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Fractionation of phenolic compounds from a purple corn extract and evaluation of antioxidant and antimutagenic activities
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Qualitative and quantitative analysis of anthocyanins and other phenolic compounds from a purple corn extract was performed. The purple corn extract had cyanidin-3-glucoside, pelargonidin-3-glucoside, peonidin-3-glucoside and its respective acylated anthocyanin-glucosides. Cyadinin-3glucoside was the main constituent (44.4 ?? 4.7%) followed by the acylated cyanidin-3-glucoside (26.9 ?? 8.0%). Other phenolic compounds present in the purple corn corresponded to protocatechuic acid, vanillic acid, and p-coumaric acid. In addition, quercetin derivatives, a hesperitin derivative and pcoumaric and ferulic acid derivatives were found. Fractionation of phenolic compounds yielded two main fractions, an anthocyanin-rich water fraction (WF) and an ethyl acetate fraction (EAF). Evaluation of antimutagenic activity in both fractions revealed higher antimutagenic activity in the ethyl acetate fraction compared to the anthocyanin-rich fraction. On the other hand, antioxidant activity of the anthocyanin-rich fraction was higher compared to the ethyl acetate fraction. Further fractionation of the anthocyanin-rich fraction in a Toyopearl HW40 gel permeation column yielded five sub-fractions which showed no difference in antimutagenic activity except for the water sub-fraction WF-V. All the sub-fractions were active as antimutagens and antioxidants. Further fractionation of the ethyl acetate fraction yielded four sub-fractions that showed to be active as antimutagens and antioxidants. Ethyl acetate sub-fraction EAF-IV was the most active as an antimutagen. HPLC-DAD characterization of that sub-fraction revealed mainly the presence of a quercetin derivative with UV-visible spectral characteristics similar to rutin but with a little longer retention time. The mechanism of antimutagenic action by the phenolic compounds present either in the anthocyanin-rich fraction or the ethyl acetate fraction and sub-fraction EAFIV seems to be a contribution of a direct action on the enzymes involved in the activation of the mutagen and to the scavenging activity of the mutagen nucleophiles, as demonstrated by our assays.
Pedreschi, Romina Paola (2005). Fractionation of phenolic compounds from a purple corn extract and evaluation of antioxidant and antimutagenic activities. Master's thesis, Texas A&M University. Texas A&M University. Available electronically from