Phytochemical and antibacterial activity of <i>Mangifera indica</i> Linn (Mango) bark and leaf extracts on bacteria isolated from domestic wastewater samples

Abstract

Background: Wastewaters generated from ubiquitous use of water in daily human activities often contains various pathogenic microorganisms, which may contaminate surface or ground waters when released indiscriminately into the environment. Consumption of natural water resources polluted by such contaminated wastewaters may compromise public health and decrease the populations of aquatic organisms in such water  bodies. Mangifera indica (mango) plants have been widely used as remedy for treatment of a wide range of water borne ailments. This study  was  therefore conducted to identify bacteria contaminating wastewaters from domestic sources and to determine  the antibacterial potentials of mango  bark and leaf extracts against them.
Methodology: Wastewater samples were obtained from the wash areas of five randomly selected female hostels in Bowen University, Iwo, Osun State, Nigeria. Bacteria in the wastewater samples were isolated by standard aerobic cultures and identified using conventional biochemical test schemes. The antimicrobial activities of the methanol extracts of M. indica leaf and bark, and a standard antibiotic (tetracycline), were determined by the modified disc diffusion test. Phytochemical analysis of the extracts was determined by standard method, and the active compounds in them were analyzed by FT-IR spectroscopy using Agilent technologies FT-IR spectrometer at a scan range of 4,000-600 cm^-1.
Results: The bacterial species isolated from the wastewater samples included Escherichia coli, Proteus mirabilis, Salmonella spp, Pseudomonas aeruginosa and Klebsiella pneumoniae, with E. coli the most frequent (35.7%) and K. pneumoniae the least frequent (7.1%). Leaf extract (30µg) of M. indica exerted high antimicrobial activity against Salmonella spp (inhibition zone diameter of 15mm) while the bark extract exerted high antimicrobial activity against P. aeruginosa (inhibition zone diameter of 13mm). Comparatively, tetracycline (30µg) exerted highest antimicrobial activity against Salmonella spp (inhibition zone diameter of 18mm) but no activity against P. aeruginosa (inhibition zone diameter of 0 mm). The FT-IR analysis confirmed the presence of several functional groups with antimicrobial potentials such as flavonoids, alkaloids, tannins, saponins, phenols, and phytosterols.
Conclusion: These results indicate the antibacterial potential effects of M. indica leaf and stem bark extracts against some bacterial isolates, and thus may be recommended for biological treatment of water contaminated by wastewater sources.