Influences of Glucose on the Dietary Hydroxyflavonoid–Plasma Protein Interaction

The influence of glucose on the interaction between flavonoids and plasma proteins from healthy humans (HPPs) was investigated. Glucose affected the flavonoid-protein interactions depending upon their structures. Glucose significantly reduced the affinities of HPPs for 6-hydroxyflavone by 10.72 times, slightly weakened the affinities of HPPs for quercetin, 7-hydroxyflavone, and kaempferol, and hardly affected the affinities of HPPs for myricetin, chrysin, and 3,7-dihydroxyflavone on the first day. However, glucose obviously enhanced the affinities of HPPs for 3-hydroxyflavone, luteolin, and apigenin. Glucose significantly weakened the binding affinities of HPPs for chrysin, kaempferol, quercetin, and myricetin by 6.17, 7.94, 14.12, and 112.2 times, when kept at 37 °C under air conditions for 14 days, and the binding affinities of HPPs for 7-hydroxyflavone, luteolin, 3,7-dihydroxyflavone, 3-hydroxyflavone, and 6-hydroxyflavone were slightly decreased by 1.35-, 1.58-, 1.58-, 1.9-, and 2.4-fold. The binding affinity between apigenin and HPP was hardly influenced. Glucose weakened the binding affinities of HPPs for hydroxyflavonoids. The differences between log K(a)(absence) and log K(a)(presence) were bigger for the more lipophilic hydroxyflavonoids, and more lipophilic hydroxyflavonoids are easily affected by glucose, when kept at 37 °C under air conditions for 14 days. These flavonoids with lower hydrogen donor/acceptor numbers prefer to stably interact with HPPs in the presence of glucose. However, other flavonoids with high hydrogen donor/acceptor numbers (multi-hydroxyl flavonoids) were apt to reduce their affinities with HPPs in the presence of glucose.