Psidium guajava Linn and Gongronema latifolium Benth Leaves Exhibit Potential Antimicrobial Therapeutics Against Some Clinical Pathogens

Background: The proliferation of antimicrobial resistance against synthetic pharmaceutical compounds highlights an exigent need to explore natural reservoirs to discover novel antimicrobial therapeutic agents. This study investigates the antimicrobial effectiveness of methanolic extracts obtained from Psidium guajava and Gongronema latifolium leaves. Methods: The coarse powder of dried leaves from Psidium guajava and Gongronema latifolium was subjected to cold maceration using 95% and 70% methanol to extract their phytonutrients. Utilizing the agar-well diffusion method, the antimicrobial susceptibilities of each distinct organism to the leaf extracts and their combinations were assessed. Methanol (5%) served as the negative control, while Levofloxacin (6.25μg/mL – 50μg/mL) for bacteria and Ketoconazole (20μg/mL – 160μg/mL) for fungi were employed as standard. Evaluation of Minimum Inhibitory Concentrations (MICs) for leaf extracts was conducted utilizing the agar well dilution technique, using a range of concentrations (5mg/mL – 15mg/mL). The concentrations tested ranged from the highest permitting growth to the lowest inhibiting growth across diverse microorganisms. Results: Psidium guajava exhibited significant antibacterial activity against all tested bacterial pathogens, including P. aeruginosa, S. aureus, E. coli, and B. subtilis. Conversely, Gongronema latifolium specifically inhibited the growth of B. subtilis and S. aureus, with no observable antimicrobial effect against E. coli and P. aeruginosa. None of the extracts demonstrated antimicrobial effects on fungal growth in this study. Conclusion: The Psidium guajava leaf emerges as a potent broad-spectrum antibacterial agent, surpassing the activity of the Gongronema latifolium leaf. Both leaves, from Psidium guajava and Gongronema latifolium, hold significant promise as rich sources of bioactive antibacterials.