A new nemoralisin-type diterpenoid from <i>Aglaia lawii</i>

A new nemoralisin-type diterpenoid, nemoralisin O (<b>1</b>), along with ten previously identified compounds, was obtained from <i>Aglaia lawii</i> bark. Structural characterisation was performed using various spectroscopic techniques, with a focus on 1D and 2D NMR, and HR-ESI-MS analysis. The absolute stereochemistry of compound <b>1</b> was established by comparing its experimental ECD spectrum with theoretical ECD spectra of all eight possible stereoisomers using TD-DFT calculations, and by evaluating compatibility of calculated ¹H chemical shifts with experimental values using DP4 probability method. The cytotoxic effects of some isolated compounds on HepG2 human liver cancer cells and the inhibition of α-glucosidase were evaluated. Compounds <b>4</b>, <b>5</b>, and <b>6</b> exhibited weak cytotoxicity against HepG2 cells, and showed no inhibitory activity against α-glucosidase (IC₅₀ &gt; 256 µg/ml).