Antibacterial Activity of Gizawa (Withania somnifera) and Embuay (Solanum incanum) Leaf Extracts and Their Synergistic Effect Against Standard and Clinical Pathogenic Bacterial Isolates

Abstract

Infectious diseases are the world’s leading cause of death. The rapid growth of drug resistance microbes are unable to treat by the existing antibiotics. Plants are considered rich sources of bioactive compounds used to overcome those pathogens. Thus, this study was aimed to evaluate the antibacterial activity of ethanol, methanol, and chloroform crude leaf extracts of Withania somnifera, Solanum incanum and their mixtures against six selected pathogenic bacteria such as Escherichia coli (ATCC35218), Klebsiella pneumonia (ATCC700603), Staphylococcus aureus (ATCC25923) and their clinical isolates. Agar well diffusion was used to determine the inhibition zone of extracts, and broth dilution and agar well diffusion methods were used to determine the minimum inhibitory concentration and minimum bactericidal concentration (MBC). The inhibition zone of Withania somnifera extracts were range from to ; whereas the inhibition zone of Solanum incanum ranges from to . The greatest inhibition zone ( mm) was recorded in S. aureus (clinical isolate) subjected to methanol leaf extract of the plant mixture. The inhibition zone of the mixture was significantly (P≤0.05) greater than the separated plant extracts; and also most extracts of Withania somnifera were significantly (P≤0.05) greater than inhibition zones of Solanum incanum. Methanol extracts showed the highest inhibition zone against most of the tested bacterial strains, because it extracts a variety of bioactive compounds sufficiently. The crude extracts were showed different ranges of minimum inhibitory concentration and minimum bactericidal concentration. Moreover, the crude extracts were revealed the presence and absence of some bioactive constituents of the plant. Thus, the present finding supports the traditional use of Withania somnifera and Solanum incanum to treat different ailments. However, a detailed in vitro scientific study is needed to come up with comprehensive conclusions on the use of their synergistic extracts as alternative medicine. Key words: Antibacterial activity, Inhibition zone, MBC, MIC, S. incanum, synergetic effect, W. somnifera.