Abstract

A phytochemical investigation of the roots of Premna herbacea Roxb. led to the isolation and characterization of ten abietane-type diterpenoids, including five previously undescribed compounds: premnaherbietones A and B ( 1 and 4 ), and premnaherbietanes A–C ( 5 – 7 ). Structural elucidation was achieved using comprehensive spectroscopic analysis (1D and 2D NMR, HRESIMS) and confirmed by electronic circular dichroism (ECD) calculations. The previously undescribed compounds possess diverse carbon skeletons, including quinonemethide abietane, 20(10 → 5)- abeo -abietane, and seco -4,5-abietane frameworks. Selected compounds ( 2 , 3 , 9 , and 10 ) were evaluated for their α -glucosidase inhibitory and cytotoxic activities. Salvilenone ( 10 ) exhibited α -glucosidase inhibition with an IC<inf>50</inf> value of 34.6 μM, significantly outperforming the positive control, acarbose (IC<inf>50</inf> = 190.4 μM). In silico molecular docking revealed that compound 10 interacts with key active site residues of α -glucosidase through hydrogen bonding and π–π interactions, supporting its inhibitory potential. Bharangin ( 2 ) demonstrated notable cytotoxicity against A549 human lung adenocarcinoma cell lines with an IC<inf>50</inf> value of 19.4 μM. A plausible biosynthetic pathway for the isolated diterpenoids is also proposed.