Aframomum melegueta (alligator pepper (AP)) and Aframomum danielli (bastered melegueta (BM)) seeds have been known to improve sexual function in folkloric medicine. This study investigates the effects of AP and BM seeds' alkaloid extracts on the activities of enzymes (acetylcholinesterase (AChE), angiotensin-1-converting enzyme (ACE), phosphodiesterase-5 (PDE-5), and arginase) relevant to erectile dysfunction (ED). Alkaloids from the seeds were prepared by the solvent extraction method and their interactions with AChE, ACE, PDE-5, and arginase were assessed. Gas chromatographic (GC) analyses of the extracts were also performed. The results revealed that the extracts inhibited the enzymes in a concentration-dependent manner. However, alkaloid extract from AP seed had higher AChE (IC50 = 5.42 μg/mL) and ACE (IC50 = 12.57 μg/mL) but lower PDE-5 (IC50 = 33.80 μg/mL) and arginase (IC50 = 31.36 μg/mL) inhibitory effects when compared to that of BM extract (AChE, IC50 = 42.00; ACE, IC50 = 60.67, PDE-5, IC50 = 7.24; and arginase, IC50 = 2.53 μg/mL). The GC analyses revealed the presence of senkirkine, angustifoline, undulatine, myristicin, safrole, lupanine, powelle, and indicine-N-oxide, among others. The inhibition of these enzymes could be the possible mechanisms by which the studied seeds were being used in managing ED in folklores. Nevertheless, the seed of AP exhibited higher potentials.
Keywords: alkaloid extracts; alligator pepper; bastered melegueta; enzymes; erectile dysfunction.