EFFECTS OF FLAVONOIDS ON THERMAL AUTOXIDATION OF PALM OIL - STRUCTURE-ACTIVITY-RELATIONSHIPS

The effects of several flavonoids and other known antioxidants on the thermal autoxidation of refined, bleached and deodorized (RBD)-palm oil were studied. The lipid peroxidation was indexed by measuring the malonyldialdehyde (MDA) production using the 2-thiobarbituric acid (TBA) test. The antioxidative action decreased in the order of morin > kaempferol > myricetin > quercetin > vitamin A > α-tocopherol > apigenin > (+)-catechin > chrysin > datiscetin > luteolin > naringin > taxifolin > rutin > butylated hydroxytoluene (BHT) > naringenin. The flavonoid aglycones were more potent in their antiperoxidative action than their corresponding glycosides. Structure-activity revealed that the flavonoid molecule with polyhydroxylated substitutions on rings A and B, a 2-3 double bond, a free 3-hydroxyl substitution and a 4-keto moiety, would confer potent antiperoxidative properties upon the compound. The flavonols, namely morin, myricetin, kaempferol and quercetin, would be suitable potential antioxidants for use in the stabilization of RBD-palm oil and its fractions against thermal autoxidation. The structural activity of the flavonoids on the RBD-palm oil was similar to those observed for these compounds in animal tissue or enzyme systems. © 1990 AOCS Press.