Separation and antioxidant properties of anti-lipid peroxidation fraction from Toona sinensis leaves

In order to search for a natural antioxidant applicable for oil, fraction with anti-lipid peroxidation (FTAP) was purified from Toona sinensis leaf extracts. Effects of pH value, heat treatment and storage time on the antioxidant activity of FTAP were investigated. The suitability of FTAP as an antioxidant in lard and vegetable oil was examined. Antioxidant activity was evaluated using linoleic acid peroxidation method. Macroporous resin was used for purifying FTAP. Content of flavonoids in FTAP was assayed with spectrophotometric method. Inhibition for linoleic acid peroxidation was emplied for monitoring antioxidation of FTAP at different pH values, heat treatment and storage duration. Peroxidation value was used as a criterion to assay antioxidant activity of FTAP in oil. LSA-10 was considered as optimal macroporous resin for FTAP. Anti-lipid peroxidation of FTAP could be correlated with content of flavonoids. The antioxidant activity of FTAP was maximum at pH 7 or pH 4 and remained unchanged at 185℃ for 60 min. FTAP stored at 5℃ in the dark was stable for 30 days, after that the antioxidant activity was reduced. FTAP reduced lipid peroxidation significantly in lard and vegetable oil in a dose-dependent manner, and 0.02% FTAP matched 0.02% butylated hydroxytoluene(BHT). FTAP is a potential source of natural antioxidants, and can be applied in oil or rich-oil foods.