Exolide A, structurally diverse Ent-18-norbeyerane diterpenoid from the stems of Indian mangrove plant, Excoecaria agallocha Linn.

Exolide A (1), a novel ent-18-norbeyerane diterpenoid possessing a hexacarbocyclic framework, 7/5/6/6/5/3 along with four known terpenoids (2-5) were isolated from the chloroform extract of the stems of Excoecaria agallocha. The structure of 1 was elucidated by comprehensive spectroscopic data analysis (IR, HRESIMS, 1H, 13C NMR, DEPT, HSQC, HMBC, 1H-1H COSY, 1H-1H NOESY), chemical methods, and biogenetic considerations. Compound 2 exhibited a potent α-glucosidase inhibitory activity (IC50 0.11 μg/mL) compared to acarbose (IC50 1.44 μg/mL).