Bactericidal properties of mangrove Bruguiera cylindrica (L.) Blume leaf and Rhizophora mucronata Poir. stilt root extracts on Vibrio cholera, MTCC 435 and Escherichia coli pathogens

This research aimed to determine the bactericidal and cytotoxic properties of two mangrove plants commonly used in traditional medicine: Bruguiera cylindrica (leaf) and Rhizophora mucronata (stilt root). The selected plant parts were subjected to solvent polarity-based extraction. Of the solvent extracts, the acetone, ethyl acetate leaf extract of B. cylindrica and acetone stilt root extract of R. mucronata were chosen for further study as they exhibited minimum inhibitory and bactericidal concentrations between 0.5 and 1.0 mg.ml-1 against MTCC 435, Vibrio cholerae and Escherichia coli. The well and disk diffusion analysis of these mangrove extracts showed inhibition zone between 6 – 16 mm diameter for the bacterial pathogens. Similarly, the mangrove extracts displayed > 98 % reduction of viable counts for MTCC 435, E. coli and V. cholerae at different time intervals between 8 – 16 h. Electron microscope analyses of the bacterial cells treated with mangrove extracts confirmed the bactericidal properties by cellular aggregation and leakage. Further, the cytotoxicity evaluation of mangrove extracts with Henrietta Lacks cell lines did not show any viability interference up to 200 μg.ml-1, indicating their non-toxicity to human cells and biocompatibility for drug development. The research findings suggest that the acetone, ethyl acetate leaf extract of B. cylindrica and the acetone stilt root extract of R. mucronata could be used as a bactericidal resource against V. cholerae, MTCC 435 and E. coli.