Antioxidant Activity of Phytic Acid in Lipid Model System

Marijana Sakač¹*, Jasna Čanadanović-Brunet², Aleksandra Mišan¹, Vesna Tumbas² and Đorđe Medić¹

¹Institute for Food Technology, University of Novi Sad, Bulevar cara Lazara 1, RS-21000 Novi Sad, Serbia
²Department of Organic Chemistry, Faculty of Technology, University of Novi Sad, Bulevar cara Lazara 1, RS-21000 Novi Sad, Serbia

Article history:
Received March 16, 2009
Accepted July 12, 2010

Key words:
phytic acid, lipid oxyradicals, antioxidant activity, ESR, chelating activity

Summary:
Free radicals formed during thermal (60 °C, 24 h) and catalytic (Fe²⁺ ions, room temperature (23±1) °C, 3 h) oxidative degradation of hydroperoxyde-enriched soybean oil (HESO) were stabilized in the presence of spin trap N-tert-butyl-α-phenylnitrone (PBN) and detected by electron spin resonance (ESR) spectrometry. In both thermal and catalytic oxidation of HESO, the same hyperfine coupling parameters (a_N=14.75 G and a_H^β=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 β-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.

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