Qualitative analysis of secondary metabolites of chaga mushroom ( Inonotus Obliquus): phenolics, fatty acids, and terpenoids

Chaga mushroom is a black perennial fungus that usually parasites on adult birch tree trunks. It has been conventionally used as a health-promoting supplement and nutraceutical in different cultures for centuries. The desired clarification of the profile of chaga secondary metabolites responsible for various bioactive properties has been continuously pursued for decades but has only partially been unveiled. Meanwhile, in recent years, attention to food safety, quality stability, authentication, and sustainability of chaga products from the wild has become increasingly popular in the current commercial market and related small/medium-size food industry enterprises. Phenolic, hydroxylated fatty acid, and terpenoid compounds produced by sclerotia of chaga mushrooms are bioactive constituents with antioxidant, anti-microorganism, and anti-tumor activities. Some new secondary metabolites of chaga mushroom have occasionally been reported previously, and effects of environment (e.g., cultivation method, harvesting region) on compositional characteristics noted. However, these have rarely and systematically compared the compositions of their material with a reliable database of known secondary metabolites of chaga. Therefore, this study aimed to achieve a rapid screening and characterization of secondary metabolites of Newfoundland chaga. A total of 111 phenolic, 63 fatty/aromatic acid, and 108 terpenoid constituents was primarily identified using HPLC-ToF-MS (high-performance liquid chromatograph coupled with time-of-flight mass spectra), among which 161 were newly reported. In addition, an update of the compositional database of chaga was provided as supplementary materials to help utilization and development of Newfoundland chaga mushroom as edible-fungi. Conclusively, chaga mushroom is a very promising food supplement abundant in numerous fungal secondary metabolites that were rarely found in other edible materials, even though its safety (e.g., oxalate content) aspects is still in need of additional investigation for being considered as a viable commercial nutraceutical.