Temperature-dependence of radical-trapping activity of phenoxazine, phenothiazine and their aza-analogues clarifies the way forward for new antioxidant design.

ABSTRACT: The prediction and/or rationalization of diarylamine radical-trapping antioxidant (RTA) activity at the elevated temperatures where they are most useful presents a significant challenge, precluding the development of new technology. Whilst structure-activity relationships at ambient temperatures are well established, their predictive capacity at elevated temperatures is poor due to competing reactions. A striking example involves phenoxazine, which is a superior RTA relative to its sulfur analog phenothiazine at ambient temperature (e.g. k = 3.9 × 10⁷ vs. 7.6 × 10⁶ M^-1 s^-1 at 37 °C, respectively), but is demonstrably inferior at elevated temperatures. Despite being inherently less oxidizable in electrochemical experiments and high-a

SUBMITTER: Poon JF 

PROVIDER: S-EPMC8386644 | biostudies-literature | 2021 Aug

REPOSITORIES: biostudies-literature