An antiplatelet aggregation principle and X-ray structural analysis of cis-khellactone diester from Peucedanum japonicum.

Three structurally related khellactone coumarins, 1-3, were isolated from the aerial parts of Peucedanum japonicum (Umbelliferae). Compound 2 was identified as a new coumarin (cis-3'-isovaleryl-4'-senecioylkhellactone) by spectral and chemical analysis. Conformation of the dihydropyrano ring of cis-3',4'-disenecioylkhellactone [3] was elucidated by X-ray crystallographic analysis. These three natural khellactone esters were subjected to the antiplatelet aggregation bioassay where cis-3',4'-diisovalerylkhellactone [1] showed significant activity (at 50 micrograms/ml).