Probing the interaction of iminium form of sanguinarine with human salivary α-amylase by multi-spectroscopic techniques and molecular docking

Abstract

Human salivary α-Amylase (HSAmy) non-catalytic but cellular interaction with sanguinarine (SG), a bioalkaloid with a high therapeutic promise, was sought through multiple spectroscopic approaches and molecular docking under simulated salivary physiological conditions. The formation of the stable HSAmy-sanguinarine complex was from a coalesce of static and dynamic fluorescence quenching mechanisms. The enzyme has one binding site for sanguinarine ( iminium form) with a binding constant (Ka) of 1.14 × 104 L·mol−1 at 25° C. The values of enthalpy change (ΔH) and entropy change (ΔS) were found to be 7.46 kJ mol−1 and 102.68 J·mol−1 K−1, respectively at pH 6.4. This indicated that the formation of the HSAmy-sanguinarine complex was an endothermic reaction and entropy-driven process, consequently perturbing the enzyme secondary and tertiary structures. HSAmy intrinsic surface hydrophobicity was also traded-off for the stabilization of the complex formation. The spontaneous interaction was predominantly characterized by hydrophobic (π → π) bonding. Sanguinarine (iminium) prefentially and prudentially binds, with high energy of −9.5 kcal/mol, to the HSAmy active site. The salient role of HSAmy as a reluctant surrogate payload for sanguinarine (iminium) is undeniable, but the interaction has greater pharmcological significance in sugar regulation and HSAmy linked oral health challenges.