Study on the stereoselective binding of cytosine nucleoside enantiomers to human serum albumin

Interactions of diclazuril enantiomers with serum albumins: Multi-spectroscopic and molecular docking approaches

In this work, multi-spectroscopic and molecular docking methods have been conducted in the investigation of enantioselective interactions between diclazuril enantiomers and human/bovine serum albumins (HSA/BSA). The binding constants between serum albumins (SAs) and diclazuril enantiomers revealed that SAs exhibited stronger binding affinity for (R)-diclazuril than (S)-enantiomer. In addition, the fluorescence quenching of SAs induced by diclazuril enantiomers was ascribed to static quenching mechanism, in which hydrogen bonds and Van der Waals forces were the main interactions. According to the thermodynamic study, binding of diclazuril enantiomers and SAs was an exothermic process driven by enthalpy change. Then, circular dichroism spectroscopy of SAs with diclazuril enantiomers revealed that the SAs conformation had changed in the presence of diclazuril. Moreover, molecular docking technology was applied in exploration of interactions between SAs and diclazuril enantiomers. The docking energy between SAs and (R)-diclazuril was larger than (S)-diclazuril, which indicated that the affinity of SAs with (R)-diclazuril was stronger than (S)-enantiomer. This work may provide valuable information for explaining differences in pharmacokinetics and residue elimination of diclazuril enantiomers in living organisms.

A simple method for obtaining human albumin and its use for in vitro interaction assays with indole-thiazole and indole-thiazolidinone derivatives

This work aimed to develop a simple and low-cost method to obtain human serum albumin (HSA) and its consequent application for in vitro drug interaction assays. The HSA was purified by classic principles of plasma precipitation and thermocoagulation, using a multiple-stage fractionation. The quality of the final product was assessed by electrophoresis, protein dosage by the Lowry method and the pharmacopeial thermal stability. At the end, an isotonic solution of HSA with a total protein concentration of 2.7 mg·mL^-1 was obtained, which was visualized as a single band corresponding to the molecular weight of 66 kDa. After the thermal stability test, there was no indication of turbidity or color change of the solution. Finally, the HSA was useful for interaction assays with indole-thiazole and indole-thiazolidinone derivatives through UV-vis absorption and fluorescence spectroscopic studies, as well as by docking molecular analysis. Derivatives quenched the intrinsic fluorescence of HSA, disrupted the tryptophan residues microenvironment, and probably bind at Sudlow's site I. Therefore, the simplified methodology developed in this work proved to be effective in obtaining HSA that can be applied to research goals including drug interaction assays.

Enantioresolution and Binding Affinity Studies on Human Serum Albumin: Recent Applications and Trends

The interaction between proteins and drugs or other bioactive compounds has been widely explored over the past years. Several methods for analysis of this phenomenon have been developed and improved. Nowadays, increasing attention is paid to innovative methods, such as high performance affinity liquid chromatography (HPALC) and affinity capillary electrophoresis (ACE), taking into account various advantages. Moreover, the development of separation methods for the analysis and resolution of chiral drugs has been an area of ongoing interest in analytical and medicinal chemistry research. In addition to bioaffinity binding studies, both HPALC and ACE al-low one to perform other type of analyses, namely, displacement studies and enantioseparation of racemic or enantiomeric mixtures. Actually, proteins used as chiral selectors in chromatographic and electrophoretic methods have unique enantioselective properties demonstrating suitability for the enantioseparation of a large variety of chiral drugs or other bioactive compounds. This review is mainly focused in chromatographic and electrophoretic methods using human serum albumin (HSA), the most abundant plasma protein, as chiral selector for binding affinity analysis and enantioresolution of drugs. For both analytical purposes, updated examples are presented to highlight recent applications and current trends.

Comparison of Pinoresinol and its Diglucoside on their ADME Properties and Vasorelaxant Effects on Phenylephrine-Induced Model

Pinoresinol (PINL) and pinoresinol diglucoside (PDG), two natural lignans found in Eucommia ulmoides Oliv. (Duzhong), have several pharmacological activities. However, there is no report available on their absorption, distribution, metabolism, and elimination (ADME) properties. Given the possible wide spectrum of their application in therapeutic areas, this area should be investigated. This work studied the in vitro ADME properties of PDG and PINL, including their kinetic solubility, permeability across monolayer cells (PAMPA), protein binding, and metabolic stabilities in liver microsomes. The in vivo pharmacokinetic study and in vitro vasorelaxant effects on isolated phenylephrine-induced aortic rings of PINL and PDG were also investigated. It was found that both of their kinetic solubility in PBS (pH 7.4) was greater than 100 μM, indicating that they are both soluble compounds. The permeability investigations (P_eff) by PAMPA indicated that PINL had higher permeability than PDG (p < 0.05). Both components represented moderate plasma protein binding activities (average binding rate in human plasma: PINL 89.03%, PDG 45.21%) and low metabolic rate (t_1/2 in human liver microsome: PINL 1509.5 min, PDG 1004.8 min). Furthermore, the results of pharmacokinetic studies indicated that PINL might be eliminated less quickly than PDG from the rat plasma, and its cumulative urinary excretion was much lower than that of PDG. The phenylephrine-induced aortic rings demonstrated concentration-dependent vasorelaxation in PDG, PINL, or their combination group. The vasorelaxant effects of PINL were more obvious than those of PDG, whereas the vasorelaxant effect of the combinations was significantly better than that of the single component (p < 0.05). The similarity or difference between PINL and its diglucoside in these pharmaceutical aspects may offer valuable insights into the further exploration of lignans and might contribute to relevant studies involving natural products with similar molecular structure and their glucosides.

Testing for Ketoprofen Binding to HSA Coated Magnetic Nanoparticles under Normal Conditions and after Oxidative Stress

Binding and transport of ligands is one of the most important functions of human blood serum proteins. Human serum albumin is found in plasma at the highest concentration. Because of this, it is important to study protein–drug interactions for this albumin. Since there is no single model describing this interaction, it is necessary to measure it for each active substance. Drug binding should also be studied in conditions that simulate pathological conditions of the body, i.e., after oxidative stress. Due to this, it is expected that the methods for testing these interactions need to be easy and fast. In this study, albumin immobilized on magnetic nanoparticles was successfully applied in the study of protein–drug binding. Ketoprofen was selected as a model drug and interactions were tested under normal conditions and artificially induced oxidative stress. The quality of obtained results for immobilized protein was confirmed with those for free albumin and literature data. It was shown that the type of magnetic core coverage does not affect the quality of the obtained results. In summary, a new, fast, effective, and universal method for testing protein–drug interactions was proposed, which can be performed in most laboratories.

Extended fluorescent uridine analogues: synthesis, photophysical properties and selective interaction with BSA protein

The improvement in fluorescence properties of 2′-deoxyuridine was made possible by the introduction of (hetero)aromatic moieties at the C–5 position of uridine with alkenyl/phenyl/styryl linkers to create a library of useful fluorescent nucleosides.