Antibacterial Susceptibilities of Moringa Oleifera Leaf Extract (MOLE) Against Gram-positive and Gram-negative Bacteria: A Preliminary Study

Abstract

Introduction: The emergence of antibiotic-resistant bacteria, particularly Gram-positive methicillin-resistant Staphylococcus aureus (MRSA), along with methicillin-susceptible S. aureus (MSSA) and Gram-negative Escherichia coli (E. coli), highlights the critical need for new antibacterial approaches. Herbal medicines, particularly Moringa oleifera leaf extract (MOLE), have demonstrated potential in combating bacterial infections. This study assesses the antibacterial efficacy of MOLE against MRSA, MSSA, and E. coli, with a focus on its effectiveness against both resistant and non-resistant bacterial strains. Methods: The antimicrobial susceptibility of ethanolic extract of MOLE was evaluated using the Kirby-Bauer disk diffusion method at five different concentrations (50-800 mg/mL) against MRSA, MSSA and E. coli. The phytochemical composition of MOLE was analysed using liquid chromatography-mass spectrometry (LC-MS). Results: MOLE demonstrated dose-dependent antibacterial susceptibility against both MSSA and MRSA. For MSSA, inhibition zones increased from 11.40 ± 0.65 mm at 100 mg/mL to 21.67 ± 0.75 mm at 800 mg/mL. MRSA exhibited similar dose-response, with inhibition zones expanding from 9.33 ± 0.65 mm at 100 mg/mL to 17.00 ± 0.65 mm at 800 mg/mL, comparable to the positive control, cefoxitin (18.75 ± 0.65 mm). Notably, MOLE exhibited no inhibitory effect against E. coli. LC-MS analysis identified bioactive compounds, including flavonoids, alkaloids, phenolics, and glucosinolates, known for their antibacterial properties. Conclusion: MOLE exhibited significant antimicrobial susceptibility against MRSA and MSSA, but was ineffective against E. coli. Future research should aim to elucidate the mechanisms of action of MOLE, evaluate its safety and efficacy in vivo, and explore potential synergistic interactions with conventional antibiotics.