Flavonoid binding to human serum albumin.

Area of Science:

• Biochemistry
• Pharmacology
• Nutritional Science

Background:

• Dietary flavonoids show promise in preventing chronic diseases.
• Poor bioavailability of flavonoids may stem from interactions with plasma proteins like human serum albumin (HSA).

Purpose of the Study:

• To assess the binding affinity of key flavonoids (daidzein, genistein, naringenin, quercetin) and their metabolites to HSA.
• To investigate the effect of oleate, a fatty acid, on flavonoid-HSA interactions.

Main Methods:

• Determined dissociation equilibrium constants (K) for flavonoid binding to Sudlow's site I on HSA.
• Performed binding assays in the absence and presence of saturating oleate concentrations at pH 7.0 and 20.0°C.

Main Results:

• Flavonoids exhibited significant binding affinity to HSA, with K values ranging from 3.3x10⁻⁶ to 3.9x10⁻⁵ M.
• The presence of oleate approximately doubled the K values, indicating a two-fold decrease in flavonoid affinity for HSA.
• These findings suggest fatty acids act as allosteric inhibitors of flavonoid binding.

Conclusions:

• Flavonoids are primarily bound to human serum albumin in vivo.
• Fatty acids, such as oleate, can allosterically inhibit flavonoid bioavailability by reducing their binding to HSA.
• Understanding these interactions is crucial for predicting the efficacy of dietary compounds, supplements, and drug interactions.