055.
- Mishra, Siddhartha Kumar; Kang, Ju-Hee; Kim, Dong-Kyu; Oh, Seung Hyun; Kim, Mi Kyung (2012). "Orally administered aqueous extract of Inonotus obliquus ameliorates acute inflammation in dextran sulfate sodium (DSS)-induced colitis in mice". Journal of Ethnopharmacology 143 (2): 524–32. doi:10.1016/j.jep.2012.07.008. PMID 22819687.
- Zheng, W. F.; Liu, T.; Xiang, X. Y.; Gu, Q. (July 2007). "Sterol composition in field-grown and cultured mycelia of Inonotus obliquus". Yao xue xue bao = Acta pharmaceutica Sinica 42 (7): 750–756. PMID 17882960.
- Zheng W, Miao K, Liu Y, Zhao Y, Zhang M, Pan S et al. (2010). "Chemical diversity of biologically active metabolites in the sclerotia of Inonotus obliquus and submerged culture strategies for up-regulating their production". Appl Microbiol Biotechnol 87 (4): 1237–54. doi:10.1007/s00253-010-2682-4. PMID 20532760.
- Zheng, W. F. (July 2008). "Phenolic compounds from Inonotus obliquus and their immune-stimulating effects". Mycosystema 27 (4): 574–581.
- Müllauer, Franziska (2011). "Betulinic Acid Induced Tumor Killing".
- Paper with background on extraction processes
- Rhee, S.Y. (2008). "A comparative study of analytical methods for alkali-soluble β-glucan in medicinal mushroom, Chaga (Inonotus obliquus)". LWT - Food Science and Technology 41 (3): 545–549. doi:10.1016/j.lwt.2007.03.028.
- Smith JE, Rowan NJ, Sullivan R [ Medicinal Mushrooms: Their Therapeutic Properties and Current Medical Usage with Special Emphasis on Cancer Treatments], 2001
- Cristina Lull, Harry J. Wichers, and Huub F. J. Savelkoul [ "Antiinflammatory and Immunomodulating Properties of Fungal Metabolites"], Wageningen University and Research Center, The Netherlands 2005
- Hobbs, Christopher (1986) Medicinal Mushrooms: An Exploration of Tradition, Healing, & Culture, Summertown, TN, Book Publishing Company, pp. 121–124, ISBN 1-57067-143-5
- Ulrike Lindequist, Timo H. J. Niedermeyer, and Wolf-Dieter Jülich [" The Pharmacological Potential of Mushrooms"], Oxford University Press 2005
- Andrea T. Borchers, Anita Krishnamurthy, Carl L. Keen, Frederick J. Meyersà, and M. Eric Gershwin ["Immunobiology of Mushrooms"], Society for Experimental Biology and Medicine 2008