In Vitro Evaluation of the Antimicrobial Activity of Azadirachta Indica (Neem) Leaf Extracts against Microbial Isolates from the Midwest in the United States

Abstract

The increasing resistance of microorganisms to standard antimicrobial drugs has created a growing need for alternative therapeutic agents from natural sources. This study evaluated the antimicrobial activity of aqueous, methanolic, and ethanolic extracts of Azadirachta indica (neem) leaves against selected bacterial and fungi. Neem leaves were extracted using water, methanol, and ethanol, and the antimicrobial activity of the extracts was assessed using the disc diffusion method. Test organisms included Staphylococcus aureus, Enterococcus faecalis, Salmonella typhi, Pseudomonas aeruginosa (ATCC 27853), Candida albicans, Aspergillus fumigatus, and Penicillium camemberti. Minimum inhibitory concentration (MIC) and phytochemical screening were also carried out, with the results showed that all extracts exhibited antimicrobial activity against the test organisms, with the ethanolic extract demonstrating the highest inhibitory activity, while the aqueous extract showed the lowest activity. Zones of inhibition increased with extract concentration. Moreover, antifungal activity was also observed, particularly with methanolic and ethanolic extracts. Phytochemical screening revealed the presence of alkaloids, tannins, saponins, flavonoids, phlobatannins, terpenoids, glycosides, steroids, phenol, oil and reducing sugar which may contribute to the observed antimicrobial activity. The Azadirachta indica leaves possess bioactive compounds with potential antimicrobial and antifungal properties and may serve as a promising source of plant-derived therapeutic agents for the control of pathogenic microorganisms.