Dufour Claire, Dangles Olivier
UMR A408 Institut National de la Recherche Agronomique, Université d'Avignon, Safety and Quality of Plant Products--Agroparc, 84914 Avignon Cedex 9, France.
Biochim Biophys Acta. 2005 Jan 18;1721(1-3):164-73. doi: 10.1016/j.bbagen.2004.10.013. Epub 2004 Nov 11.
After a meal rich in plant products, dietary flavonols can be detected in plasma as serum albumin-bound conjugates. Flavonol-albumin binding is expected to modulate the bioavailability of flavonols. In this work, the binding of structurally different flavonoids to human and bovine serum albumins is investigated by fluorescence spectroscopy using three methods: the quenching of the albumin fluorescence, the enhancement of the flavonoid fluorescence, the quenching of the fluorescence of the quercetin-albumin complex by a second flavonoid. The latter method is extended to probes whose high-affinity binding sites are known to be located in one of the two major subdomains (warfarin and dansyl-L-asparagine for subdomain IIA, ibuprofen and diazepam for subdomain IIIA). Overall, flavonoids display moderate affinities for albumins (binding constants in the range 1-15 x 10(4) M(-1)), flavones and flavonols being most tightly bound. Glycosidation and sulfation could lower the affinity to albumin by one order of magnitude depending on the conjugation site. Despite multiple binding of both quercetin and site probes, it can be proposed that the binding of flavonols primarily takes place in subdomain IIA. Significant differences in affinity and binding location are observed for the highly homologous HSA and BSA.
食用富含植物产品的膳食后，膳食黄酮醇可在血浆中以与血清白蛋白结合的共轭物形式被检测到。黄酮醇与白蛋白的结合有望调节黄酮醇的生物利用度。在这项工作中，通过荧光光谱法，采用三种方法研究了结构不同的黄酮类化合物与人和牛血清白蛋白的结合：白蛋白荧光猝灭、黄酮类化合物荧光增强、第二种黄酮类化合物对槲皮素 - 白蛋白复合物荧光的猝灭。后一种方法扩展到已知其高亲和力结合位点位于两个主要亚结构域之一的探针（华法林和丹磺酰 - L - 天冬酰胺用于亚结构域IIA，布洛芬和地西泮用于亚结构域IIIA）。总体而言，黄酮类化合物对白蛋白显示出中等亲和力（结合常数在1 - 15×10⁴ M⁻¹范围内），黄酮和黄酮醇结合最紧密。糖基化和硫酸化可能会使与白蛋白的亲和力降低一个数量级，具体取决于共轭位点。尽管槲皮素和位点探针都存在多重结合，但可以认为黄酮醇的结合主要发生在亚结构域IIA。对于高度同源的人血清白蛋白（HSA）和牛血清白蛋白（BSA），观察到亲和力和结合位置存在显著差异。
