Aspergiloid I, an unprecedented spirolactone norditerpenoid from the plant-derived endophytic fungus Aspergillus sp. YXf3

An unusual C(18) norditerpenoid, aspergiloid I (1), was isolated from the culture broth of Aspergillus sp. YXf3, an endophytic fungus derived from Ginkgo biloba. Its structure was unambiguously established by analysis of HRMS–ESI and spectroscopic data, and the absolute configuration was determined by low-temperature (100 K) single crystal X-ray diffraction with Cu Kα radiation. This compound is structurally characterized by a new carbon skeleton with an unprecedented 6/5/6 tricyclic ring system bearing an α,β-unsaturated spirolactone moiety in ring B, and represents a new subclass of norditerpenoid, the skeleton of which is named aspergilane. The hypothetical biosynthetic pathway for 1 was also proposed. The cytotoxic, antimicrobial, anti-oxidant and enzyme inhibitory activities of 1 were evaluated.