Unravelling the Interaction Mechanism Between Oryzanol and Human Serum Albumin: An Integrated Approach Using Multispectral Analysis and Molecular Simulations

Gamma-oryzanol (Ory), a major bioactive constituent of rice bran oil, has attracted increasing attention because of its antioxidant and cholesterol-lowering properties. In this study, the interactions between Ory and human serum albumin (HSA) and the underlying molecular mechanisms were investigated. The quenching of HSA fluorescence by Ory occurred via a mixed mechanism, indicating the formation of a stable complex. Thermodynamic analyses and molecular dynamics showed that the HSA-Ory complex was stabilised primarily by hydrogen bonding and van der Waals interactions. Moreover, competitive site marker experiments, complemented by molecular docking and MM-PBSA calculations revealed that Ory specifically targets site I of HSA, engaging in stable interactions with critical residues such as Trp214 and Lys199. Additionally, the dissociation behaviour of Ory was explored using steered molecular dynamics simulations, highlighting the role of specific amino acid residues in regulating the dissociation of Ory from HSA site I. Overall, this study provided molecular insights into the binding mechanisms and interactions between HSA and Ory.