β -amyrin heptadecanoate, a new oleanane triterpenoid with α -glucosidase inhibitory and cytotoxic activities from the leaves of Averrhoa bilimbi L.

A previously unreported oleanane triterpenoid, β-amyrin heptadecanoate (1), was isolated from the leaves of Thai Averrhoa bilimbi (Oxalidaceae), along with five known compounds, β-amyrin (2), β-sitosterol (3), β-sitosterol-D-glucoside (4), β-sitosteryl oleate (5), and α-tocopherol (6). Their structures were elucidated through spectroscopic analysis, including extensive NMR and HRESIMS, and by comparison with the previous literature. All isolated compounds were evaluated for their α-glucosidase inhibitory and cytotoxic activities. Compound 6 exhibited the highest α-glucosidase inhibition (IC50 of 0.72 ± 1.02 µM), significantly outperforming the standard acarbose (IC50 of 82.00 ± 0.24 μM). Furthermore, compound 4 demonstrated the most potent cytotoxicity against HeLa cells (IC50 of 34.92 ± 0.45 μM), while compound 3 exhibited the strongest cytotoxicity towards A549 cells (IC50 of 9.17 ± 0.30 μM). Additionally, a molecular docking study was conducted on the active α-glucosidase inhibitors to estimate their binding affinities and to identify the ligand-binding sites within the enzyme.