Platelet aggregation inhibitors in hot water extract of green tea.
The effect of hot water extract of green tea on the collagen-induced aggregation of washed rabbit platelets was examined. The extract lowered submaximal aggregation and prolonged the lag time in a dose-dependent manner. After fractionation of the extract, it was revealed that the tea catechins (tannins) are active principles for inhibition and that ester-type catechins are more effective than free-type catechins. One of the ester type catechins, epigallocatechin gallate (EGCG), suppressed the collagen-induced platelet aggregation completely at the concentration of 0.2 mg/ml (= 0.45 mM). Comparing IC50 values of EGCG and aspirin it was found that the potency of EGCG is comparable to that of aspirin. Thrombin- and platelet activating factor (PAF)-induced aggregation was also inhibited by EGCG. The elevation of cyclic adenosine 3',5'-monophosphate (cAMP) level was not observed in EGCG treated platelets.
Sagesaka-Mitane
Y
Y
Ito-en Central Research Institute, Shizuoka, Japan.
Miwa
M
M
Okada
S
S
D000818:Animals; D002392:Catechin / Q000031:analogs & derivatives*; D005419:Flavonoids / Q000302:isolation & purification / Q000494:pharmacology; D066298:In Vitro Techniques; D008297:Male; D010936:Plant Extracts / Q000494:pharmacology*; D010975:Platelet Aggregation Inhibitors; D011817:Rabbits; D013662:Tea / Q000032:analysis*
D005419:Flavonoids; D010936:Plant Extracts; D010975:Platelet Aggregation Inhibitors; D013662:Tea; D002392:Catechin; C057580:gallocatechol