Abstract:
Tropical pumpkin seeds have been employed in folklore for the management of erectile dysfunction (ED) but with little or no biochemical basis for their usage. Hence, this study sought to investigate the effect of some tropical pumpkin seeds (white melon, fluted pumpkin and kalabari) on some key enzymes (phosphodiesterase 5 (PDE-5), arginase, angiotensin-I converting enzyme (ACE) and acetylcholinesterase (AChE) linked to ED. The phenolic constituent and amino acid content of the pumpkin seeds were also determined using high performance liquid chromatography with diode array detector (HPLC-DAD). This study revealed that all the pumpkin seed extracts inhibited PDE-5 (0 – 33.3 μg/ml), arginase (0 – 11.4 μg/ml), AChE (0 – 46.2 μg/ml), and ACE (0 – 10.02 μg/ml) in a concentration-dependent manner; with white melon seed having the highest enzyme inhibitory effects and kalabari the least. Furthermore, the amino acid analysis revealed both aspartate and arginine as the most dominant amino acids in all the samples with white melon also having the highest content and kalabari the least. The phenolic constituent as determined by the HPLC-DAD analysis revealed luteolin (10.2 mg/g) as the dominant phenolic compounds in white melon, quercitrin (5.2 mg/g) in fluted pumpkin and caffeic acid in kalabari; with white melon seed (10.2 mg/g) also having the highest phenolic content and kalabari (0.6 mg/g) the least. The enzyme inhibitory effect of the selected pumpkin seeds may be due to their phenolic constituents as well as their arginine and aspartate contents. Hence, these may be the possible underlying principles responsible for the erectogenic properties of these pumpkin seeds as obtained in folklore.
