Abstract
Chrysin (5,7-dihydroxyflavone) is a flavonoid aglycone, which is found in nature and in several dietary supplements. During the biotransformation of chrysin, its conjugated metabolites chrysin-7-sulfate (C7S) and chrysin-7-glucuronide (C7G) are formed. Despite the fact that these conjugates appear in the circulation at much higher concentrations than chrysin, their interactions with serum albumin have not been reported. In this study, the complex formation of chrysin, C7S, and C7G with human (HSA) and bovine (BSA) serum albumins was investigated employing fluorescence spectroscopic, ultrafiltration, and modeling studies. Our major observations/conclusions are as follows: (1) Compared to chrysin, C7S binds with a threefold higher affinity to HSA, while C7G binds with a threefold lower affinity; (2) the albumin-binding of chrysin, C7S, and C7G did not show any large species differences regarding HSA and BSA; (3) tested flavonoids likely occupy Sudlow’s Site I in HSA; (4) C7S causes significant displacement of Sudlow’s Site I ligands, exerting an even stronger displacing ability than the parent compound chrysin. Considering the above-listed observations, the high intake of chrysin (e.g., through the consumption of dietary supplements with high chrysin contents) may interfere with the albumin-binding of several drugs, mainly due to the strong interaction of C7S with HSA.
Highlights
Flavonoids are polyphenolic compounds, which are widely distributed in the plant kingdom
Flavonoids can exert several beneficial effects in the body [1]; they can interact with serum albumin [2,3], biotransformation enzymes [4], and transport proteins [5], leading to their ability to affect the pharmacokinetics of drugs [6]
In a concentration-dependent fashion, chrysin and its metabolites induced a significant decrease in the fluorescence emission signal of human serum albumin (HSA) at 340 nm (Figure 2, top; λex = 295 nm)
Summary
Flavonoids are polyphenolic compounds, which are widely distributed in the plant kingdom. Flavonoids can exert several beneficial effects in the body [1]; they can interact with serum albumin [2,3], biotransformation enzymes [4], and transport proteins [5], leading to their ability to affect the pharmacokinetics of drugs [6]. Chrysin and its metabolites induced very similar quenching effects on BSA compared to HSA (Figure 3). C7S binds with even greater affinity to HSA compared to chrysin, and it exerts stronger displacing ability vs Sudlow’s Site I ligands than the parent compound. Considering the above-listed observations, a high intake of chrysin may interfere with the albumin-binding of some drugs, mainly due to the strong interaction of C7S with HSA
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