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Moringa oleifera Lam and Pongamia pinnata Linn are the two well known tropical trees with a rich world wide histroy of folklore medicine. Attempts to revisit the medicinal potential of these trees are the need of the hour with emerging drug resistance among common pathogens. In this regard few common pathogens have been considered for testing against the possible antibacterial activity of the concerned plants. The flower extracts of the plants were examined for antibacterial activity against Escherichia coli, Klebsiella pneumonia, Psuedomonas aeruginosa and Staphylococcus aureus respectively. P.pinnata extract (aqueous, ethanol and fresh juice) seems to exhibit more effective antibacterial activity against E.coli, 65.25% more effectively than M.oleifera extracts and almost on-par with the control antibiotic. S.aureus also seems to exhibit more sensitivity to P.pinnata extracts, while better antibacterial activity against K.pueumoniae and P.aeruginosa could be seen with fresh juice extract of P.pinnata and solvent extract of M.oleifera respectively. The ethanol extract of the flowers were subjected to phytochemical analysis which indicated the presence of alkaloids, flavonoids and polyphenols in the extracts. The study asserts the prospective role of Pongamia and Moringa flower extracts as a source of natural and broad spectrum antibacterial compounds and opens up the need for further research on their use in the treatment of various bacterial infections and to discover the new bioactive compounds which can also be used for prophylactic treatment.

To examine the antibacterial activity of ethyl acetate, ethanol and methanol extracts of Azadirachta indica (A. indica) on fish pathogens viz., Aeromonas veronii, Aeromonas hydrophila, Acinetobacter junii, Acinetobacter tandoii, Acinetobacter spp. and Pseudomonas stutzeri isolated from diseased blackspot barb, Dawkinsia filamentosa. The naturally infected fish, D. filamentosa were collected from Mettur Dam and the associated bacteria in the ulcerative lesions were isolated, sequenced the amplified product and tentatively identified through sequence similarity. The leaves powder was extracted successively with 250 ml of ethyl acetate, ethanol and methanol solvents by using Soxhlet extractor for 8 h at a temperature not exceeding the boiling point of the solvent. Ethyl acetate, ethanol and methanol extracts were subjected to phytochemical analysis as well as the antimicrobial assay using agar well diffusion method. Totally six fish bacterial pathogens were isolated from the ulcerative of lesions blackspot barb fish (D. filamentosa). All the gene sequences were deposited in the NCBI and received their accession numbers. The isolated strains were: A. veronii (KX688046), P. stutzeri (KX721473), A. hydrophila (KX756709), A. spp. (KX775221), A. junii (KX756708) and A. tandoii (KX775222). The different crude extracts of A. indica showed significant inhibitory effects on all the isolates. In which, the ethyl acetate extract showed maximum zone of inhibition on against P. stutzeri (23 mm) A. junii (22 mm), A. hydrophila (19 mm) and A. tandoii (18 mm). The ethanol extract showed moderate zone of inhibition on A. junii (15 mm) and A. veronii (14 mm) and also the methanol extract on A. junii (15 mm) and A. veronii (14 mm). The present study revealed that the crude extracts A. indica leaves possesses significant antibacterial activity on isolated fish pathogens. The susceptibility test was conducted on isolates using antibiotics, selected based on their importance to human medicine and on fish production. To conclude the present findings the ethyl acetate leaf extracts could be used as potential sources of antimicrobial agents.