['Intestinal cells are constantly exposed to luminal toxins. In this study, we investigated the effect of cellular stress caused by valinomycin, which is structurally and functionally similar to the bacterial toxin cereulide, on quercetin metabolism and cellular localization in undifferentiated cells.', 'Coadministration of quercetin and valinomycin (50 μM quercetin/0.05 μM valinomycin) reduced intracellular reactive oxygen species content and increased cell viability (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide) of Caco-2 cells compared to valinomycin-only (0.05 μM) treatment. Quercertin was effectively metabolized into methyl, glucuronide, and sulfate conjugates, which were mostly secreted into to the culture medium. Three different O-methylated quercetin isomers were detected. Two were exported from the cells and one remained intracellularly. Further, valinomycin caused an increase in the intracellular accumulation of O-methylated quercetin metabolites compared to cells treated only with quercetin. In valinomycin-untreated cells, quercetin and O-methylated quercetin metabolite were localized in the cell membrane, whereas valinomycin treatment resulted in their uptake by the cells.'] Does quercetin mitigate valinomycin-induced cellular stress via stress-induced metabolism and cell uptake?