Oxidation of caffeic acid in fruit juice-like model solutions containing L-Cysteine: isolation of 2-S-Cysteinylcaffeic acid and evaluation of its antioxidant properties
2002
Bassil, D.
Hydroxycinnamates are phenylpropanoid metabolites that occur widely in edible plants and plant products such as wine, tea and coffee. There is an increasing awareness that hydroxycinnamates and their conjugates are bioctive plant food ingredients that posses potent in vitro antioxidant activity that might have a beneficial health in vivo on health. Caffeic acid (3,4-dihydroxycinnamic acid) has been shown to be and alpha-tocopherol protectant in LDL, while caffeic acid conjugates, such as chlorogenic (caffeoylquinic) and caftaric (caffeoyltraric) acids, have been to be demonstrated more powerful antioxidants in a number of different systems. Caffeic acid and its derivatives are good substrates of polyphenol oxidases and, under certain condtions, may undergo oxidation in plant tissues or in products of plant origin, giving an array of products. However, caffeic acid, due to its o-diphenol feature, is also prone to oxidation by dioxygen (autoxidation) and other biologically relevant oxidants, such as peroxynitrile. The oxidation of caffeic accid, but also of other structurally similar components, has been show to proceed via formation of o-quinones, which may be spontaneously react yielded. The oxidation of caffeic acid (3,4-dihydroxycinnamic acid) was performed in sodium periodate solutions (pH 3.5) on a small scale, and in 50
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