Spectroscopic Studies on the Interaction Between Aucubin and Bovine Serum Albumin Without or With Copper II or Iron III

The binding of aucubin to bovine serum albumin in the absence or presence of copper II or iron III has been studied by fluorescence, UV-Vis absorbance, synchronous fluorescence, and circular dichroism spectroscopies at pH 7.40. The results of fluorescence showed that the static quenching mechanism played a major role without or with copper II or iron III, and the quenching constant, binding constant, and binding site number decreased with copper II or iron III at three different temperatures (310 K, 300 K, and 290 K). This indicated that the drug would take effect more promptly in the presence of metal ions than in the absence of them. Thermodynamic parameters revealed that hydrophobic forces played vital roles and the binding process was spontaneous without or with copper II or iron III. The results of synchronous fluorescence showed that the polarity of the microenvironment around tryptophan and tyrosine residues changed insignificantly without or with copper II or iron III. The results of circular dichroism showed that there were slight reductions in the α-helix content of bovine serum albumin. In conclusion, copper II or iron III could reduce the binding ability between aucubin and bovine serum albumin, resulting in enhanced maximum effects of aucubin. The relative knowledge would contribute to the pharmaceutical development and clinical application of aucubin.

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