Characterization of binding interaction between magnesium isoglycyrrhizinate and human serum albumin

Magnesium isoglycyrrhizinate (MgIG) is the magnesium salt of 18β-glycyrrhizic acid extracted from licorice, a Chinese traditional medicine. The pharmacokinetic characteristics of MgIG have been widely studied; nevertheless, its target protein and mechanism of action remain unclear. Therefore, the objective of present work was to determine the characteristics of binding between human serum albumin (HSA) and MgIG. The formation of HSA-MgIG complex was studied using spectrometric techniques, LC-MS/MS, and molecular docking calculations. The results of fluorescence study demonstrated the quenching mechanism is definitely static. The negative thermodynamic parameters suggested that the interaction is enthalpically driven and occurs spontaneously. Binding density and probe displacement analysis suggested that MgIG bound to HSA at a single site, determined to be site I. The mean albumin binding rate of MgIG with HSA concentration ranged from 35 to 50 g·L^-1 reached 85.6%. Molecular docking analysis revealed the major residues and interaction forces involved in formation of HSA-MgIG complex, corresponding with the experimental results.