Antimicrobial activity of medicinal plant leaf extracts against pathogenic bacteria

Abstract

To determine antibacterial activity of water, oil and methanol extracts of guava (Psidium guajava), green tea (Camellia sinensis), neem (Azadirachta indica) and marigold (Calendula officinalis) against different species of bacteria, Pseudomonas spp., Vibrio cholerae, Vibrio parahaemolyticus (V. parahaemolyticus), Klebsiella spp., Escherichia coli, Salmonella spp. and Staphylococcus aureus (S. aureus). Antibacterial activity of plant extracts was measured by agar well diffusion method. Boiled water extracts of guava leaf showed the largest zone of inhibition (22 mm) against V. parahaemolyticus. Water extracts of green tea leaf at boiling and room temperature showed 17.5 mm and 19 mm zone of inhibitions against V. parahaemolyticus and S. aureus, respectively. Boiled water extract of neem leaf showed moderate zone of inhibition against Escherichia coli (10 mm) and Klebsiella spp. (11 mm). Water and oil extracts of marigold leaf at both boiling and room temperature did not show any zone of inhibition against any of the tested microorganisms. Methanol extracts of both guava and green tea leaves showed same zone of inhibition against Pseudomonus spp. (18 mm). Methanol extract of neem leaf showed antibacterial acitivity against Klebsiella spp. (16 mm) and Vibrio cholerae (14 mm) and that of marigold leaf showed antimicrobial activity against S. aureus (18 mm) and Klebsiella spp. (12 mm). The results from the study suggest that the leaves of guava, green tea, neem and marigold show anibacterial activity against different bacterial species. They could be used as alternatives to common antimicrobial agents for treatment of bacterial infections.