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

A new stereoisomer coumarin, melichumarin A (1), together with 16 known biogenetically related analogues (2-17), was separated and characterised from the above-ground parts of Melicope chunii. The molecular structure of 1 was elucidated through a comprehensive array of spectroscopic techniques, and the spectral data of the known analogues (2-17) were compared with those reported in the literature. Preliminary pharmacological evaluations were performed on all the isolated compounds. The findings indicated that compounds 1-17 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 μM.