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  • Title: Mechanisms of flavonoid repair reactions with amino acid radicals in models of biological systems: a pulse radiolysis study in micelles and human serum albumin.
    Author: Filipe P, Morlière P, Patterson LK, Hug GL, Mazière JC, Mazière C, Freitas JP, Fernandes A, Santus R.
    Journal: Biochim Biophys Acta; 2002 Jun 06; 1571(2):102-14. PubMed ID: 12049790.
    Abstract:
    Neutral tryptophan (*Trp) and tyrosine (TyrO(*)) radicals are repaired by certain flavonoids in buffer, in micelles and in human serum albumin (HSA) with corresponding formation of semioxidized flavonoid radicals. In deaerated buffer, *Trp but not TyrO(*) radicals react with catechin. In micelles, quercetin and rutin repair both *Trp and TyrO(*) radicals. In addition to amino acid reactivity, microenvironmental factors and nature of the flavonoids govern this repair. Electron transfer efficiencies from quercetin to negatively charged *Trp radicals are 100% in the micellar pseudophases of positively charged cetyltrimethylammonium bromide, (CTAB), and neutral Triton X100 (TX100), but 55% in negatively charged sodium dodecyl sulfate (SDS). In oxygen-saturated CTAB micelles, quercetin also reacts with the superoxide radical anion. When bound to domain IIA of HSA, quercetin repairs, by intra- or intermolecular encounter, less than 20% of oxidative damage to HSA. Quercetin can also repair freely circulating oxidized molecules with repair efficiencies falling to 7% for oxidized *Trp, Tyr and alpha-MSH and to less than 2% for urate radical. This limited effectiveness is attributed both to the inaccessibility of bound quercetin and rutin toward radicals of circulating molecules and to the diffusion-controlled recombination of these radicals.
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