Isochaetomium A2, a new bis(naphthodihydropyran-4-one) with antimicrobial and immunological activities from fungus Chaetomium microcephalum.

Isochaetomium A2 (1), a new bis(naphthodihydropyran-4-one), along with chaetochromins A (2) and B (3), was isolated from the solid-state fermented rice culture of Chaetomium microcephalum. The structure of compound 1 was elucidated on the basis of 1D and 2D NMR spectral data, and the relative configuration was confirmed by CD spectrum. Compounds 1-3 possessed significant antimicrobial activity against Escherichia coli 1.044, Staphylococcus aureus 1.252, and Bacillus subtilis 1.079. Moreover, compounds 1-3 showed obvious inhibitory effects on mouse spleen cell proliferation with successive IC50 values of 0.52, 0.19, and 0.24 μM.