EFFECTS OF FLAVONOIDS FROM LICORICE ROOTS (GLYCYRRHIZA-INFLATA BAT) ON ARACHIDONIC-ACID METABOLISM AND AGGREGATION IN HUMAN PLATELETS

The effects of six flavonoids isolated from Sinkiang Licorice roots (lichochalcones A and B, isoliquiritigenin, isoliquiritin, liquiritigenin and liquiritin) on arachidonate metabolism and aggregation in human platelets were studied. Licochalcones A and B at concentrations of 10(-5) m to 10(-3) m inhibited the formation of 12-hydroxy-5,8,10-heptadecatrienoic acid (HHT) and thromboxane B2 (TXB2), does-dependently. Furthermore, isoliquiritigenin and liquiritigenin at higher concentrations (10(-4) m-10(-3) m) inhibited the formation of HHT and TXB2, while they increased the formation of 12-hydroxy-5,8,10,14-eicosatetraenoic acid (12-HETE). However, isoliquiritin and liquiritin had no effect on arachidonate metabolism. Licochalcones A and B inhibited thrombin-induced platelet aggregation at concentrations of 2 x 10(-5) m to 2 x 10(-4) M. Isoliquiritigenin, liquiritigenin, isoliquiritin and liquiritin had no effects on the thrombin-induced aggregation. To clarify the inhibitory effects of flavonoids in licorice roots on the formation of HHT and TXB2 and thrombin-induced aggregation, we studied the effects of flavonoids on cytosolic free calcium concentrations ([Ca2+]i) induced by thrombin. The results showed that licochalcones A and B inhibited the elevation of [Ca2+]i induced by thrombin, dose-dependently.