ANTIBACTERIAL AND ANTIOXIDANT ACTIVITIES OF ETHANOLIC EXTRACT OF GUAVA (PSIDIUM GUAJAVA L.) LEAVES
Sohini Chatterjee and Narayan Chandra Mandal*
ABSTRACT
Ethanolic extract of shed dried and powdered leaves of Psidium guajava L. collected from Murshidabad district exhibited very good antibacterial activity against Gram positive bacteria viz. Staphylococcus aureus, Bacillus subtilis, Listeria monocytogenes and Gram negative bacterium Escherichia coli when tested by disc diffusion method. It has slight inhibitory effect against Pseudomonas aeruginosa but was unable to produce zones of inhibition against Salmonella typhimurium during in vitro study. By counting the colony forming units, minimum inhibitory concentration (MIC) was decided as 4 mg/ml in case of Gram positive bacteria and 5 mg/ml in case of Gram negative bacteria. A remarkable decrease in the number of CFUs indicated cidal mode of action of the leaf extract against the Gram positive bacteria but in case of Gram negative bacteria, pattern of CFU decrease in treated set suggested the bacteriostatic mode of action of the leaf extract. The extract also had very strong antioxidant property with IC50 value 4.1 ?g/ml.
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