Antioxidant activity of phytic acid in lipid model system

Abstract

Free radicals formed during thermal (60 °C, 24 h) and catalytic (Fe2+ ions, room temperature (23±1) oC, 3 h) oxidative degradation of hydroperoxyde-enriched soybean oil (HESO) were stabilized in the presence of spin trap N-tert-butyl-a-phenylnitrone (PBN) and detected by electron spin resonance (ESR) spectrometry. In both thermal and catalytic oxidation of HESO, the same hyperfine coupling parameters (aN=14.75 G and aHβ=2.80 G) confirmed the generation of PBN-OOL/-OL spin adducts. The antiradical activity (AA) of phytic acid, in the 0.076-0.30 mM concentration range, was tested by measuring its ability to inhibit the generation of PBN-OOL/-OL spin adducts during thermal and catalytic oxidation of HESO. Phytic acid did not inhibit the thermal oxidation of HESO and showed no effect in the b-carotene bleaching test (AOA). Contrary to this, phytic acid exhibited antioxidant effect on the catalytic oxidation of HESO by chelating Fe2+ ions. The mechanism of antioxidant activity was confirmed by the results of chelating activity on Fe2+ in Fe2+-ferrozine test where a dose-dependent chelating activity of phytic acid was obtained.