In vivo and in vitro animal investigation of the effect of a mixture of herbal extracts from Tribulus terrestris and Cornus officinalis on penile erection

Abstract

Introduction: Herbal preparations have long been used as folk remedies for erectile dysfunction (ED).

Aim: This study examined the effects of Tribulus terrestris and Cornus officinalis extracts on relaxation of the smooth muscle of the corpus cavernosum (CC), their mechanisms of action, and the effects of oral administration of a mixture of the herbal extracts on penile erection.

Methods: The relaxation effects and the mechanisms of action of T. terrestris extract, C. officinalis extract, and the mixture of both extracts on the rabbit CC were investigated in an organ bath. To evaluate whether the relaxation response of the CC shown in an organ bath occurs in vivo, intracavernous pressure (ICP) was calculated in rats after oral administration for a month. Additionally, adenosine 3',5'-cyclic monophosphate (cAMP) and guanosine 3', 5'-cyclic monophosphate (cGMP) in the CC were measured using immunoassay.

Main outcome measures: Smooth muscle relaxation was expressed as the percent decrease in precontraction induced by phenylephrine. ICP was assessed in rats after the oral administration of a mixture of both extracts for 1 month and changes in cGMP and cAMP concentrations were measured based on the concentration of the mixture of both extracts.

Results: T. terrestris extract, C. officinalis extract, and the mixture of both extracts showed concentration-dependent relaxation effects of the CC. In both the endothelium-removed group and N(G)-nitro-L-arginine methyl ester pretreatment group, T. terrestris extract inhibited relaxation. ICP measured after oral administration of the extract mixture for a month was higher than that measured in the control group, and a significant increase in cAMP was observed in the mixture group.

Conclusions: T. terrestris extract and C. officinalis extract exhibited concentration-dependent relaxation in an organ bath. In the in vivo study of the extract mixture, ICP and cAMP was significantly potentiated. Accordingly, the mixture of T. terrestris extract and C. officinalis extract may improve erectile function.