ANTIBACTERIAL EVALUATION, REDUCING POWER ASSAY AND PHYTOCHEMICAL SCREENING OF MORINGA OLEIFERA LEAF EXTRACTS: EFFECT OF SOLVENT POLARITY

Moringa preparations have been cited in the scientific literature as having antibiotic, antitrypanosomal, hypotensive, and antispasmodic, antiulcer, anti-inflammatory, hypo-cholesterolemic, and hypoglycemic activities, as well as having considerable efficacy in water purification by flocculation, sedimentation, antibiosis.  To evaluate the antioxidant activity of Moringa oleifera leaf extracts and their in- vitro antibacterial activity against four microorganisms, viz. Escherichia Coli, Bacillus subtilis, Staphylococcus aureus and Salmonella typhii. Phytochemical screening of the leaf extracts in solvents of varying polarity; viz., water, methanol, ethanol and acetone were also carried out. The antioxidant activity of the extracts was determined by the reducing power assay using ascorbic acid as standard.  Well diffusion method was used to assess the antimicrobial effect of the extracts on both Gram positive and Gram negative micro-organisms. Well known chemical procedures were used for the detection of the phytochemical components. The aqueous extract exhibited maximum antioxidant activity compared to the organic solvent extracts. Acetone extract showed broad spectrum antimicrobial effect against all the tested micro-organisms while the methanolic extract was active against all microorganisms used, except E. coli.  The ethanolic extract was active against Salmonella typhii, and Staphylococcus aureus whereas the aqueous extract exhibited an inhibitory effect on Staphylococcus aureus only. The phytochemical screening indicated the presence of phenolics, flavonoids, tannins, glycosides etc., in the extracts. We believe that the higher reducing power of the aqueous extract could be due to the better solubility of the antioxidant components in water whereas the predominant antibacterial activity in organic solvent extracts as compared to aqueous extracts, indicates that the active components responsible for the bactericidal activity are more soluble in organic solvents. These studies provide an evidence to support traditional medicinal uses of the plant.