Abstract:
The burden of microbial infection and oxidative stress mostly in developing countries has propelled the continued search for potent antimicrobials and antioxidants from natural products especially plants of the Apocynaceae and Rubiaceae families. The present research was designed to screen the phytochemical constituents, antimicrobial and antioxidant properties of Tabernaemontanapachysiphonleaf and Mitragynaledermaniistem bark. The crude extract was obtained by cold maceration in methanol and subsequent drying. The extracts of both plants were subjected to fractionation using solvent partitioning with the following solvents in their order of polarity; n-hexane, dichloromethane, ethyl-acetate, and n-butanol. The extracts and the fractions of both plants were subjected to standard phytochemical screening. They were further tested for antimicrobial and antioxidant activities using standard methods. Seven pathogenic microbial organisms were used in the antimicrobial assay. The gram positive bacteria are staphylococcus aureus and Bacillus subtilis, the gram negative bacteria are Escherichiacoli, Pseudomonas aeruginosa and Salmonella shigellaand the fungi organisms are Candida albicans and Aspergillus niger. In addition, the extracts and fractions of Tabernaemontanapachysiphonleaf and Mitragynaledermanii stem bark at the concentrations of “15.63-1000 µg/ml” were screened for antioxidant potentials using in-vitro 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical scavenging method against ascorbic acid as the standard and Ferric Reducing antioxidant Power (FRAP) against gallic acid as the standard. The phytochemical screening of the extractof Tabernaemontanapachysiphon (TP) leaf and Mitragynaledermanii stem bark showed the appearance of Alkaloids, Flavonoids, Cardiac Glycosides, Saponines, Tannins and Steroids. The fraction showed distribution of the metabolites in tandem with polarities of the solvents. At all tested concentrations (200 mg, 400 mg and 500 mg) neither the crude extract of Tabernaemontanapachysiphon leaf and Mitragynaledermanii stem bark nor the fractions showed appreciable antimicrobial activity compared to the clinical isolates of bacteria and fungi used. However, crude extract of Tabernaemontanapachysiphon leaf and Mitragynaledermanii stem bark at the concentration of “500 µg/ml “97.43±0.497” showed appreciable antioxidant result. Interestingly, the ethyl-acetate fraction of Mitragynaledermanii showed appreciable antioxidant result “95.0±0.978” among others when compared to the standard. Although the extracts of these plants showed poor antimicrobial potential, their potent antioxidant activities lend credible support for the ethno medicinal uses of the plants as anti-stress and for possible modulation of inflammation.
