Antiplatelet aggregation coumarins from the leaves of Murraya omphalocarpa.

Using a bioactivity-guided fractionation method, two coumarins: minumicroline acetonide (1) and epimurpaniculol senecioate (2), were isolated from the leaves of Murraya omphalocarpa Hayata (Rutaceae). Compound 1 had been previously synthesized and was now isolated from natural sources for the first time, and compound 2, possessing a negative optical rotation value, is new. The structures and their stereochemistry were fully elucidated on the basis of spectroscopic and X-ray crystallographic techniques. Both compounds 1 and 2 are active in the antiplatelet aggregation assay. Interestingly, the possible acetonide artifact 1 displayed significant antiplatelet aggregation induced not only by AA and collagen but also by platelet activating factor (PAF).

Cytotoxic principles from the formosan milkweed, Asclepias curassavica.

A series of cardenolides and related compounds have been isolated from the aerial parts and roots of the ornamental milkweed, Asclepias curassavica. Their structures were determined by spectroscopic and chemical methods. Among them, three derivatives of calactinic acid methyl ester (13-15), 19-nor-16 alpha-acetoxy-10 beta-hydroxyasclepin (16), 20 beta,21-dihydroxypregna-4,6-dien-3-one (19), and 3,4-seco-urs-20(30)-en-3-oic acid (22) are new compounds. The relative configuration of calactinic acid methyl ester (12) has been confirmed by X-ray diffraction analysis on its derivative 13. Most of the cardenolides obtained showed pronounced cytotoxicity against four cancer cell lines (IC(50) 0.01 to 2.0 microg/mL).