Characterization of the total free radical scavenger capacity of vegetableoils and oil fractions using 2,2-diphellyl-1-picrylhydrazyl radical

The total free radical scavenger capacity (RSC) of 57 edible oils from diff erent sources was studied: olive (24 brands of oils), sunflower (6), safflo wer (2), rapeseed (3), soybean (3), linseed (2), corn (3), hazelnut (2), wa lnut (2), sesame (2), almond (2), mixture of oils for salad (2), "dietetic" oil (2), and peanut (2). Olive oils mere also studied according to their g eographical origins (France, Greece, Italy, Morocco, Spain, and Turkey). RS C was determined spectrophotometrically by measuring the disappearance of t he radical 2,2-diphenyl-1-picrylhydrazyl radical (DPPH.) at 515 MI. The dis appearance of the radical followed a double-exponential equation in the pre sence of oils and oil fractions, which suggested the presence of two (fast and slow) groups of antioxidants. RSC was studied for the methanol-soluble phase ("methanolic fraction", MF) of the oil, the fraction nonsoluble in me thanol ("lipidic fraction", LF), and the nonfractionated oil ("total oil"; TF = MF + LF). Only olive, linseed, rapeseed, safflower, sesame, and walnut oils showed significant RSC in the MF due to the presence of phenolic comp ounds. No significant differences were found in the RSC of olive oils from different geographical origins. Upon heating at 180 degrees C the apparent constant for the disappearance of RSC (k(T)) and the half-life (t(1/2)) of RSC for MF, LF, and TF were calculated. The second-order rate constants (k( 2)) for the antiradical activity of some phenolic compounds present in oils are also reported.