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 °C, and analysed for antiradical activity by the DPPH assay. tial 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.