Dihydro-alpha-lipoic acid binds to human serum albumin at Sudlow I binding site

Binding of dihydro-alpha-lipoic acid (DHLA) to human serum albumin (HSA) was characterised in detail in this study. Binding process was monitored by spectroscopic methods and molecular docking approach. HSA binds DHLA with moderate affinity, 0.80 {+/-} 0.007 x 104 M-1. Spectroscopic data demonstrated that the preferential binding site for DHLA on HSA is IIA (Sudlow I). Hydrogen bonds and electrostatic interactions were identified as the key binding interactions. DHLA binding thermally stabilized HSA, yet it had no effect on HSA structure and its susceptibility to trypsin digestion. Molecular docking confirmed that Sudlow I site accommodated DHLA in a certain conformation in order for binding to occur. Molecular dynamic simulation showed that formed complex is stable. Reported results offer future perspectives for investigations regarding the use of DHLA as a dietary intervention but also raise concerns about the effectiveness of alpha-lipoic acid and DHLA in treatment of patients with COVID-19.