Bioactive triterpenoids and water-soluble melanin from Inonotus obliquus (Chaga) with immunomodulatory activity
Christian Winther Wold, William H. Gerwick, Helle Wangensteen, Kari Tvete Inngjerdingen
Abstract
The fungus Inonotus obliquus has historically been used in traditional medicine in Europe and Asia. A melanin fraction and six triterpenoids were obtained from I. obliquus sclerotia, and evaluated in various bioassays including for immunomodulatory, cytotoxicity and enzyme-interacting properties. The water-soluble, nitrogen-free melanin fraction and the triterpenoids 3β-hydroxy-8,24-dien-21-al (1) and inotodiol (2) displayed potent activity in a human complement assay. The melanin fraction inhibited the complement cascade, whereas 1 and 2 activated the same cascade. Compound 2, as well as betulinic acid (3) and betulin (4) had anti-proliferative properties against the colon adenocarcinoma cell line HT29-MTX. Further, the melanin fraction and betulin-3-O-caffeate (6) reduced nitric oxide production in primary murine macrophages. Furthermore, the metabolites were nontoxic against the common gut bacteria E. coli and B. subtilis. The results demonstrate the anti-inflammatory and immunomodulatory effects of I. obliquus melanin and triterpenoids, which could potentially justify the consumption of this increasingly popular “edible” fungus.