DPPH (=2,2-diphenyl-1-picrylhydrazyl=2,2-diphenyl-1-(2,4,6-trinitrophenyl)hydrazyl) radical-scavenging reaction of protocatechuic acid esters (=3,4-dihydroxybenzoates) in alcohols : Formation of bis-alcohol adduct

スポンサーリンク

概要

• 論文の詳細を見る

• Protocatechuic acid esters (=3,4-dihydroxybenzoates) scavenge ca. 5 equiv. of radical in alcoholic solvents. whereas they consume only 2 equiv. of radical in nonalcoholic solvents. While the high radical-scavenging activity of protocatechuic acid esters in alcoholic solvents as compared to that in nonalcoholic solvents is due to a nucleophilic addition of an alcohol molecule at C(2) of an intermediate o-quinone structure, thus regenerating a catechol (=benzene-1,2-diol) structure, it is still unclear why protocatechuic acid esters scavenge more than 4 equiv. of radical (C(2) refers to the protocatechuic acid numbering). Therefore, to elucidate the oxidation mechanism beyond the formation of the C(2) alcohol adduct, 3,4-dihydroxy-2-methoxybenzoic acid methyl ester (4), the C(2) MeOH adduct, which is ail oxidation product of methyl protocatechuate (1) in MeOH, was oxidized by the DPPH radical (=2,2diphenyl-1-picrylhydrazyl) or o-chloranil (=3 4,5,6-tetrachlorocyclohexa-35-diene-1,2-dione) in CD3- OD/(D-6)acetone 3: 1). The oxidation mixtures were directly analyzed by NMR. Oxidation with both the DPPH radical and o-chloranil produced a C(2),C(6) bis-methanol adduct (7), which could scavenge additional 2 equiv. of radical. Calculations of LUMO electron densities of o-quinones corroborated the regioselective nucleophilic addition of alcohol molecules with o-quinones. Our results strongly suggest that the regeneration of a catechol structure via a nucleophilic addition of ail alcohol molecule with a o-quinone is a key reaction for the high radical-scavenging activity of protocatechuic acid esters in alcoholic solvents.

• 2006-04-19

著者

• 齊藤 静夏

  北大院薬

• Gao Hong

  Division of Applied Bioscience, Graduate School of Agriculture, Hokkaido University

• Kawabata Jun

  北海道大学 大学院農学研究院応用生命科学部門

• Gao Hong

  北海道大学 大学院農学研究院応用生命科学部門

• Saito Shizuka

  Lab. Of Food Biochemistry Div. Of Applied Bioscience Graduate School Of Agriculture Hokkaido Univ.

• Saito Shizuka

  Laboratory Of Food Biochemistry Division Of Applied Bioscience Graduate School Of Agriculture Hokkai

• Gao Hong

  Division Of Applied Bioscience Graduate School Of Agriculture Hokkaido University

• Kawabata Jun

  Division Of Applied Bioscience Graduate School Of Agriculture Hokkaido University

• Saito Shizuka

  Laboratory Of Food Biochemistry Division Of Applied Bioscience Graduate School Of Agriculture Hokkai

関連論文

• P-11 ユズリハ科植物由来の新規アルカロイドcalyciphylline C〜Gの構造と生物活性(ポスター発表の部)
• DPPH (=2,2-diphenyl-1-picrylhydrazyl=2,2-diphenyl-1-(2,4,6-trinitrophenyl)hydrazyl) radical-scavenging reaction of protocatechuic acid esters (=3,4-dihydroxybenzoates) in alcohols : Formation of bis-alcohol adduct
• Chebulagic Acid Is a Potent α-Glucosidase Inhibitor
• カテコール型ポリフェノールのラジカル消去活性増大機構 : キノン体生成以降の反応経路が判明
• Inhibitory Effects of 5,6,7-Trihydroxyflavones on Tyrosinase
• Effects of Alcoholic Solvent on Antiradical Abilities of Protocatechuic Acid and Its Alkyl Esters
• Quinone Hemiacetal Formation from Protocatechuic Acid during the DPPH Radical Scavenging Reaction(Organic Chemistry)
• A Novel Oxidative Dimer from Protocatechuic Esters : Contribution to the Total Radical Scavenging Ability of Protocatechuic Esters
• Chebulagic Acid Is a Potent α-Glucosidase Inhibitor

スポンサーリンク