title: Astaxanthin diferulate as a bifunctional antioxidant.
abstract: Astaxanthin when esterified with ferulic acid is better singlet oxygen quencher with k2 = (1.58 ± 0.1) 10(10) L mol(-1)s(-1) in ethanol at 25°C compared with astaxanthin with k2 = (1.12 ± 0.01) 10(9) L mol(-1)s(-1). The ferulate moiety in the astaxanthin diester is a better radical scavenger than free ferulic acid as seen from the rate constant of scavenging of 1-hydroxyethyl radicals in ethanol at 25°C with a second-order rate constant of (1.68 ± 0.1) 10(8) L mol(-1)s(-1) compared with (1.60 ± 0.03) 10(7) L mol(-1)s(-1) for the astaxanthin:ferulic acid mixture, 1:2 equivalents. The mutual enhancement of antioxidant activity for the newly synthetized astaxanthin diferulate becoming a bifunctional antioxidant is rationalized according to a two-dimensional classification plot for electron donation and electron acceptance capability.
authors.affiliation: Chemistry Institute of São Carlos, University of São Paulo , Av. Trabalhador São Carlense 400, São Carlos - SP , Brazil.
authors.forename: T B R
authors.initials: TB
authors.lastname: Papa
authors.forename: V D
authors.initials: VD
authors.lastname: Pinho
authors.forename: E S P
authors.initials: ES
authors.lastname: do Nascimento
authors.forename: W G
authors.initials: WG
authors.lastname: Santos
authors.forename: A C B
authors.initials: AC
authors.lastname: Burtoloso
authors.forename: L H
authors.initials: LH
authors.lastname: Skibsted
authors.forename: D R
authors.initials: DR
authors.lastname: Cardoso
mesh_terms: D000975:Antioxidants / Q000138:chemical synthesis / Q000737:chemistry* / Q000494:pharmacology*; D002338:Carotenoids / Q000737:chemistry; D003373:Coumaric Acids / Q000737:chemistry / Q000494:pharmacology; D010084:Oxidation-Reduction; D018384:Oxidative Stress; D024341:Xanthophylls / Q000138:chemical synthesis / Q000737:chemistry / Q000494:pharmacology
chemical_list: D000975:Antioxidants; D003373:Coumaric Acids; D024341:Xanthophylls; D002338:Carotenoids; C005948:astaxanthine; C004999:ferulic acid
keywords: antioxidant; antiradical; astaxanthin; carotenoid; plant phenol