Antiplatelet activity of some prenylflavonoids.

Eight naturally occurring prenylflavonoids were tested for their antiplatelet activities in rabbit platelet suspension. Cyclomorusin and artomunoxanthone showed strong inhibition of platelet-activating factor (PAF; 1-O-alkyl-2-acetyl-sn-glycero-3-phosphocholine) induced platelet aggregation. Cyclomulberrin, dihydroisocycloartomunin, cyclocommunol and cyclocommunin showed strong inhibition of arachidonic acid (AA)- and collagen-induced platelet aggregation. Cyclomorusin also inhibited markedly collagen-induced platelet aggregation. Cyclocommunin, dihydroisocycloartomunin and cyclomulberrin also showed slight but significant antiplatelet effects on the aggregation induced by PAF. Of the compounds tested, cyclocommunin exhibited the most potent inhibition of platelet aggregation induced by collagen (IC50 = 14.4 microM) and AA (IC50 = 12.5 microM). Thromboxane B2 formation caused by AA was suppressed by cyclocommunin and artomunoxanthone.