Abstract
Flavonoids are common polyphenolic compounds widely distributed in fruits and vegetables. These pigments have important pharmacological relevance because emerging research suggests possible anti-cancer and anti-inflammatory properties as well other beneficial health effects. These compounds are relatively hydrophobic molecules, suggesting the role of blood transport proteins in their delivery to tissues. In this study, we assess the binding interactions of four flavonoids (kaempferol, luteolin, quercetin, and resveratrol) with human serum albumin (HSA), the most abundant protein in the blood, and with glutathione S-transferase pi isoform-1 (GSTP1), an enzyme with well-characterized hydrophobic binding sites that plays an important role in detoxification of xenobiotics with reduced glutathione, using a novel Taylor dispersion surface plasmon resonance (SPR) technique. For the first time, HSA sites revealed a high-affinity binding site for flavonoid interactions. Out of the four flavonoids that we examined, quercetin and kaempferol showed the strongest equilibrium binding affinities (KD) of 63 ± 0.03 nM and 37 ± 0.07 nM, respectively. GSTP1 displayed lower affinities in the micromolar range towards all of the flavonoids tested. The interactions of flavonoids with HSA and GSTP1 were studied successfully using this novel SPR assay method. The new method is compatible with both kinetic and equilibrium analyses.
Highlights
Flavonoids are a group of plant-derived secondary metabolites
Dietary flavonoids have received increased attention, as they may potentially serve a protective role against a variety of diseases, such as cardiovascular diseases and certain cancers [2,3,4], and many researchers have been interested in their potential protective roles against major eye diseases
One recent study has shown the protective effect of resveratrol by the inhibition of vascular endothelial growth factor (VEGF) secretion, a major angiogenesis signal protein that is a key mediator of the neovascular form of age-related macular degeneration (AMD) [5]
Summary
Flavonoids are a group of plant-derived secondary metabolites. They are the most common group of polyphenolic compounds present in the human diet. GST proteins have become important targets for development of inhibitors against metabolism of chemotherapeutic drugs These enzymes are overexpressed in tumor cells, potentially resulting in multidrug resistance, and Zanden et al have reported an inhibitory effect of quercetin towards. One-shot kinetics and kinetic titration methods have been reported [16,17], but even these methods have limitations including ligand denaturation due to long injection time and frequent regenerations, injection volume variations, and sample evaporation losses, which could result in poor data quality [15] In this investigation, we have used an optimized Taylor dispersion SPR technique that can provide improved data output by reducing the systematic errors in standard injection methods
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