Studies on the binding of curcumin and glycyrrhetinic acid to human serum albumin by multi-spectroscopic methods and molecular docking approaches

Human serum albumin (HSA) is the most prevalent and important carrier in plasma, and its interaction with drugs may have a significant effect on the efficacy of drugs. Curcumin (CU) and glycyrrhizic acid (GA) are excellent potential anti-cancer candidates, and studies have shown that the combined application of them can significantly enhance the anti-cancer effect. In order to investigate the interaction of binary systems (HSA-CU/GA) and ternary systems (HSA-CU-GA), we employed spectroscopic methods to study the interaction mechanism and binding affinity, and carried out molecular docking with docking tools. The fluorescence quenching spectrum showed that CU and GA all had fluorescence quenching effects on HSA, and the quenching mechanism were static quenching. The binding sites of CU and GA to HSA were both in site I, and the main force were van der Waals forces and hydrogen bonds. The presence of GA enhanced the affinity between CU and HSA, increased the bioavailability of CU and its stability in plasma. The circular dichroism (CD) and three-dimensional fluorescence experiments showed that CU and GA dramatically altered the conformation of HSA, and GA could enhance the influence of CU on the conformation of HSA. This study aimed at exploring the binding properties of CU/GA to HSA, and providing important theoretical support for their combined use.