Reevaluation of Physical and Chemical Singlet Oxygen Quenching Efficiency of Antioxidants via a Specific Methanol-Soluble Trap

Furfuryl alcohol (FFA), a methanol-soluble and highly specific compound for singlet oxygen (1O2), was used as a1O2trapping agent to reevaluate physical and chemical1O2quenching efficiency of five antioxidants, namely α-tocopherol, butylated hydroxyanisole (BHA), tert-butylhydroquinone (TBHQ), epigallocatechin gallate (EGCG), and quercetin. The total1O2quenching rate constants of α-tocopherol, BHA, TBHQ, EGCG, and quercetin were 2.0 (±0.1) × 109, 1.1 (±0.1) × 108, 5.6 (±0.3) × 108, 4.1 (±0.1) × 108, and 2.2 (±0.1) × 108M−1s−1, respectively. The chemical quenching rate constants of α-tocopherol, BHA, TBHQ, EGCG, and quercetin were 1.4 × 107, 2.0 × 106, 7.7 × 106, 2.0 × 107, and 7.9 × 106M−1s−1, respectively. The percentages of chemical quenching in total1O2quenching were 0.7%, 1.8%, 1.4%, 4.8%, and 3.6% for α-tocopherol, BHA, TBHQ, EGCG, and quercetin, respectively, indicating that the five antioxidants quenched1O2almost exclusively by a physical quenching mechanism. This is the first report on the1O2quenching mechanism of quercetin in methanol solvent. The results of this study will provide theoretical guidance for the application of antioxidants to inhibit edible oil or fat-containing food from photooxidation.