Antiplatelet and Anti-Inflammatory Constituents and New Oxygenated Xanthones from Hypericum geminiflorum

Abstract

Two new pentaoxygenated xanthones, 2,3-dihydroxy-1,6,7-trimethoxyxanthone (1) and 3,6-dihydroxy-1,5,7-trimethoxyxanthone (2) were isolated from the leaf of Hypericum geminiflorum. The antiplatelet activities of the constituents, 2,6-dimethoxy-p-benzoquinone (3), gemichalcone A (4), gemichalcone B (5), and cycloartocarpin (6), of this plant, were assessed in vitro by determining their inhibitory effects on the aggregation of washed rabbit platelets induced by various inducers. The anti-inflammatory effects of 4 and 5 were assessed in vitro by determining their inhibitory effects on the chemical mediators released from mast cells and neutrophils. Of the compounds tested, 4 exhibited the most potent inhibition of platelet aggregation induced by arachidonic acid (AA) and 4 and 5 strongly inhibited the release of β-glucuronidase and lysozyme in formyl-Met-Leu-Phe (fMLP)-stimulated rat neutrophils.

Key words

Hypericum geminiflorum - Clusiaceae - pentaoxygenated xanthone - antiplatelet - anti-inflammatory

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