Changes of the stability and bioactivity of quercetin and myricetin in BGC-823 cells in response to heat treatment and Fe2+/Cu2+ addition

Abstract

Two flavonols quercetin and myricetin with heat treatment and Fe2+/Cu2+ addition were assessed for stability and bioactivity changes. Quercetin and myricetin at 37 °C showed higher degradation rate constants than those at 20 °C (0.133 − 1.025 vs. 0.299 − 1.803 h−1). Due to the chelation of flavonol and metals, Fe/Cu addition at the two temperatures (except Cu addition at 37 °C) mostly led to enhanced stability via decreasing the constant values to 0.064 − 0.675 h−1. Cell counting kit-8 assaying results showed that myricetin and quercetin heated at 37 °C and 100 °C received decreased growth inhibition in human gastric cancer BGC-823 cells, because they at 80 μmol/L showed decreased inhibition percentages (from 41.1 − 45.6 to 23.9 − 43.3%, cell treatment of 24 h; or from 46.6 − 51.9 to 28.8 − 46.5%, cell treatment of 48 h). The assaying results of Hoechst 33,258staining, DCFH-DA fluorescence probe, and flow cytometry also proved that the heated flavonols in the cells had less reactive oxygen species generation, lower DNA damage, and weakened apoptosis induction, compared with the unheated flavonols. Fe addition decreased these flavonol bioactivities in the cells because of decreased flavonol–Fe chelation and enhanced flavonol degradation; however, Cu addition induced oxidative stress and thus led to less bioactivity decrease than Fe addition. Correlation analysis results indicated that decreased reactive oxygen species generation of the two flavonols was correlated with decreased apoptosis induction (p < 0.05). Overall, these used treatments brought about stability and bioactivity changes for the two flavonols, suggesting reasonable consideration should be paid on processing conditions and some components of foods when studying food bioactivities.