A Comparative and Dose-dependent Evaluation on Stevia rebaudiana Antimicrobial Activity; A Challengeable Study

Comparative and dose-dependent evaluation of antimicrobial potential of Stevia rebaudiana (Bertoni) Bertoni was aim of current study. Six solvents were used for extraction of S. rebaudiana leaves to compare the effect of different solvents. These extracts were confronted against six selected pathogens. To determine the effect of dose on S. rebaudiana antimicrobial activity, nine concentrations were prepared for every extract to check against every mentioned pathogen using spot diffusion technique which taking of different concentrations is a prominent feature of present study in comparison with similar studies. Results were recorded by measuring the diameter zone of inhibition (DZI). Broth dilution method was also used to determine the minimum inhibitory concentration (MIC). Among six extracts, acetone extract revealed the best results against all pathogens except A. hydrophila. Furthermore, acetone extract showed better antimicrobial potential against G+ microorganisms than G¯ ones. Ethanol extract was most effective extract to inhibit A. hydrophila. No or a little activity was revealed by water and hexane extracts. Among six microorganisms, the most susceptible one was B. cereus exhibiting largest DZIs by all extracts. In MIC results, acetone extract revealed better results than ethanol and methanol extracts against all microorganisms, but this excellence was significant just against S. aureus and E. coli (p<0.05). Present study greatly proved S. rebaudiana has powerful antimicrobial potential and this feature is highly affected by solvent type and dose. S. rebaudiana can be used in food and pharmaceutic industries for either prevention or treatment.