Cardiovascular Effects of 3-Methylquercetin

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Abstract
We have investigated the pharmacological effects of 3-methylquercetin (3-MQ) on rabbit blood platelets, the rabbit central ear artery, and the guinea pig right and left atria. The results were compared with those obtained with quercetin (Q) and rutin (R). 3-MQ and Q showed an antiaggregating effect which was also seen to a lesser extent for R. The antiaggregatory effect of Q and 3-MQ was only important for a concentration of 1 × 10-4 g/ml (3 × 10-4M), which proved to be toxic for isolated cells. Both 3-MQ and Q inhibited cyclo-oxygenase but their activity was lower in comparison with that of indomethacin. High concentrations of 3-MQ (5 × 10-5 and 1 × 10-4 g/ml; 1.5 and 3 × 10-4M) inhibited lipoxygenase, but again these concentrations were too high to be of therapeutical importance. The vasorelaxation of the rabbit central ear artery was low in comparison with that obtained for papaverin. 3-MQ had a positive chronotropic effect on the guinea pig right atrium in a concentration which was 4 times lower than the 50% cytotoxic dose (1 × 10-5 g/ml; 3 × 10-5M). It had also an anti-arrhythmic effect on the left atrium of the guinea-pig in concentrations of 1 × 10-5 and 2 × 10-5 g/ml (3 and 6 × 10-5M). The positive chronotropic effect could be important when 3-MQ is used in high doses.