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.