ANTIBACTERIAL PROPERTIES OF Oscuim gratissium (SCENT LEAF) AGAINST SELECTED BACTERIA

The growing resistance of pathogenic bacteria to commonly used antibiotics has stimulated renewed global interest in medicinal plants as alternative sources of antimicrobial agents. One such plant, Ocimum gratissimum (commonly known as scent leaf), has long been utilized in traditional medicine due to its therapeutic properties. This study investigated the antibacterial activity of scent leaf extracts against selected bacterial pathogens. Fresh leaves of Ocimum gratissimum were procured, air-dried, and ground into powder. The powdered material was extracted using ethanol and distilled water to obtain ethanolic and aqueous extracts, respectively. The antibacterial effects of these extracts were evaluated against clinical isolates of Escherichia coli, Staphylococcus aureus, Pseudomonas aeruginosa, and Klebsiella pneumoniae, obtained from the University of Benin Teaching Hospital, using the agar well diffusion technique in accordance with Clinical and Laboratory Standards Institute (CLSI) guidelines. Phytochemical analysis of both extracts confirmed the presence of alkaloids, flavonoids, tannins, and saponins in varying concentrations, with the ethanolic extract exhibiting a higher abundance of these bioactive compounds. Antibacterial testing revealed a concentration-dependent inhibitory effect for both extracts, with reduced activity observed at lower concentrations. However, the ethanolic extract demonstrated superior antibacterial efficacy, producing inhibition zones of up to 15 mm against Staphylococcus aureus and 12 mm against Pseudomonas species at a concentration of 100 mg/mL. In contrast, the aqueous extract showed moderate activity, with inhibition zones ranging between 10 mm and 12 mm. The minimum inhibitory concentration (MIC) of the ethanolic extract was determined to be 50 mg/mL for S. aureus, E. coli, and Pseudomonas, while Klebsiella species required 100 mg/mL for inhibition. For the aqueous extract, MIC values were only observed at 100 mg/mL for E. coli and Pseudomonas. Furthermore, the minimum bactericidal concentration (MBC) of the ethanolic extract was 50 mg/mL for Staphylococcus aureus and Pseudomonas, and 100 mg/mL for E. coli, whereas Klebsiella species exhibited only bacteriostatic response. The aqueous extract showed bactericidal activity only against Pseudomonas at 100 mg/mL. Overall, the results indicate that Ocimum gratissimum possesses notable antibacterial properties, particularly when extracted with ethanol. These findings validate its traditional medicinal use and suggest its potential application in the development of plant-based antimicrobial agents.