Antimicrobial efficacy of the extract, fractions and essential oils from the leaves of Eugenia uniflora Linn (Myrtaceae)

Abstract

Eugenia uniflora leaves is employed in Nigerian traditional system of medicine for the treatment of cough, bronchitis, skin and wound infections. In this study, the in vitro antimicrobial activities of the methanolic extract, fractions and essential oils from the leaves of Eugenia uniflora were investigated on some multidrug resistant pathogens. The essential oil was obtained by hydrodistillation and its chemical profile was determined through GC and GC-MS analysis while the extracts were obtained by maceration with methanol followed by a mild liquid/liquid fractionation process. Antimicrobial activity of the test samples against Staphylococcus aureus, Klebsiella pnemoniae, Pseudomonas aeruginosa, Candida albicans and Trichophyton rubrum were determined using the agar well diffusion technique. The results showed that the GC-MS analysis of the essential oil yielded fifty one compounds; with benzofuran (17.23 %) as the major compound. Ethyl acetate extract exhibited largest inhibition on S. aureus, K. pnemoniae, P. aeruginosa, C. albicans and T. rubrum with diameter mean zones of inhibition (DMZI) 25.0 ± 1.0 mm, 23.0 ± 0.4 mm, 9.0 ± 0.3 mm, 22.7 ± 0.3 mm, and 21.0 ± 0.8 mm respectively. Hexane, methanol and aqueous extracts of E. uniflora gave DMZI range of 8.0-21.7 mm respectively on the tested isolates while essential oil exhibited DMZI range of 7.7-18.3 mm. The minimum inhibitory concentration (MIC) of the leaf test samples from E. uniflora ranged between 6.25-100 mg/ml, minimum bactericidal concentration (MBC) and minimum fungicidal concentration (MFC) ranged between 12.5-100 mg/ml. The death rate on the most susceptible bacterial isolate (Staphylococcus aureus) occurred at 45 min in 0.5 ml ethyl acetate (EtOAc) fraction. The mode of action of the EtOAc fraction on S. aureus cell was demonstrated to be by protein leakage. The results obtained in this study have implications in the use of E. uniflora leaves as an antimicrobial agent and hence may provide a drug lead for pharmaceutical preparations.

Keywords: Antimicrobial efficacy, essential oil, extracts, Eugenia uniflora, Myrtaceae, multidrug resistant pathogens