Flavonols with a catechol or pyrogallol substitution pattern on ring B readily form stable dimers in phosphate...

Phosphate buffered saline (PBS) is a commonly used buffer in biological research. Herein, the stability of a series of flavonoids, i.e. myricetin, kaempferol, baicalein, luteolin and quercetin, were assessed in PBS within 5 s. Apigenin proved very stable in PBS and was therefore used as a control. Kaempferol and baicalein were less stable with small amounts of oxidized and hydroxylated products being detected. The other flavonoids were unstable and their dimers were identified in PBS at 4 °C under normal atmospheric conditions. Flavonols with a catechol or pyrogallol substitution pattern on ring B readily formed stable dimers and oxidized products in PBS (pH = 7.4) at 4 °C within 5 s. The chosen experimental conditions improved the stability of dimers and allowed their detection.