Evaluation of the in vitro antibacterial activity of the solvent fractions of the leaves of Rhamnus prinoides L’Herit (Rhamnaceae) against pathogenic bacteria

Yalew Molla,Workineh Shibeshi,Getachew Tadesse,Teshome Nedi,Haile Alemayehu

doi:10.1186/s12906-016-1279-6

Abstract

BackgroundMedicinal plants play great roles in the treatment of various infectious diseases. Rhamnus prinoides is one of the medicinal plants used traditionally for treatment of bacterial diseases. The antibacterial activity of the crude extract of the plant had been shown by a previous study, but this study was undertaken to further the claimed medicinal use of the plant by screening its solvent fractions for the said activity so that it could serve as a basis for subsequent studies.MethodsThe solvent fractions of the plant were obtained by successive soxhlet extraction with solvents of increasing polarity, with chloroform and methanol, followed by maceration of the marc of methanol fraction with water. The antibacterial activity of the solvent fractions was evaluated on seven bacterial species using agar well diffusion method at different concentrations (78 mg/well, 39 mg/well and 19.5 mg/well) in the presence of positive and negative controls. The minimum inhibitory concentration of the solvent fractions was determined by micro-broth dilution method using resazurin as indicator.ResultMethanol and chloroform fractions revealed antibacterial activities against the growth of test bacterial strains with varying antibacterial spectrum and the susceptible bacterial species were Staphylococcus aureus, Streptococcus pyogen, Streptococcus pneumoniae and Salmonella typhi. The average minimum inhibitory concentration value of the methanol and chloroform fractions ranged from 8.13 mg/ml to 32.5 mg/ml and from 8.13 mg/ml to 16.25 mg/ml, respectively.ConclusionThe methanol and chloroform fractions demonstrated significant antibacterial activities against the growth of pathogenic bacteria but the aqueous fraction did not reveal antibacterial activity against any of the test bacteria.

Highlights

Medicinal plants play great roles in the treatment of various infectious diseases
Antibacterial activity The growth of test bacterial strains was inhibited by the tested concentrations of the crude extract, the methanol fraction and chloroform fraction of the leaves of Rhamnus prinoides in concentration dependent manner (Tables 1, 2 and 3)
Similar to the crude extract, the most susceptible bacterium against methanol fraction was standard strains of S. aureus followed by standard strains of S. pneumoniae with a mean zone of inhibition of 16.17 mm and 16 mm, respectively, at 78 mg/well concentration

Summary

Introduction

Medicinal plants play great roles in the treatment of various infectious diseases. Rhamnus prinoides is one of the medicinal plants used traditionally for treatment of bacterial diseases. The periodically emerging new and old infectious diseases greatly magnify the global burden of infectious diseases [3]. The majorities of emerging infectious events are caused by bacteria which can be associated with evolution of drug resistant strains and overwhelming of the natural host defenses [4, 5]. The search of new or alternative mechanisms to effectively treat and prevent infectious diseases, bacterial diseases, have to be encouraged to effectively reduce these global burden. Medicinal plants have been used for treatment of different infectious diseases and accepted as alternative approaches. In Africa, 90 % of the population relies on traditional healers to meet their primary healthcare needs [6] which indicate the presence of many medicinal plants with a potential source of new drugs

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