Quercetin increases stress resistance in the yeast Saccharomyces cerevisiae not only as an antioxidant

Quercetin is one of the most abundant dietary flavonoids and one of the most studied antioxidants. In this work, the effect of quercetin on stress resistance of exponentially growing Saccharomyces cerevisiae cells was estimated. Pre-treatment with low concentrations (10 μM and 100 μM) of quercetin enhanced yeast viability under exposure to hydrogen peroxide, copper ions (Cu2+), and heat shock. The stress-protective effects of quercetin were not connected with involvement of oxidative stress regulator Yap1p, or with induction of endogenous antioxidant defense. However, pre-treatment of wild type and ∆yap1 strains with quercetin prevented protein oxidation and antioxidant enzyme inactivation in yeast cells under H2O2-induced oxidative stress. Cycloheximide—an inhibitor of mRNA translation—or a deficiency in the transcriptional regulators Msn2p and Msn4p abolished the protective effects of low concentrations of quercetin against H2O2 toxicity. It was shown in vitro that quercetin can scavenge H2O2 and produce low amounts of H2O2 in a pH-dependent manner. The antioxidant-related and antioxidant-independent mechanisms of quercetin effects are discussed.