Antioxidation Mechanism Studies of Caffeic Acid: Identification of Antioxidation Products of Methyl Caffeate from Lipid Oxidation

Abstract

As a part of a research project on the elucidation of the chain-breaking antioxidation mechanism of natural phenols in food components, caffeic acid, a polyphenolic acid widely distributed in edible plants, was investigated. The identification and time course analysis of the antioxidation reaction products from methyl caffeate were carried out in the ethyl linoleate oxidation system. The antioxidation reaction produced a quinone derivative of methyl caffeate as an antioxidation product during the initial stage, which was identified by (13)C NMR. The quinone, however, was not the final product, and a further reaction occurred to produce several new peroxides. The isolation and structure determination of the peroxides revealed that they had tricyclic structures, which consisted of ethyl linoleate, methyl caffeate, and molecular oxygen. On the basis of the formation pathway of these products, an antioxidation reaction mechanism of methyl caffeate, including the redox reaction of the caffeate and Diels-Alder reaction of the produced peroxides, was proposed.

Antimicrobial and antioxidant properties of phenolic acids alkyl esters

“…Gentisic acid exhibited approximately doubled PF, whereas its ester forms exhibited considerably low PF as a result of losing their antioxidant properties. Masuda et al (2008) described the antioxidant mechanisms of polyphenols (caffeic acid) as quinone form of dihydroxylbenzene that is much more easily oxidisable than the biological material.…”

Induction of caspase-dependent apoptosis in melanoma cells by the synthetic compound (E)-1-(3,4-dihydroxyphenethyl)-3-styrylurea

“…Specifically, caffeic acid, ferulic acid and p-coumaric acid are found to produce various beneficial effects, including anti-oxidation (7,8), anti-inflammation (9), cancer chemoprevention (10) and anti-melanogenesis (6). Other findings suggest that phenolic acids containing aromatic hydroxyl groups have great potential for use in biological and pharmacological applications, a result derived from their anti-oxidant activities.…”

Identification of the Antioxidation Reaction Products from a Sinapic Ester in a Lipid Oxidation System

“…During our studies on the reaction mechanism for the antioxidation of phenolic acids, 5,6) we found similar tricyclic compounds, which had been produced by radical oxidation coupling and the subsequent intramolecular Diels-Alder reaction between phenolic acid and linoleate, in the lipid oxidation system as the main antioxidation products. Although the antioxidant activity of phenolic acid varies due to the substituted pattern on the benzene ring, 8) the formation pathway for a tricyclic product, which may be more stable than a simple phenolic acid-lipid peroxide, should represent an important and essential antioxidation reaction mechanism for phenolic acid antioxidants.…”

“…[2][3][4][5][6] Sinapic acid (1), 4-hydroxy-3,5-dimethoxycinnamic acid, is one of the phenolic acids widely distributed in such edible plants as cereals, nuts, oil seeds, and berries. 7) Rapeseed particularly contains sinapic acid as the predominant phenol.…”