NOVEL ANTIPLATELET NAPHTHALENE FROM RHAMNUS-NAKAHARAI

A new naphthalene derivative, isotorachrysone [1], was isolated from t he stem bark of Rhamnus nakaharai along with several known compounds. The antiplatelet effects of isotorachrysone [1], isotorachrysone perac etate [2], 6-methoxysorigenin [3], quercetin 3-O-methyl ether [4], and quercetin 3-O-methyl ether peracetate [5] were studied using washed r abbit platelets. Of the compounds rested, 1, 2, 4, and 5 showed potent antiplatelet effects on arachidonic acid (AA-) and collagen-induced p latelet aggregation. Compound 5 also showed potent antiplatelet, effec ts on platelet-activating factor-(PAF-) induced platelet aggregation. Isotorachrysone [1] and its peracetate [2] were also studied for antip latelet activity in human platelet-rich plasma (PRP) and both showed p otent inhibition of the secondary aggregation induced by epinephrine. The antiplatelet effects of 1 and 2 are due partially co an inhibitory effect on thromboxane formation.