Melichumarin A, a new coumarin with nitric oxide inhibitory activity from the stems of <i>Melicope chunii</i>

A new stereoisomer coumarin, melichumarin A (<b>1</b>), together with 16 known biogenetically related analogues (<b>2</b>-<b>17</b>), was separated and characterised from the above-ground parts of <i>Melicope chunii</i>. The molecular structure of <b>1</b> was elucidated through a comprehensive array of spectroscopic techniques, and the spectral data of the known analogues (<b>2</b>-<b>17</b>) were compared with those reported in the literature. Preliminary pharmacological evaluations were performed on all the isolated compounds. The findings indicated that compounds <b>1</b>-<b>17</b> exhibited significant inhibition of NO production in lipopolysaccharide activated in mouse macrophage RAW264.7 cells, with IC₅₀ values between 2.03 ± 0.05 and 15.84 ± 0.08 <i>μ</i>M.