MOLECULAR AND MICROBIOLOGICAL ASSESSMENT OF STEVIA (Stevia rebaudiana BERTONI) LEAF EXTRACTS FOR ANTI-BACTERIAL AND ANTI-MUTAGENIC ACTIVITIES

The purpose of the study is to assess the anti-bacterial and anti-mutagenic activities of Stevia rebaudiana leaf extracts on some pathogenic bacteria. Two extracts had been tested which prepared by two different solvents. Acetone extract was more effective as anti-bacterial than ethyl alcohol extract. Acetone extract showed high activity against Gram-positive bacteria which recorded (20 mm) while it recorded (18 mm) against Gram-negative bacteria. The study enhanced the antibacterial activity of Stevia rebaudiana leaf extracts using different solvents. The effectiveness of stevia extract as anti-mutagenic agent on Pseudomonas aeruginosa was also evaluated. The results of induction of prophage F₁₁₆ from P. aeruginosa after treated with different concentrations from each stevia extracts with ascorbic acid as negative control showed that stevia extract has no mutagenic activity on the tested bacteria. Moreover, the concentrations of ethyl methanesulfonate (EMS) when used as positive control showed a mutagenic effect. However, 100 mg/ml of stevia extract had reduced mutagenic activity of EMS. This finding suggested that stevia leaf extract may be playing a remarkable role in anti-mutagenic response. Susceptibility of the bacterial strain to exposure to different mutagenic and non-mutagenic agents has been assessed by analysis the variation of protein profile banding pattern (SDS-PAGE). The comparison between banding pattern when bacteria treated with each of stevia leaf extract, ascorbic acid and EMS, demonstrated that concentration 100 mg/ml of stevia leaf extract had significant effect to reduce the effect of the EMS as mutagenic agent in bacteria. Results from this study suggest that natural products like stevia leaf extract could be as an effective agent reducing the effect of the mutagenic agents. In addition to the antimicrobial properties which can be applied in the medical field that requires further studies and development.