Kinetic Study of the Quenching Reaction of Singlet Oxygen by Eight Vegetable Oils in Solution

Abstract

INTRODUCTION Recently, reactive oxygen species ROS have attracted significant attention, because oxidative stress generated by ROS induces various disorders and diseases 1. Singlet oxygen 1 O 2 and lipid peroxyl radical LOO are wellknown representative ROS species generated in biological systems. 1 O 2 reacts with many biological targets including lipids 2 , proteins 3 , and DNA 4, 5 , as well as the peroxyl radical does. Reactions with 1 O 2 occur mainly by chemical reaction, inducing the degradation of biological systems. Carotenoids and vitamin E homologues α-, β-, γ-, δ-tocopherols-Tocs and-tocotrienols-Toc-3s are widely present in vegetables, fruits, and edible oils 6 11 and may function as efficient 1 O 2 quenchers in biological systems 12 14. Recently, kinetic studies of the quenching reaction of 1 O 2 with natural antioxidants AOs such as carotenoids, vitamin E homologues, and polyphenols were performed in

Kinetic Study of Singlet-Oxygen Quenching and Aroxyl-Radical Scavenging Activities of Vitamin E Homologs and Fatty Acids Present in Vegetable Oils

“…Recently, measurements of the singlet-oxygen 1 O 2 quenching and aroxyl-radical ArO scavenging rate constants k Q and k S , respectively of eight vegetable oils 1 -8 were performed in ethanol/chloroform/D 2 O solution 29,30 . Further, the k Q and k S values and concentrations of four tocopherols and four tocotrienols contained in the vegetable oils were measured.…”

“…Third, comparison of the k Q S Obsd. values observed for the above oils 1 -8 with the sum of the product ∑ k Q Acid-i S Acid-i /10 2 of the k Q Acid-i S value obtained for each fatty acid Acid-i and the concentration Acid-i /10 2 g/100 g unit of Acid-i contained in oils 1 -8 was performed, in order to evaluate the contribution of fatty acids 1 -9 to the 1 O 2 -quenching activity 30 . Furthermore, measurements of the ArO -scavenging rate constant k S were performed for fatty acid esters I -IV.…”

“…Further, the total k Q Total Calcd. values i.e., the sum of As reported in a previous study, measurements of UV-Vis absorption spectra were performed for vegetable oils 1 -8 30 . Perilla oil 3 exhibits a UV-vis absorption at 370 520 nm, suggesting that carotenoids are contained in oil 3 14,23 .…”

“…As reported in a previous study, measurements of the UV-Vis absorption spectra were performed for vegetable oils 1 -8 30 . The result indicates that numerous types of phenolic AOs such as γ-oryzanol, polyphenol, sesamol, and sesamine are contained in oils 1 -8.…”

“…In a previous study, the 1 O 2 -quenching rates k Q and the SOAC values were measured for eight vegetable oils numbered 1 -8 in mixed solvent via UV-vis spectrophotometry 30 . The k Q Oil S Obsd.…”