Antimicrobial Activity evaluation and phytochemical screening of Silene macrosolen and Solanum incanum: A common medicinal plants in Eritrea.

Abstract Medicinal plants play great roles in the treatment of various infectious diseases. S.macrosolen and S.incanum are both important medicinal plants used traditionally for treatment of infectious diseases in many places around Eritrea. The periodically emerging new and old infectious microorganisms greatly magnify the global burden of infectious diseases. 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. Therefore, the search of new or alternative mechanisms to effectively treat and prevent infectious diseases, particularly bacterial diseases, have to be encouraged to effectively reduce these global burden. The objective of the study is to evaluate the in vitro antibacterial activities of the aqueous and solvent crude extract of leaf and stem of S.macrosolen, and leaf and root of S.incanum against standard strains of selected bacterial species, which can in turn provide a clue for the identification of active constituent responsible for the antibacterial activity. The antibacterial activity of the aqueous ( cold and hot water) and solvent extracts (ethanol, methanol, and chloroform) were evaluated on different selected bacterial strains (E.coli, S.aureus, and P.aeruginosa) using agar well diffusion method on Mueller-Hinton agar at different concentration with the presence of positive control (Chloramphenicol and ciprofloxacin) and negative control (sterile distilled water and 5%DMSO) controls. The highest inhibition zone was observed for methanol extracted S.macrosolen stem and chloroform extracted S.incanum root against S.aureus at 400mg/ml with 23mm and 24.5mmrespectively. Methanol and cold aqueous extracted S.macrosolen stem also showed the highest inhibition of 26mm, 23mm diameter, against P.aeruginosa, and E.coli respectively. The reason for the high inhibition zone could be due to the presence of secondary metabolites such as saponins, tannins, flavonoids, phenols and glycosides. The least result was seen in hot aqueous extract for each plant with no inhibition for all the bacteria. MIC and MBC was determined using tube dilution and plating method for those plant extracts which showed highest and consistent inhibition zone at different concentrations. The MIC and MBC of cold aqueous extract of S.macrosolen stem was found at 25mg/ml, and 50mg/ml respectively, against both E.coli and P.aeruginosa, while the MIC of chloroform extracted S.incanum root was found at 50mg/ml, however, the MBC was not determined in the concentration tested against S.aureus. The paper published after getting the results of the investigation would be anticipated to contribute for the resolution of the burden of the drug resistant bacteria species.