Fractionation of phenolic compounds from a purple corn extract and evaluation of antioxidant and antimutagenic activities
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.