Annoglabrin A-C, three new ent-kaurane diterpenoids from the Annona glabra fruit pulp

Three new ent-kaurane diterpenoids, namely annoglabrin A-C (1-3), were isolated from the Annona glabra fruit pulp. Their structures were clarified by widespread spectroscopic analyses (1D and 2D NMR, HRESIMS). The relative configuration of these new compounds was established through the NOESY spectrum. Compounds 1-3 were evaluated for their inhibitory activity against alpha-glucosidase and were found with weak (1 and 3) or no effects (2), compared to those of positive control (acarbose, IC50 82.0 mu M).