Chronotropic, Inotropic, and Lusitropic Effects of Flavonoids

We summarized the recent findings on the acute myocardial effects of several flavonoids, whose long-term beneficial effects through antioxidant activity has attracted attention. Polymethoxyflavones, such as sudachitin, demethoxysudachitin, and nobiletin, showed chronotropic and inotropic effects; the effects were milder than those of β-adrenoceptor agonists. Their strength of action appeared to be related to the number of methoxy groups in the chemical structure. Sudachitin also showed strong vasorelaxant effect causing full relaxation. Quercetin showed positive lusitropic effects in both normal and diabetic myocardium; this was probably mediated by enhancement of Ca²⁺ sequestration into the sarcoplasmic reticulum by the Ca²⁺ ATPase. Hesperetin inhibited the spontaneous firing of action potential in the pulmonary vein myocardium; the chronotropic inotropic and lusitropic effects were weak or not observed. Thus, each flavonoid compound has characteristic pharmacological effects probably through their action on specific cellular targets. Further investigation of their effects would provide insights for the development of therapeutic agents for heart diseases such as heart failure and arrhythmia.