Kinetic study of aroxyl radical scavenging and α-tocopheroxyl regeneration rates of pyrroloquinolinequinol (PQQH2, a reduced form of pyrroloquinolinequinone) in dimethyl sulfoxide solution: finding of synergistic effect on the reaction rate due to the coexistence of α-tocopherol and PQQH2.
J Agric Food Chem
; 61(46): 11048-60, 2013 Nov 20.
Article
em En
| MEDLINE
| ID: mdl-24175624
ABSTRACT
Measurements of aroxyl radical (ArOâ¢)-scavenging rate constants (ks AOH) of antioxidants (AOHs pyrroloquinolinequinol (PQQH2), α-tocopherol (α-TocH), ubiquinol-10 (UQ10H2), epicatechin, epigallocatechin, epigallocatechin gallate, and caffeic acid) were performed in dimethyl sulfoxide (DMSO) solution, using stopped-flow spectrophotometry. The ks AOH values were measured not only for each AOH but also for the mixtures of two AOHs ((i) α-TocH and PQQH2 and (ii) α-TocH and UQ10H2). A notable synergistic effect that the ks AOH values increase 1.72, 2.42, and 2.50 times for α-TocH, PQQH2, and UQ10H2, respectively, was observed for the solutions including two kinds of AOHs. Measurements of the regeneration rates of α-tocopheroxyl radical (α-Tocâ¢) to α-TocH by PQQH2 and UQ10H2 were performed in DMSO, using double-mixing stopped-flow spectrophotometry. Second-order rate constants (kr) obtained for PQQH2 and UQ10H2 were 1.08 × 105 and 3.57 × 104 M−1 s−1, respectively, indicating that the kr value of PQQH2 is 3.0 times larger than that of UQ10H2. It has been clarified that PQQH2 and UQ10H2 having two HO groups within a molecule may rapidly regenerate two molecules of α-Toc⢠to α-TocH. The result indicates that the prooxidant effect of α-Toc⢠is suppressed by the coexistence of PQQH2 or UQ10H2.
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Base de dados:
MEDLINE
Assunto principal:
Dimetil Sulfóxido
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Sequestradores de Radicais Livres
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Alfa-Tocoferol
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Cofator PQQ
Idioma:
En
Ano de publicação:
2013
Tipo de documento:
Article