Title:Dependence of DPPH Radical Scavenging Activity of Dietary Flavonoid Quercetin on Reaction Environment
Volume: 14
Issue: 6
Author(s): Katrin Sak
Affiliation:
Keywords:
Antioxidant capacity, oxidative stress, phytochemicals, polyphenols, redox balance.
Abstract: Many of nowadays diseases are due to the oxidative stress resulting from imbalance between formation and
neutralization of free radicals. Intake of dietary antioxidants is therefore crucial to maintain good health. As the safety of
synthetic antioxidants has raised several questions the search for natural efficient antioxidants from chemicals produced
by plants has gained increased popularity in recent years. Quercetin is an abundant dietary flavonoid with well-known
radical scavenging properties being often used as a reference compound in many antioxidant tests. Its reaction with 1,1-
diphenyl-2-picrylhydrazyl (artificial DPPH radical) is rapid and stoichiometric; however the published inhibitory
constants vary in a very wide range, from 95 nM to 226 µM. The analysis indicates the dependence of antiradical capacity
of quercetin on the composition of solvent systems where the reactions are performed and also on the surrounding
temperature showing somewhat higher scavenging ability at body temperature compared to room conditions. At the same
time, this activity is generally independent on the initial DPPH concentration. These data highlight the importance to
consider the reaction environment and conditions when predicting the redox behavior of quercetin in a certain cellular
context. Moreover, due to the changes in cellular environment accompanying with different pathogeneses the redox action
of polyphenols can essentially vary leading even to the situations where the well-known antioxidant quercetin may reveal
prooxidant properties.
