Modulatory effects of Aqueous extract from Tetracarpidium conophorum leaves on key enzymes linked to erectile dysfunction and oxidative stress-induced lipid peroxidation in penile and testicular tissues

Tetracarpidium conophorum (walnut) is used in folk medicine for the treatment of erectile dysfunction but the mechanism remains unclear. This study evaluated the effect of aqueous extract from T. conophorum leaves on oxidative stress-induced penile damage and key enzymes linked to erectile dysfunction. The inhibitory effect of the extract on sodium nitroprusside (SNP)-induced lipid peroxidation, arginase, angiotensin I-converting enzyme (ACE) and acetylcholinesterase (AChE) activities in penile and testicular tissue homogenates were determined via colorimetric method. The aqueous extract inhibited SNP-induced lipid peroxidation in rats penile and testicular homogenates in a dose dependent manner. The highest inhibitory effect was obtained in the penis at a concentration of 0.5 mg/mL. Furthermore, the extract inhibited arginase activity in a dose dependent pattern. The IC50 revealed that the extract had significantly (P<0.05) higher inhibitory activity in the penile tissue (130.96 µg/mL) than the testicular tissue (179.02 µg/mL) homogenate. However, the AChE inhibitory activity of the extract was significantly (P<0.05) higher in the testes (0.47 mg/mL) when compared to the penis (0.58 mg/mL). Similarly, the activity of ACE was reduced by the extract. A higher inhibitory activity was observed in the testes (114.21 µg/mL) than the penis (127.71 µg/mL). The observed inhibitory activities could be linked with the phenolic compounds present in the extract and this could further justify the use of T. conophorum leaves for the treatment of ED.