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.

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