Chemical diversity of biologically active metabolites in the sclerotia of Inonotus obliquus and submerged culture strategies for up-regulating their production
BACKGROUND To investigate the antitumor effect of Inonotus obliquus Pilat, the antiproliferative effect of lanostane triterpenoids from a chloroform extract of I. obliquus sclerotia against mouse leukemia P388 cells was assessed. MATERIALS AND METHODS Cell viability was measured by MTT assay. Caspase-3/7 activity and DNA fragmentation were evaluated to analyze apoptosis induction. The in vivo antitumor effect was evaluated by the number of survival days of mouse leukemia P388-bearing female CDF1 mice. RESULTS The chloroform extract of I. obliquus sclerotia inhibited proliferation of the P388 cells. Among the triterpenoids examined, only inotodiol inhibited P388 cell proliferation. DNA fragmentation and caspase-3/7 activation were observed in the P388 cells treated with inotodiol (30 microM). A caspase-3 inhibitor, DEVD-CHO (N-acetyl-Asp-Glu-Val-Asp-al, 100 microM) partially inhibited the DNA fragmentation and growth-inhibition induced by inotodiol. The intraperitoneal administration of 10 mg/kg inotodiol prolonged the number of survival days of the P388-bearing mice. CONCLUSION Inotodiol inhibits cell proliferation through apoptosis induction by activating caspase-3.