Antimicrobial Potentials, Phytochemical Screening and Determination of Bioactive Compounds from Three Indian Folk Medicinal Plants

Background: Globally, multidrug resistance has increased in both the society and health care systems related to bacterial infections which is impaired due to massive antimicrobial treatments. Therefore, we need efficient, non-toxic compounds from plant-based alternatives. The aim of the present study is to investigate the antimicrobial efficacy of leaf extracts with various solvents of Aegle marmelos, Plumbago zeylanica and Rhinacanthus nasutus against human pathogenic organisms. Methods: Antimicrobial properties of various extracts of A. marmelos, P. zeylanica and R. nasutus were investigated against human pathogenic organisms such as Acinetobacter baumannii, Salmonella enteriditis, Bacillus cereus, Streptococcus pneumonia, Mycobacterium tuberculosis and Aspergillus fumigatous by agar well diffusion method. Minimum Inhibitory Concentration (MIC), Minimum Bactericidal / Fungicidal Concentration (MBC/MFC) values were also evaluated by the microdilution method and the phytochemicals and functional groups using HPLC, GC-MS and FTIR analysis were identified. Results: Ethyl acetate leaf extract of P. zeylanica showed better antimicrobial activity against the tested pathogens, especially for S. pneumoniae (40 mm) followed by ethyl acetate extract of R. nasutus (36 mm) against S. pneumoniae. While the least inhibition zone was observed for the aqueous extract of P. zeylanica against S. enteritis (10 mm). The MIC value ranged from 3.75 μg/ml to 60 μg/ml and MBC/MFC 7.5 μg/ml to 60 μg/ml. Phytochemical analysis exhibited the presence of alkaloids, steroids, saponins, flavonoids, tannins, terpenes, phenolics and cardiac glycoside in all samples of selected plant extracts. Tannins, phenolics and glycoside were found only in the ethyl acetate extract of P. zeylanica. HPLC and GC-MS analysis of ethyl acetate leaf extract of P. zeylanica produced ten major peaks thus exhibiting eleven compounds respectively. The chemical nature of the leaf extract was analyzed by the FT-IR spectrum. Conclusion: Ethyl acetate leaf extract of P. zeylanica showed better antimicrobial activity than other extracts and even standard drugs. Therefore, this plant could be further considered for advanced research to identify active biomolecules in developing antimicrobial drugs.