Antimicrobial Activity and Time-kill Kinetics of Moringa oleifera Lam. Leaf Extracts Against Human Pathogenic Bacteria

Moringa oleifera Lam. exhibits various pharmacological activities, including antibacterial, antioxidant, and anti-inflammatory effects. This study aimed to investigate the antimicrobial properties of M. oleifera leaf extracts and their time-kill kinetics against human pathogenic bacteria. Fresh M. oleifera leaves were collected, cleaned, dried, and extracted with ethanol. Phytochemical screening and total flavonoid content (TFC) were determined. Antimicrobial activity against Staphylococcus aureus, S. epidermidis, Escherichia coli, and Pseudomonas aeruginosa was assessed via disk diffusion, minimum inhibitory concentration (MIC), minimum bactericidal concentration (MBC), and time-kill kinetics. Phytochemical analysis revealed the presence of flavonoids, alkaloids, terpenoids, tannins, and saponins, with a TFC of 8.95 mgEQ/g. Antibacterial testing demonstrated that higher concentrations of moringa leaf extract (2%, 4%, 6%, and 8%) produced larger inhibition zones, with the 8% concentration showing the most significant (p < 0.005) effect, particularly against Staphylococcus aureus (9.89 ± 0.28 mm), Staphylococcus epidermidis (9.59 ± 0.17 mm), Pseudomonas aeruginosa (9.05 ± 0.12 mm), and Escherichia coli (9.00 ± 0.27 mm). The MIC for all tested bacteria was 1.25 mg/mL, and the MBC ranged from 1.25 to 5 mg/mL. Time-kill assays showed that the extract was bactericidal to S. aureus and S. epidermidis at 4 x MIC, with complete bacterial elimination after 4 hours. However, P. aeruginosa and E. coli exhibited a reduction of more than 3 log10 CFU/mL, indicating bactericidal activity at higher concentrations. These findings support moringa leaf extract as a potential natural alternative for combating bacterial infections, particularly against Gram-positive bacteria.