Phenolic compounds from field-grown Inonotus obliquus sclerotia (Chaga) consist mainly of hispidin analogs and melanins, and are thought to be the active constituents to treat several human diseases. In submerged cultures of the fungus, however, no information is currently available on the production of phenolic compounds and their corresponding pharmacological functions. In this study, phenolic compounds from Chaga and submerged cultures of the fungus were assayed for their composition and immune-stimulating effects. Phenolic compounds produced by I. obliquus in submerged cultures mostly consist of flavonoids, together with small amounts of hispidin analogs and melanins. This is quite contrary to the situation in Chaga, where flavonoids are determined as trace elements. Furthermore, phenolic compounds from Chaga show capacity about two-fold higher than those produced in submerged cultures in inhibiting cyclophosphamide-induced reduction of bodyweight, spleen index and viability of peripheral lymphocytes in test mice. Thus less production of hispidin analogs and melanins is likely to be responsible for less immune-stimulating effects in phenolic compounds from submerged cultures, and additional factors should be imposed during submerged cultures of I. obliquus to regulate biosynthesis of phenolic compounds directed to the composition similar to Chaga.
Lanosterol and ergosterol are the active principles with potential pharmacological activities in Inonotus obliquus. However, the two sterols are less accumulated in cultured mycelia of the fungus. In this study, different carbon and nitrogen sources and pH levels together with three metal ions were assayed for their effects on accumulation of the two sterols in the fungus. Among the tested media the growth medium consisting of glucose (1.5%), rice powder (0.5%), yeast extract (0.4%), wheat bran (0.1%), KH2PO4 (0.01%) and MgSO4·7H2O (0.05%) with pH level at 6.5 yielded a maximum production of the two sterols, which can further be increased following the treatment of Ag+, Cu2+ and Ca2+. Supplementing Ag+ at concentrations of 0.28 and 0.35μmol partially inhibited ergosterol biosynthesis, leading to an enhanced accumulation of lanosterol, the presence of intermediates of ergosterol biosynthetic pathway and a reduced accumulation of ergosterol in cultured mycelia of I.
