Non-enzymatic glycation of human serum albumin modulates its binding efficacy towards bioactive flavonoid chrysin: A detailed study using multi-spectroscopic and computational methods

Abstract

The non-enzymatic glycation of plasma proteins by reducing sugars have important consequences on the conformational and functional properties of protein. The formation of advanced glycation end products (AGEs) is responsible for cell death and other pathological conditions. We have synthesized the glycated human serum albumin (gHSA) and characterized the same by using differential spectroscopic measurements. The aim of the present study is to determine the effect of glycation on the binding of human serum albumin (HSA) with bioactive flavonoid chrysin, which possesses anti-cancer, anti-inflammatory and anti-oxidant activities. The interaction of chrysin with HSA and gHSA was studied using multi-spectroscopic, molecular docking and molecular dynamics (MD) simulation techniques. Chrysin quenched the intrinsic fluorescence of both HSA and gHSA by static quenching mechanism. The value of the binding constant (K_b) for the interaction of HSA-chrysin complex (4.779 ± 0.623 × 10⁵ M⁻¹ at 300 K) was found to be higher than that of gHSA-chrysin complex (2.206 ± 0.234 × 10⁵ M⁻¹ at 300 K). Hence, non-enzymatic glycation of HSA significantly reduced its binding affinity towards chrysin. The % α-helicity of HSA was found to get enhanced upon binding with chrysin, and minimal changes were observed for the gHSA-chrysin complex. Site marker probe studies indicated that chrysin binds to subdomain IIA and IIIA of both HSA and gHSA. The results from molecular docking and MD simulation studies correlated well with the experimental findings. Electrostatic interactions followed by hydrogen bonding and hydrophobic interactions played major roles in the binding process. These observations may have some useful insights into the field of pharmaceutics.

Keywords:

• Human serum albumin
• glycation
• binding constant
• molecular docking
• Molecular Dynamics simulation

Acknowledgments

ASR is grateful to the CSIR, Gov’t of India for funding [File No.01(2903)/17/EMR-II]. ASR acknowledges Dr. S. Mitra and Mr. M. A. Rohman for the fluorescence lifetime measurements at Centre for Advanced Studies, Department of Chemistry, North Eastern Hill University, Shillong. The authors are thankful to Dr. Atanu Bhattacharjee, Department of Biotechnology, North Eastern Hill University, Shillong for helping in the lyophilization of the glycated samples. SS thanks TEQIP-III, NIT Meghalaya for fellowship. ASR thanks Department of Bioscience and Bioengineering, IIT Guwahati for CD studies.

Disclosure statement

No potential conflict of interest was reported by the authors.

Additional information

Funding

Supported by Council of Scientific and Industrial Research, [CSIR file no.: 01(2903)/17/EMR-II], Gov't of India.