BINDING OF ANTHRAQUINONES AND FLAVONOIDS TO BOVINE SERUM-ALBUMIN

Binding of 14 kinds hydrophobic compounds of anthraquinones and flavon oids, which distribute extensively in many Chinese herbal medicine, to bovine serum albumin (BSA) were studied using centrifugal ultrifiltra tion. The binding data was analyzed according to Scatchard model, and the binding constants and the binding site number were obtained, respe ctively. The results show that the affinity of these compounds to BSA increases as their hydrophobicity higher except gertiopicrin. Competit ive binding studies indicate that L-tryptephan and emodin share one pr imary site, addition of excess L-Trp will result in the displacement o f one molar equivalence emodin. In the presence of low concentration o leate, the six homogeneous sites of emodin are distinguished into two classes: n1 = 2, n2 = 4, the total number of binding sites remains unc hangeable while the binding constants decrease. When the oleate concen tration is high enough, emodin will thoroughly not bind to BSA. The te mperature dependence of the binding constants reveals that the binding enthalpy is nearly zero. On this basis, the mechanism of the binding reaction was discussed in brief.