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Comparative antimicrobial activity of fractions of Vernonia glaberrima against selected human pathogens

The increasing resistance of most microorganisms to existing armamentarium of antibiotics has made the search for new antimicrobial agents particularly from natural products more imperative. This study was aimed at evaluating the antimicrobial activity of the chloroform, ethyl acetate, n-hexane and n-butanol fractions of Vernonia glaberrima against some selected human pathogens with a view to identify the most active fraction from the plant and to ascertain the veracity of the use of the plant in ethno-medicinal practice. The antimicrobial activity of the fractions of V. glaberrima against eight selected human bacterial pathogens- Methicillin resistant Staphylococcus aureus , Vancomycin resistant enterococci, Methicillin Susceptible Staphylococcus aureus (MSSA), Listeria monocytogenes , Helicobacter pylori , Campylobacter fetus , Pseudomonas fluorescens , Proteus vulgaris and two fungal pathogens- Candida stellatoidea and Candida tropicalis was investigated using the agar well diffusion and broth dilution methods. The fractions exhibited good antimicrobial activity against the pathogens with the exception of L. monocytogenes , C. fetus , P. vulgaris and C. tropicalis . The Minimum Inhibitory Concentration (MIC) of the nhexane, chloroform and n-butanol fractions was 0.25 mg/mL while that of ethyl acetate fraction ranged between 0.25-0.125 mg/mL against all the test microorganisms. The Minimum Bactericidal/Fungicidal Concentration (MBC/MFC) of the n-hexane and n-butanol fractions was found to be 1 mg/mL, chloroform fraction had 0.5-1 mg/mL and the MBC/MFC of ethyl acetate ranged between 25-0.5 mg/mL. The ethyl acetate fraction possessed the most significant antimicrobial activity among the four fractions tested against the pathogens. Keywords:  Vernonia glaberrima ; Antimicrobial activity; Fractions