Cyathane diterpenoids and drimane sesquiterpenoids with neurotrophic activity from cultures of the fungus Cyathus africanus.

Five terpenoids, including two new cyathane diterpenoids neocyathin S (1) and neocyathin T (2), together with three drimane sesquiterpenoids, one known 3ß,6ß-dihydroxycinnamolide (3), two new ones 3ß,6α-dihydroxycinnamolide (4) and 2-keto-3ß,6ß-dihydroxycinnamolide (5), were isolated from the cultures of the basidiomycete Cyathus africanus. Their structures were established based on extensive spectroscopic methods including 2D NMR (HSQC, 1H‒1H-COSY, HMBC, ROESY) and HRESIMS experiments. The absolute configurations of two pairs of epimers, 1 and 2 as well as 3 and 4, were determined by ECD quantum chemical calculation. All the five compounds enhanced nerve growth factor (NGF)-mediated neurite outgrowth using rat pheochromocytoma (PC12) cells at concentration 10 µM.

Production of bioactive cyathane diterpenes by a bird's nest fungus Cyathus gansuensis growing on cooked rice.

Cyathane diterpenes are important bioactive substances produced by some edible and medicinal fungi. Seven new cyathane type diterpenes, named as cyathins J-P (1-7), together with two known diterpenes (8 and 9), were isolated from the solid culture of the bird's nest fungus Cyathus gansuensis growing on cooked rice. The structures of the new secondary metabolites were elucidated by NMR experiments. Bioactivity screening indicated that compounds 1, 2, 4, and 8 showed moderate inhibitory activity against NO production in lipopolysaccharide-activated macrophages with an IC50 value of 42, 78, 80, and 16 µM, respectively. The fungus C. gansuensis is a promising source of bioactive secondary metabolites and has application potential in preparing healthy food.