title: Kinetics of the oxidation of quercetin by 2,2-diphenyl-1-picrylhydrazyl (dpph•).
abstract: In methanol/water, dpph(•) bleaching (519 nm) by quercetin, QH(2), exhibits biphasic kinetics. The dpph(•) reacts completely with the quercetin anion within 100 ms. Subsequent slower bleaching involves solvent and QH(2) addition to quinoid products. The fast reaction is first-order in dpph(•) but only ca. 0.38 order in [QH(2)]. This extraordinary nonintegral order is attributed to reversible formation of π-stacked {QH(-)/dpph(•)} complexes in which electron transfer to products, {QH(•)/dpph(-)}, is slow (k(ET) ≈ 10(5) s(-1)).
authors.affiliation: Istituto di Chimica Biomolecolare del CNR, Via P. Gaifami 18, I-95126 Catania, Italy. mario.foti@icb.cnr.it
authors.forename: Mario C
authors.initials: MC
authors.lastname: Foti
authors.forename: Carmelo
authors.initials: C
authors.lastname: Daquino
authors.forename: Gino A
authors.initials: GA
authors.lastname: DiLabio
authors.forename: K U
authors.initials: KU
authors.lastname: Ingold
mesh_terms: D001713:Biphenyl Compounds / Q000737:chemistry*; D007700:Kinetics; D000432:Methanol / Q000737:chemistry; D008958:Models, Molecular; D015394:Molecular Structure; D010084:Oxidation-Reduction; D010851:Picrates / Q000737:chemistry*; D011794:Quercetin / Q000737:chemistry*; D013237:Stereoisomerism; D014867:Water / Q000737:chemistry
chemical_list: D001713:Biphenyl Compounds; D010851:Picrates; D014867:Water; D011794:Quercetin; C004931:1,1-diphenyl-2-picrylhydrazyl; D000432:Methanol