''Inonotus obliquus'', commonly called chaga (a Latinisation of the Russian word ''чага''), is a fungus in the family Hymenochaetaceae. It is parasitic on birch and other trees. The sterile conk is irregularly formed and resembles burnt charcoal. It is not the fruiting body of the fungus, but a sclerotium or mass of mycelium, mostly black because of a great amount of melanin. Some people consider chaga medicinal. ''Inonotus obliquus'' is found most commonly in the Circumboreal Region of the Northern Hemisphere, where it is distributed in birch forests.

Common names

The name ''chaga'' () comes from the Russian name of the fungus, russian: чага, translit=čaga, label=none, which in turn is borrowed from the word for "mushroom" in Komi, kv, тшак, translit=tšak, label=none, the language of the indigenous peoples in the Kama River Basin, west of the Ural Mountains. It is also known as the

clinker Clinker may refer to: *Clinker (boat building), construction method for wooden boats *Clinker (waste), waste from industrial processes *Clinker (cement), a kilned then quenched cement product * ''Clinkers'' (album), a 1978 album by saxophonist St ...

polypore, cinder conk, black mass and birch canker polypore. In England and officially in Canada, it is known as the sterile conk trunk rot of birch.

Morphology

''Inonotus obliquus'' causes a white heart rot to develop in the host tree. The chaga spores enter the tree through wounds, particularly poorly healed branch stubs. The white rot decay will spread throughout the heartwood of the host. During the infection cycle, penetration of the

sapwood Wood is a porous and fibrous structural tissue found in the stems and roots of trees and other woody plants. It is an organic materiala natural composite of cellulose fibers that are strong in tension and embedded in a matrix of lignin t ...

occurs only around the sterile exterior mycelium mass. The chaga fungus will continue to cause decay within the living tree for 10–80+ years. While the tree is alive, only sterile mycelial masses are produced (the black exterior conk). The sexual stage begins after the tree, or some portion of the tree, is killed by the infection. ''I. obliquus'' will begin to produce fertile fruiting bodies underneath the bark. These bodies begin as a whitish mass that turn to brown with time. Since the sexual stage occurs almost entirely under the bark, the fruiting body is rarely seen. These fruiting bodies produce basidiospores which will spread the infection to other vulnerable trees.

Distribution and cultivation

Generally found growing on birch ('' Betula'' spp.) trees, it has also been found on alder ('' Alnus'' spp.), beech ('' Fagus'' spp.) and poplar (''

Populus ''Populus'' is a genus of 25–30 species of deciduous flowering plants in the family Salicaceae, native to most of the Northern Hemisphere. English names variously applied to different species include poplar (), aspen, and cottonwood. The we ...

'' spp.). In species other than birch, the fungus often appears as buried stem canker, instead of the charcoal-like mass found on birch trees. Attempts at cultivating this fungus on potato dextrose agar and other simulated mediums resulted in a reduced and markedly different production of metabolites. Cultivated chaga developed a reduced number of phytosterols, particularly lanosterol, an intermediate in the synthesis of

ergosterol Ergosterol (ergosta-5,7,22-trien-3β-ol) is a sterol found in cell membranes of fungi and protozoa, serving many of the same functions that cholesterol serves in animal cells. Because many fungi and protozoa cannot survive without ergosterol, the ...

and lanostane-type triterpenes.

Chemistry

The black sclerotium has large concentrations of melanin. Chaga contains extremely high concentrations of oxalate, 2800–11200 mg total oxalates/100 g sclerotium, one of the highest reported in any organism.

Preparation

Chaga is traditionally grated into a fine powder and used to brew a beverage resembling coffee or tea and tastes strongly of

Chinese herbal tea Lingnan culture, or Cantonese culture, refers to the regional Chinese culture of the region of Lingnan: twin provinces of Guangdong and Guangxi, the names of which mean "eastern expanse" and "western expanse" respectively. Strictly speaking, ...

. However, caution is warranted with chronic use due to the extremely high concentrations of oxalates in chaga. Three extraction processes may be used. * Hot water extraction is certainly the most common preparation. A decoction is created by simmering, blocklike pieces of the chaga in numerous quarts of water until the water is reduced and the remaining liquid contains a portion of the chaga's concentrated water-soluble compounds. Such preparations, produced in China and Japan, are exported worldwide. The ß-D-glucans may have a content of approximately 35% in a pure extract. If chaga tea is prepared at home, the chaga chunks can be reused multiple times. * Ethanol or

methanol Methanol (also called methyl alcohol and wood spirit, amongst other names) is an organic chemical and the simplest aliphatic alcohol, with the formula C H3 O H (a methyl group linked to a hydroxyl group, often abbreviated as MeOH). It is a ...

extraction isolates the water-insoluble components,

betulinic acid Betulinic acid is a naturally occurring pentacyclic triterpenoid which has antiretroviral, antimalarial, and anti-inflammatory properties, as well as a more recently discovered potential as an anticancer agent, by inhibition of topoisomerase. I ...

betulin Betulin is an abundant, naturally occurring triterpene. It is commonly isolated from the bark of birch trees. It forms up to 30% of the dry weight of silver birch bark. It is also found in birch sap. '' Inonotus obliquus'' and red alder also co ...

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 Chitin ( C8 H13 O5 N)n ( ) is a long-chain polymer of ''N''-acetylglucosamine, an amide derivative of glucose. Chitin is probably the second most abundant polysaccharide in nature (behind only cellulose); an estimated 1 billion tons of chit ...

effectively—heat is essential. *

Fermentation Fermentation is a metabolic process that produces chemical changes in organic substrates through the action of enzymes. In biochemistry, it is narrowly defined as the extraction of energy from carbohydrates in the absence of oxygen. In food ...

is the most time-consuming and most expensive. Because fermentation methods are not standardized (many types of bacteria and fungi can be used in the process), the outcome is also not standardized.

References