- Mechanistic studies of hydrogen-peroxide-mediated anthocyanin oxidation
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The oxidation of cyanidin-3-O-glucoside by hydrogen peroxide was investigated in a range of solvents. The reaction products had chemical structures identical to those formed by the reaction of this compound with the alkylperoxyl radical 2,2?-azobis(2,4-dimethyl)valeronitrile. A plausible oxidation mechanism was proposed based on the obtained reaction products, and this mechanism was confirmed by HPLC–MS experiments using 18O-labeled reagents. Further, the reaction conditions were found to influence both the reaction rate and the products formed during the transformation, which validated the proposed mechanism.
- Satake, Ryuya,Yanase, Emiko
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- Novel oxidation products of cyanidin 3-O-glucoside with 2,2′-azobis-(2,4-dimethyl)valeronitrile and evaluation of anthocyanin content and its oxidation in black rice
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The radical oxidation mechanism of anthocyanin derivatives was investigated by the reaction of cyanidin 3-O-glucoside in the presence of radical initiator 2,2′-azobis-(2,4-dimethyl)valeronitrile (AMVN) in EtOH and aqueous CH 3CN. Six different oxidation products were isolated, depending on the solvent employed. These products were identified using NMR spectroscopy and multistep derivatisation reactions. Of the products obtained, two novel oxidised anthocyanin derivatives were isolated from black rice under prolonged storage. A radical reaction mechanism is proposed on the basis of these reaction products. Quantification of oxidised anthocyanins in black rice is demonstrated as a method to verify freshness of the rice.
- Kamiya, Haruna,Yanase, Emiko,Nakatsuka, Shin-Ichi
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p. 221 - 226
(2014/03/21)
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