Evaluation of antibacterial activity of selected plant species from the State of Punjab, India

Abstract

Objective: Evaluation of antibacterial potential of aqueous and ethanol extracts of Solanum nigrum L., Eclipta alba (L.) Hassk., Achyranthes aspera L., Sida acuta Burm.f., Justicia adhatoda L. (Syn. Adhatoda vasica Nees), Boerhavia diffusa L. and Withania somnifera (L.) Dunal against human pathogenic bacteria Enterococcus faecalis, Escherichia coli, Pseudomonas aeruginosa and Staphylococcus aureus. Materials and Methods: Powdered form of the whole plant of each species was extracted in aqueous and ethanol solvents. The antibacterial activity experiment was performed using agar well diffusion method. A dose of 50µl, 100µl and 150µl of each extract (aqueous and ethanol) were tested. Results: Only the ethanol extracts have shown activity against test organisms. The 50µl and 100µl doses of extracts were not much effective against all the bacteria. Thus 150µl volume was selected for further study. The ethanol extract of Adhatoda vasica has yielded maximum zone of inhibition 24±1.7mm and 22±2.1mm against S. aureus and E. coli, respectively. Type AA₃ of A. aspera and SN₃ of S. nigrum were the most effective against E. faecalis with inhibition zones 22±2.2mm and 21±2.2mm, respectively. Similarly, B. diffusa has shown maximum inhibition against P. aeruginosa. Conclusion: The present study suggests the use of ethanol extract since none of the aqueous extracts have shown activity against all the tested bacteria. The difference in activity of different plant extracts may be due to variable chemical composition of the plant species. The plant species can be selected based on the bacterial species to be investigated. Further studies can be planned to understand the bioactive molecules responsible for antibacterial activity.