Vasoactive properties of procyanidins from Hypericum perforatum L. in isolated porcine coronary arteries.

Procanidin fractions (PC) were isolated from Hypericum perforatum L. (Guttiferae). Characterization of the main components of each fraction was performed by UV- and mass spectroscopy. Their biological activity was tested in porcine isolated coronary arteries. All PC fractions antagonized histamine- or prostaglandin F2 alpha-induced arterial contractions. In contrast, vasorelaxation was insignificant in KCl-precontracted coronary arteries except with the higher oligomeric PC fraction 3. Vasoactive properties of the PC seem to be dependent on their relative molecular mass. An inhibition of cellular phosphodiesterase might be involved in the underlying mechanism of action.