Hawaiinolides E-G, cytotoxic cassane and cleistanthane diterpenoids from the entomogenous fungus Paraconiothyrium hawaiiense.

Hawaiinolides E-G (1-3), three additional new secondary metabolites including two cassane (1 and 2) types of diterpene lactones and one cleistanthane (3) diterpenoid, were isolated from the scale-up fermentation extract of Paraconiothyrium hawaiiense, an entomogenous fungus isolated from the Septobasidium-infected insect Diaspidiotus sp. The structures of 1-3 were elucidated by nuclear magnetic resonance experiments, and 1 and 3 were further confirmed by X-ray crystallography. The absolute configurations of 1 and 3 were assigned by single-crystal X-ray diffraction analysis using Cu Kα radiation, whereas that of 2 was deduced via the circular dichroism data. Compound 1 showed significant cytotoxic effects against the human tumor cell line T24, with an IC₅₀ value (9.32 μM) comparable to that of the positive control cisplatin.