FLAVONOIDS AS STABILIZERS OF FISH-OIL - AN ALTERNATIVE TO SYNTHETIC ANTIOXIDANTS

The antioxidant activities against fish oil oxidation of six commercia lly available flavonoids and of five flavonoids purified from two Chil ean native plants were compared to those of dl-alpha-tocopherol and of two synthetic antioxidants, butylated hydroxytoluene and butylated hy droxyanisole. Among the commercial flavonoids, catechin, morin and que rcetin showed a higher activity when fish oil oxidation (either sponta neous or Fe2+-induced) was assessed from the formation of peroxides or thiobarbituric acid-reactive substances. Among the native flavonoids, the 5,3',4'-trihydroxy-7-methoxy flavanone (designated as Pt-2) showe d the highest antioxidant activity. Mixtures of quercetin or of Pt-2 w ith dl-alpha-tocopherol produced better inhibitory effects when compar ed to that of each substance assayed by itself. Also, when Pt-2 and qu ercetin were assayed in combination (0.3 g/kg oil and 0.7 g/kg oil, re spectively), a synergistic antioxidant effect was observed. Results in dicate that several flavonoids could be used as natural antioxidants a s a means to replace those synthetic antioxidants, the use of which ha s been questioned.