Determination of singlet oxygen quenching rate and mechanism of γ-oryzanol

Abstract

Photooxidation is one of the causes of quality deterioration in food. An antioxidant or singlet oxygen quencher is urgently needed to prevent photooxidation. γ-Oryzanol was recognized as a naturally present antioxidant in rice bran products. This research aimed to calculate the singlet oxygen quenching rate and its mechanism of γ-oryzanol to evaluate the potency of γ-oryzanol as singlet oxygen quencher. A series of linoleic acid (50 and 100 mM) or γ-oryzanol (0.7 and 1.5 mM) were prepared separately in ethanol: chloroform (96:4, v/v) containing 25 ppm of erythrosine. High-Performance Liquid Chromatography quantified the degradation of γ-oryzanol. Meanwhile, Gas Chromatography determined the changes in linoleic acid content during photooxidation. The singlet oxygen quenching rate was calculated by steady-state. The singlet oxygen quenching rate of γ-oryzanol was 3.04 Â 10 6 / M/s by physical and chemical quenching mechanism. Photooxidation caused the declined of γ-oryzanol by 0.1421 mM/h. Based on singlet oxygen quenching rate calculation, it suggests that γ-oryzanol can perform as a singlet oxygen quencher with slightly dominated by physical quenching mechanism (52.28%). The rest it performed via a chemical quenching mechanism.

Kinetics of Squalene Quenching Singlet Oxygen and the Thermal Degradation Products Identification

“…The adopted singlet oxygen decaying rate in ethanol, as reported by previous studies, was used as a reference for k d (k d = 8.30 × 10 4 ). 33 The impact of different concentrations of squalene on the oxidation of α-terpinene in ethanol containing methylene blue during a time course of light exposure (Figure 1A). The results indicate that squalene inhibiting the oxidation of α-terpinene in an ethanol solution containing methylene blue was concentration dependent.…”

“…[SQ] is the concentration of squalene. The adopted singlet oxygen decaying rate in ethanol, as reported by previous studies, was used as a reference for k d ( k d = 8.30 × 10 4 ) …”