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

Introduction In recent years, reactive oxygen species ROS have attracted much attention, because various disorders and diseases are induced by the oxidative stress generated by them 1. Singlet oxygen 1 O 2 and lipid peroxyl radical LOO are well-known representative ROS generated in biological systems. 1 O 2 and LOO react with numerous types of biological molecules such as lipids 2 5 , proteins 6 , and DNA 7, 8 , inducing the degradation of biological systems. Carotenoids and vitamin E homologs α-, β-, γ-, and δ-tocopherols-Tocs and-tocotrienols-Toc-3s are widely present in vegetables, fruits, and edible oils 9 14 and may function as antioxidants AOs by quenching 1 O 2 and/