Stevia rebaudiana is considered natural as source of antioxidants, which contained phenolic compounds and flavonoides at levels 24.01 and 18.93 mg/g dry weight basis of leaves and 33.99 and 30.03 mg/g dry weight basis of callus, these substances have been suggested to play a preventive role for human health. Antioxidant activity of water and methanolic extracts of stevia leaves and callus equivalent to gallic acid (GA) and butylated hydroxyl anisole (BHA) were determined. GA was the stronger antioxidant in both water and methanol extracts than BHA. Antibacterial and antifungal of stevia leaves and callus extracted by six types of solvent (acetone, chloroform, hexane, methanol, ethylacetate and water) were studied. Methanol and acetone extracts had greater antibacterial potential for the strains of Listeria monocytogenes, Staphylococcus aureus, Pseudomonas aeruginosa and Escherichia coli. However, acetone, chloroform, methanol and ethyl acetate had antifungal potential for Asperigillus ochraceus, Asperigillus parasiticus, Asperigillus flavus and Fusarium. The results indicate that stevia leaves and callus extracts may be an ideal candidate for further research into their uses for food preservation and pharmaceutical due to their antioxidants and antimicrobial activities.
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