Bioactive triterpenoids and water-soluble melanin from Inonotus obliquus (Chaga) with immunomodulatory activity

•A water-soluble I. obliquus melanin inhibited the human complement cascade.•The melanin fraction was nontoxic against bacteria commonly found in the human gut.•The triterpenoid 3β-hydroxy-8,24-dien-21-al activated the human complement cascade.•Several triterpenoids were highly active against colon carcinoma cell line HT29-MTX.