Cyathane diterpenes from Chinese mushroom Sarcodon scabrosus and their neurite outgrowth-promoting activity

Two novel cyathane diterpenoids, designated scabronines K (1) and L (2), were isolated from the fruiting bodies of the basidiomycete Sarcodon scabrosus together with four known analogues, sarcodonins G (3), A (5), M (6), and scabronine H (4). Their structures were elucidated on the basis of extensive spectroscopic analysis including 2D-NMR (HMBC, HSQC, ROESY, (1)H,(1)H-COSY) and MS experiments. The isolated compounds were evaluated for nerve growth factor (NGF)-mediated neurite outgrowth using rat pheochromocytoma (PC12) cells as a model system of neuronal differentiation. Among these compounds, only sarcodonins G and A (3 and 5) at 25 μM showed significant neurite outgrowth (neuritegenesis)-promoting activity in the presence of 20 ng/mL NGF after 24h treatment. Their structure-neurite inducing activity relationship was also discussed.