Solvent effect on quercetin antioxidant capacity

In this work, a study of the evolution of antioxidant activity during quercetin degradation under different solvent and temperature conditions is undertaken. In particular, quercetin solutions in ethanol, methanol or water-ethanol mixture were stored at 22, 37 and 60 degreesC, and analysed for antiradical activity by the DPPH. assay. An initial increase and a following decrease in antiradical activity were observed for quercetin solutions in ethanol and methanol. Maximum antioxidant activity was higher and occurs in a shorter time as storage temperature was increased or solvent polarity was decreased. By contrast, a progressive decrease in antioxidant activity was observed in quercetin hydro-alcoholic solutions. Differences in antioxidant activity evolution were attributed to the development of selected reaction pathways: polymerisation was the prevalent oxidative reaction pool in ethanol or methanol solutions, whilst oxidative cleavage was favoured in hydro-alcoholic ones. (C) 2004 Elsevier Ltd. All rights reserved.