Measurements of the singlet oxygen ( 1 O 2 ) quenching rates (k Q (S)) and the relative singlet oxygen absorption capacity (SOAC) values were performed for 11 antioxidants (AOs) (eight vitamin E homologues (α-, β-, γ-, and δ-tocopherols and -tocotrienols (-Tocs and -Toc-3s)), two vitamin E metabolites (α-and γ-carboxyethyl-6-hydroxychroman), and trolox) in ethanol/chloroform/D 2 O (50:50:1, v/v/v) and ethanol solutions at 35°C. Similar measurements were performed for five palm oil extracts 1-5 and one soybean extract 6, which included different concentrations of Tocs, Toc-3s, and carotenoids. Furthermore, the concentrations (wt%) of Tocs, Toc-3s, and carotenoids included in extracts 1-6 were determined. From the results, it has been clarified that the 1 O 2 -quenching rates (k Q (S)) (that is, the relative SOAC value) obtained for extracts 1-6 may be explained as the sum of the product {Σ k Q AO-i (S) [AO-i]/100} of the rate constant (k Q AO-i (S)) and the concentration ([AO-i]/100) of AO-i (Tocs, Toc-3s, and carotenoid) included.