Antimicrobial Potential of Stevia rebaudiana Leaves Extract Against Selected Bacterial and Fungal Strains

The antimicrobial potential of leaves extract of indigenous Stevia rebaudiana is investigated to treat infectious diseases. For this purpose, leaf extracts were prepared in two solvents, ethanol and water. The crude extract was tested against four bacterial and one fungal strain (Aspergillus flavus). Out of four bacterial strains, two were gram-positive, Staphylococcus aureus and Lactobacillus acidophilus, whereas Salmonella typhi and Escherichia coli were gram negatives. Clarithromycin and erythromycin were used as a positive control for bacterial growth. However, Terbinafine was used as a positive control against fungal strain, while DMSO was used as a negative control. Results showed that the ethanolic extract of Stevia showed higher antibacterial activity as compared to water extract against all the bacterial strains. The zone of inhibition against E.coli was 5.66mm. Lactobacillus acidophilus clear zone of inhibition in the ethanolic extract was 9.3mm. Similarly, the ethanolic extract of leaves showed inhibition against Staphylococcus aureus and Salmonella typhi, with an average zone of inhibition (7.33mm and 7.66mm). These findings suggested that leaves extracts have inhibitory activities against bacterial strains, although their antibacterial activities are lower than that of the standard that is Clarithromycin and Erythromycin. Leaves extract of Stevia showed no activity against Aspergillus flavus. It was concluded that Stevia rebaudiana ethanolic extract could be used as an antibacterial agent against selected pathogens due to its significant activity. In contrast, no significant activity against fungal pathogen was observed in both extracts.