Benzophenone and chromone derivatives and their dimers from the scale-insect pathogenic fungus Orbiocrella petchii BCC 51377

A benzophenone derivative, orbiophenone A, and its homodimer, orbiocrellone A, a chromone derivative, orbiochromone A, four benzophenone–chromone heterodimers, orbiocrellones B–E, and a benzophenone–tetrahydroxanthone dimer, ent-secalonic acid I, were isolated from cultures of the scale-insect pathogenic fungus Orbiocrella petchii BCC 51377. Their structures were elucidated by spectroscopic analyses and chemical correlations. Orbiochromone A was isolated for the first time as an optically active natural product, and its absolute configuration was determined by the ECD spectrum combined with TD-DFT calculations. Four of the dimeric compounds, orbiocrellones B–D and ent-secalonic acid I, exhibited antimalarial activity against Plasmodium falciparum K1 with IC50 values of 5.7, 5.6, 14, and 5.5 μM, respectively.