A spectral deciphering the perturbation of model transporter protein (HSA) by antibacterial pyrimidine derivative: Pharmacokinetic and biophysical insights

Steady state fluorescence and UV–vis absorption spectroscopic techniques have been exploited to explore the binding interaction of a antibacterial pyrimidine derivative 2-amino-6-hydroxy-4-(4-hydroxyphenyl)-pyrimidine-5-carbonitrile (AHHPPC) with the model transporter protein, human serum albumin (HSA) under the physiological conditions. It exhibits antibacterial activity against Escherichia coli and Staphylococcus aureus. Analysis of fluorescence quenching data of HSA at different temperatures using Stern–Volmer methods revealed the formation of AHHPPC–HSA complex with binding affinities of the order 104 M−1. The binding site number (n ≈ 1) and corresponding thermodynamic parameters (ΔG), (ΔH) and (ΔS) were calculated, indicated that binding reaction was endothermic and the hydrophobic interactions plays a major role in stabilizing the complex. The binding distance (r = 3.13 nm) between donor (HSA) and acceptor (AHHPPC) was obtained according to FRET. Changes in the albumin secondary structure imparted by the compound was confirmed using synchronous fluorescence, electronic absorption, circular dichroism (CD) and three-dimensional (3D) fluorescence spectroscopy. All these experimental results clarified that AHHPPC could bind to HSA and be effectively transported and eliminated in body, which could be a useful guideline for further drug design.