Bioactive coumarins from the leaves of Murraya omphalocarpa.

Using antiplatelet aggregation as a guide to fractionation, eight coumarins, omphalocarpinol (1), 5,7-dimethoxy-8-(3'-methyl-2'-oxobutyl)coumarin (2), murralongin, murrayanone, omphamurin (5), murragleinin, mexoticin, and murrangatin, were isolated from the leaves of Murraya omphalocarpa. Compound 1 is new, and 5 is a new enantiomer of omphamurin. The structures of these compounds were elucidated on the basis of spectroscopic techniques, and the structure of compound 1 was confirmed by X-ray crystallographic analysis. Among them, compounds 1, 2 and 5 exhibited significant antiplatelet aggregation activity.