In vitro Evaluation of Anti-quorum Sensing and Anti-microbial Activity of Azadirachta indica and Acacia Nilotica Extracts

Abstract

Background: Quorum sensing-mediated biofilm formation enhances bacterial virulence and antimicrobial resistance, prompting the exploration of plant-derived compounds as alternative therapeutic agents Aim: To determine the anti-quorum sensing and antimicrobial activity of ethanol extracts of Azadirachta indica (Neem) and Acacia nilotica (Babul) against Gram-negative pathogenic organisms, Escherichia coli and Pseudomonas aeruginosa. Study Design: In vitro experimental study. Location and Time of Study: School of Life Sciences and Biotechnology, Chhatrapati Shahu Ji Maharaj University, Kanpur, India between January 2023 and March 2024. Methodology: Phytochemical screening of plant extracts was done using the Azadirachta indica leaves and Acacia nilotica bark. The anti-quorum sensing activity was measured using Chromobacterium violaceum MTCC 2556 by inhibiting violacein at concentrations of 50-200 mg/mL Agar well diffusion assay was used to determine antimicrobial activity against E. coli and P. aeruginosa. ANOVA was used to statistically analyze the results at p ≤ 0.05. Results Both extracts displayed concentration-dependent quorum sensing inhibition, with Acacia being significantly more active (****p < 0.0001) at 200 and 100 mg/mL respectively. Antimicrobial assays indicated a greater activity of Acacia against E. coli (~20 mm inhibition zone), while both extracts were less active against P. aeruginosa. Increased inhibition at elevated concentrations was considered to be due to the diffusion restrictions and phytochemical interactions. Conclusion: Acacia nilotica exhibits enhanced anti-quorum sensing and antimicrobial activity against E. coli and P. aeruginosa compared to Azadirachta indica, in support of its potential as a natural anti- virulence agent.