Antioxidant mechanisms of polyphenolic caffeic acid oligomers, constituents of Salvia officinalis

作者：Bors W^*; Michel C; Stettmaier K; Lu YR; Foo LY

来源：Biological Research, 2004, 37(2): 301-311.

DOI：10.4067/s0716-97602004000200017

• Caffeic acid oligomer
• catechol semiquinone
• electron paramagnetic resonance
• hydroxyl radical
• kinetic modeling
• pulse radiolysis
• Salvia officinalis

Caffeic acid, rosmarinic acid and oligomers of caffeic acid with multiple catechol groups are all constituents of Salvia officinalis. Their antioxidant potential was investigated with regard to their radical scavenging activity and the stability and structure of the intermediate radicals. Pulse-radiolytic studies revealed very high rate constants with hydroxyl radicals. Evidence from kinetic modeling calculations suggested an unusual complex behavior due to the presence of both O-4- and O-3-semiquinones and formation and decay of a hydroxyl radical adduct at the vinyl side chain. The radical structures observed by EPR spectroscopy after autoxidation in slightly alkaline solutions were only partially identified due to their instability and generally represented dissociated O-4-semiquinones. Hybrid density-functional calculations of the potential radical structures showed distinct differences between the resonance stabilization of the O-4- and O-3-semiquinones of caffeic and dihydrocaffeic acids. reflected also in the considerably faster decay of the O-3-semiquinone observed by pulse radiolysis. No evidence was found for dimerization reactions via Cbeta radicals typical for lignin biosynthesis.

• 出版日期2004