Elucidating the binding mechanism between macluraxanthone and bovine serum albumin: multi-spectroscopic, computational, and biological insights

Abstract

The binding nature of bioactive compounds with serum proteins, especially albumin, is noteworthy studied to achieve successful clinical drug development. Macluraxanthone (MCX), a bioactive xanthone, exhibits diverse pharmacological properties, but its binding interaction with albumin remains poorly understood. In this study, the binding mechanism of MCX and bovine serum albumin (BSA) was investigated using multiple experimental and computational methods. The UV absorption and steady-state fluorescence studies showed that MCX interacts with BSA through a ground-state association. The decrease in the Stern-Volmer constant ( K <inf> sv </inf>) values with increasing temperatures, and the bimolecular quenching rate constant ( k <inf> q </inf>) values in the order of 10¹² M⁻¹ s⁻¹ indicated a static fluorescence quenching mechanism. The association constant ( K <inf> a </inf>) values in the order of 10⁶ M⁻¹ indicated a strong interaction. Thermodynamic parameters suggested that the binding is spontaneously enthalpically controlled. Circular dichroism (CD) and Fourier transform infrared spectroscopy (FTIR) analyses revealed minimal perturbation in the secondary structure of albumin upon interaction with MCX at 0.5 and 2.0 μM, accompanied by a slight reduction in α-helix content. Molecular docking results showed that MCX could interact with multiple binding sites on the BSA. Experimental antioxidants (DPPH and ABTS) were also conducted to explore the effects of the BSA binding towards the biological activities of the compound. Collectively, this study demonstrates the preferable pharmacokinetic profile of MCX, providing beneficial insights and offering a foundation for future therapeutic applications of natural xanthone.