PHYTOCHEMICAL COMPOSITION AND ANTIBACTERIAL ACTIVITY OF WEST AFRICAN BLACK PEPPER (PIPER GUINEENSE) AQUEOUS AND ETHYLACETATE EXTRACTS AGAINST SELECTED BACTERIAL ISOLATES

ABSTRACT The increasing prevalence of antibiotic-resistant bacteria has necessitated the search for alternative antimicrobial agents from natural sources. This study investigated the phytochemical composition and antibacterial activities of West African black pepper (Piper guineense) seed extracts against selected clinical isolates, including Staphylococcus aureus, Escherichia coli, Pseudomonas aeruginosa, and Klebsiella pneumoniae. Phytochemical screening revealed the presence of bioactive compounds such as alkaloids, flavonoids, saponins, tannins, steroids, terpenoids, glycosides and phenolics which are known for their antimicrobial properties. Antibacterial activity was assessed using the agar well diffusion method at concentrations of 50–400 mg/mL, with gentamicin (20 mg/mL) serving as the positive control. The results showed that the aqueous extract exhibited the highest activity against Staphylococcus aureus (25 mm at 400 mg/mL), followed by Pseudomonas aeruginosa (22 mm) and Escherichia coli (18 mm). Ethylacetate extract demonstrated moderate activity, with inhibition zones of 14 mm, 10 mm, and 11 mm against Staphylococcus aureus, Escherichia coli, and Pseudomonas aeruginosa, respectively. No inhibitory effect was observed against Klebsiella pneumoniae at any concentration. These findings confirm the antimicrobial potential of Piper guineense seed extracts, particularly the aqueous extract, against bacterial pathogens. However, further research should be carried out to isolate and identify the specific bioactive compounds in Piper guineense seed extracts responsible for the antibacterial activity, particularly in the aqueous extract, to understand their mechanism of action.