Sixteen constituents from Formosan Moraceous plants were tested for their antiplatelet activities in rabbit platelet suspension and human platelet-rich plasma. Cycloartocarpin A, cycloheterophyllin, broussochalcone A, kazinol A, broussoaurone A, and broussoflavonol F showed strong inhibition of arachidonic acid (AA)-induced platelet aggregation. Of the compounds tested, broussochalcone A exhibited the most potent inhibition of platelet aggregation induced by AA (IC50 = 6.8 microM). The antiplatelet effects of cycloheterophyllin, broussochalcone A, kazinol B, broussoaurone A, and broussoflavonol F are partially due to an inhibitory effect on cyclooxygenase.
Two new arylnaphthalide lignans, procumphthalide A (1) and 4-O-beta-D-glucopyranosyl-(1"'-->2")-beta-D-apiofuranosyldiphyllin, named procumbenoside B (2), along with cilinaphthalide B (3) and several other known compounds were isolated from the methanolic extracts of Justicia procumbens. By using NMR and other spectral methods, the structures of 1 and 2 were elucidated. Cilinaphthalide B (3), justicidin A (4), and taiwan E methyl ether (5) were shown to have an antiplatelet effect in human plateletrich plasma. In human citrated PRP, 5 showed a strong inhibitory effect on platelet aggregation induced by adrenaline in a concentration-dependent manner, with an IC(50) value of about 27.6 microM.
A new naphthalene derivative, isotorachrysone [1], was isolated from the stem bark of Rhamnus nakaharai along with several known compounds. The antiplatelet effects of isotorachrysone [1], isotorachrysone peracetate [2], 6-methoxysorigenin [3], quercetin 3-O-methyl ether [4], and quercetin 3-O-methyl ether peracetate [5] were studied using washed rabbit platelets. Of the compounds tested, 1, 2, 4, and 5 showed potent antiplatelet effects on arachidonic acid (AA-) and collagen-induced platelet aggregation. Compound 5 also showed potent antiplatelet effects on platelet-activating factor-(PAF-) induced platelet aggregation. Isotorachrysone [1] and its peracetate [2] were also studied for antiplatelet activity in human platelet-rich plasma (PRP) and both showed potent inhibition of the secondary aggregation induced by epinephrine. The antiplatelet effects of 1 and 2 are due partially to an inhibitory effect on thromboxane formation.
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