A NEW FLAVONE C-GLYCOSIDE AND ANTIPLATELET AND VASORELAXING FLAVONES FROM GENTIANA-ARISANENSIS

A new flavone C-glycoside, isovitexin 6''-O-glucoside (1), and three k nown flavonoids. quercetin, isovitexin, and luteolin-7-O-beta-D-glucos ide, have been further isolated from the whole plant of Gentiana arisa nensis Hayata. The new compound was characterized by spectral methods and chemical reactions. The antiplatelet effects of isovitexin 6''-O-g lucoside (1), isoorientin (2), 2 peracetate (3), isovitexin (4), luteo lin 7-O-beta-D-glucoside (5), luteolin (6), isoorientin 6''-O-glucosid e (7), and 7 peracetate (8) were studied using washed rabbit platelets . Of the compounds tested, 6 showed potent antiplatelet effects on ara chidonic acid (AA)-induced platelet aggregation (IC50 = 43.5 mu M). Th e effect of 2, 5, and 6 on the contraction of rat thoracic aorta was a lso studied. Compound 6 depressed markedly the contraction induced by Ca2+ (1.9 mM) in high-K+ (80 mM) medium, with an IC50 of about 156 mu M and also inhibited noradrenaline (3 mu M)-induced phasic and tonic c ontractions, with an IC50 of about 68 and 72 mu M, respectively.