The 2,3-epoxy naphthoquinol produced by endophyte M-211.

A novel 2,3-epoxy naphthoquinol, named (6,7,8)-theissenone A (), possessing an oxatricyclo[5.4.0.0]undeca-trien-2-one skeleton, together with two known compounds, (6,7,8)-theissenone () and arthrinone (), were produced by an endophytic fungus, M-211, which was isolated from mangrove plants. The structure of , including the absolute stereochemistry, was elucidated by analysis of nuclear magnetic resonance (NMR) and mass spectrometry (MS) data and time-dependent density functional theory (TDDFT) calculations of electronic circular dichroism (ECD) spectra. Additionally, the absolute structure of was deduced as a diastereomer of using ECD spectral data analysis. Compounds , and exhibited cytotoxic activity against the H4IIE rat hepatoma cells, with IC values of 67.5, 46.6 and 13.4 µM, respectively.