The leaf extract of Ribes nigrum L. is a potent stimulator of the endothelial formation of NO in cultured endothelial cells and porcine coronary artery rings

BACKGROUND: Endothelial dysfunction is a major hallmark of most types of cardiovascular diseases. Numerous plant extracts have been shown to cause endothelium-dependent relaxations by increasing the endothelial formation of the potent vasoprotective factor, nitric oxide (NO).
OBJECTIVE: The ability of different Ribes nigrum L. extracts (Grossulariaceae) to induce endothelium-dependent relaxation by stimulating the endothelial formation of NO was assesssed.
METHODS: Ribes nigrum extracts were prepared from buds, berries and leaves by extraction (Acetone:H2O:Acetic Acid; 70/28/2 (v/v/v)) and lyophilized after acetone evaporation. The ability of the extracts to stimulate the endothelial formation of NO was assessed using cultured endothelial cells and isolated porcine coronary artery rings.
RESULTS: The Ribes nigrum leaf extract increased to a greater extent than the bud and the berry extracts the formation of NO, and up-regulated eNOS mRNA expression in cultured endothelial cells (the stimulatory effects amounted to 197 ± 9 %, 134 ± 6 % and 118 ± 5 %, respectively). The leaf extract induced greater relaxations of isolated coronary arteries with endothelium than the bud and the berry extracts whereas no such effects were observed in rings without endothelium. Relaxations to the leaf extract were minimally affected by indomethacin and by inhibitors of endothelium-dependent hyperpolarization response, and markedly reduced by NG-nitro-L-arginine.
CONCLUSIONS: The present findings indicate that the Ribes nigrum leaf extract is a more potent inducer of the endothelial formation of NO than the bud and the berry extracts.