ABSTRACT
The aqueous methanolic extracts of 20 selected plant parts were screened for in-vitro antimicrobial activity against clinical strains of Staphylococcus aureus, Bacillus subtilis, Klebsiella pneumonia, Salmonella typhi, Escherichia coli, Pseudomonas aeruginosa, Aspergillus niger and Candida albicans at a test concentration of 10mg/ml using the agar well diffusion method and penicillin G, chloramphenicol and Nystatin as controls. The seeds of Parkia biglobosa, Glycine max, Voendzeia substerrana, Arachis hypogeal, Cajanus cajan, Samonea saman, Manihot esculenta (root bark) Uapaca esculenta (stem bark and root bark), exhibited no meaningful anti-microbial activity against all the tested organisms. Uapaca esculenta (leaf) exhibited significant activity against kleb. (IZD= 16mm), Samanea saman (stem bark and leaves) showed significant anti-staphylococcus aureus activities (IZD=17mm, 15mm respectively) which compared favourably to the controls penicillin G and chloramphenicol. Detarium microcarpum (seed), Phyllanthus mullerianus (leaf) and Phyllanthus discoideus (leaf) exhibited a broad spectrum anti-microbial activity against all the test microorganisms with IZD’s ranging from (10mm – 20mm) an indication that they could be effective in severe bacterial infections. Interestingly to know is the anti-staphylococcus activity. (IZD=19mm) leaf extract higher than the control penicillin G (IZD=17mm). Crude 95% aqueous methanolic extract of Phyllanthus discoideus (yield = 29.75%) gave 14.315% of hexane solubles, 13.965% of ethylacetate solubles, 70.194% of absolute MeOH solubles and 1.624% of absolute MeOH insolubles. These solubility fractions were similarly screened in vitro for anti-microbial activity against the same microorganisms. The absolute methanol soluble fraction displayed the widest spectrum of antimicrobial activity (IZD range 9mm-24mm). particularly noteworthy are the anti-E.coli activities of the absolute MeOH soluble fraction (IZD = 20mm), and its precipitate (IZD=18mm) and the anti-salmonella typhi activity (IZD=17mm), its precipitate (IZD=15mm), against chloramphenicol and penicillin G – resistant strains of E.coli and Salmonella typhi .These are accentuated compared to those of the crude extract. The most active absolute methanol soluble fraction was separated by PTLC in to fifteen bands on silica gel 60 GF254with solvent system acetone: chloroform:formic acid:water (6:6:1:05 v/v/v/v). The impure bands were further purified by using different elutants of increasing polarities into twelve additional fractions. The twenty seven fractions were similarly screened invitro for anti-microbial activity against the same micro-organism. Bands 1A, 2A, 3A,4A and 8A displayed significant anti-microbial activity particulary against Staphylococcus aureus, Bacillus subtilis, Pseudomonas aureginosa & Klebsiella pneumonia which are comparable with that of controls. The glycosidic band 8A gave anti-Bacillus subtilis and anti-Staphylococcus aureus (IZD=18mm & 20mm respectively) which are comparable with that of the control penicillin G (IZD=20mm & 22mm respectively). The flavonoid glycosides 2A gave anti-Bacillus subtilis (IZD = 20mm, MIC 1.00mg/ml) which is the same as the control pencillin G (IZD = 20mm, MIC 1.037mg/ml). The phenolic fraction 1A and 9 gave anti-Candida albican activities which are comparable with that of Nystatin the control. Qualitative analysis of the bioactive bands/fractions using a combination of chemical and UV/visible spectrophotometric methods showed band 1A, 1B, 2A, 2B to contain tannins, flavonoids as glycosides while band 3 – 13 showed different form of glycosides and band 14 and 15 are phenolic compounds. The UV-spectra of the bands confirmed the phytochemical results for the presence of minor flavonoids of the isoflavonoid and flavones classes (λmax 207mm, 276mm) quinine glycosides (270nm – 275nm), flavan (λmax 207nm, 276nm) quinine glycosides (270nm – 275nm) This study reveals that a flavonoid glycosides, a minor flavonoid, alkaloids, Tannins are likely to be the active principles of Phyllanthus discoideus leaf with the possibility of synergistic action
