EFFECT OF ALKALOID EXTRACTS FROM AFRAMOMUM MELEGUETA AND AFRAMOMUM DANIELLI WITH SOME ENZYMES RELEVANT TO ERECTILE DYSFUNCTION

Abstract

This study sought to investigate the effect of alkaloid extracts from seeds of two common spices; alligator pepper (Aframomum melegueta) and bastered melegueta (Aframomum danielli) on some enzymes relevant to erectile dysfunction ED) (in vitro). Alkaloid extracts from the dried seeds of alligator pepper (AP) and bastered melegueta (BM) were prepared by soaking 50 g each of the sample in 500 ml of mixtures of ethanol and acetic acid (v/v:9:1). After 4 hours, the filtrate was decanted, dried, reconstituted in water and kept in a refrigerator. Then, the effects of the extracts were assessed on acetycholinesterase (AChE), arginase, angiotensin-1-converting enzyme (ACE) and phosphodiesterase-5 (PDE-5) activities. Furthermore, the ferric reducing antioxidant power (FRAP), 1,1-diphenyl-2-picrylhydrazyl (DPPH), 2,2-azinobis-3-ethylbenzo-thiazoline-6-sulfonate (ABTS), hydroxyl (OH) radicals scavenging abilities, Fe2+ chelating ability and inhibition of Fe2+ induced lipid peroxidation in rat’s penile homogenates were also investigated. The result revealed that both extracts inhibited the activities of the enzymes (AChE, arginase, ACE and PDE-5) in dose dependent manner. AP had higher inhibitory effect on AChE (IC50 =5.42 μg/ml) and ACE (IC50 =12.57μg/ml) than BM [AChE (IC50 = 42.00μg/ml); ACE (IC50 = 60.67μg/ml)]. The combination of different proportions of AP and BM extracts showed antagonistic effects on the AChE inhibitory property of AP. Conversely, BM had higher inhibitory effect on arginase (IC50 =2.53μg/ml) and PDE-5 (IC50 = 7.24μg/ml) than AP [arginase (IC50 = 31.36μg/ml); PDE-5 (IC50 = 33.80μg/ml)]. The combination of different proportions of AP and BM extracts had synergistic effects on arginase and PDE-5 inhibitory activities of AP. The extracts equally exhibited high antioxidant properties as typified by ferric reducing power, DPPH*, OH*, ABTS* scavenging and Fe2+ chelating abilities coupled with inhibition of Fe2+ induced lipid peroxidation in rat’s penile homogenate in vitro. The predominant alkaloids identified by gas chromatography in both extracts are myristicin and indicine- N- oxide. The inhibition of key enzymes relevant to erectile dysfunction coupled with the antioxidant activities of some alkaloid constituents from AP and BM could be part of the possible mechanism through which these plants elicit erectogenic function in folkloric medicine. Overall, alkaloid extract of AP may have better promising effects than the BM based on their antioxidative and some enzyme inhibitory activities. However, the combination of AP and BM may be potential strategy for the development of novel antioxidative and erectogenic agents.