ANTIOXIDANT ACTIVITY OF STEVIA-REBAUDIANA

The antioxidant activity against sardine oil and linoleic acid of hot water extract from Stevia rebaudiana was compared to DL-alpha-tocopher ol (DL-alpha-Toc), butyl hydroxy anisol and green tea extract. The sar dine oil oxidation was assessed from the formation of peroxides. The c oncentration of odor components was measured by a portable type odor c oncentration meter equipped with a metal oxide semiconductor. Linoleic acid oxidation was assessed by the ferric thiocyanate method. Stebia rebaudiana extract effectively inhibited hydroperoxide and volatile co mponent formations in sardine oil. The oxidation was more effectively inhibited by the hot water extract from S, rebaudiana than DL-alpha-To c or green tea extract at the same concentration in sardine oil. Addit ive effects were observed when the extract was mixed DL-alpha-Toc or c itric acid. Some effective fractions were separated from the extract b y dialysis, column chromatography and thin layer chromatography. Some of the antioxidant fractions were polyphenolic compounds. The componen t which showed the highest antioxidant activity contained large amount s of potassium.