Reevaluation of Physical and Chemical Singlet Oxygen Quenching Efficiency of Antioxidants via a Specific...

Furfuryl alcohol (FFA), a methanol-soluble and highly specific compound for singlet oxygen (¹O₂), was used as a ¹O₂ trapping agent to reevaluate physical and chemical ¹O₂ quenching efficiency of five antioxidants, namely α-tocopherol, butylated hydroxyanisole (BHA), tert-butylhydroquinone (TBHQ), epigallocatechin gallate (EGCG), and quercetin. The total ¹O₂ quenching 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) × 10⁸ M^-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 × 10⁶ M^-1s^-1, respectively. The percentages of chemical quenching in total ¹O₂ quenching 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 quenched ¹O₂ almost exclusively by a physical quenching mechanism. This is the first report on the ¹O₂ quenching 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.