Analysis of aceclofenac and bovine serum albumin interaction using fluorescence quenching method for predictive, preventive, and personalized medicine

Background

The study of the interaction of a drug with plasma protein is very important because drug-protein binding plays an important role in determination of pharmacological and toxicological properties of drugs. Our study was designed to investigate the interaction between aceclofenac and bovine serum albumin (BSA) using fluorescence spectroscopy at different temperatures (298 and 308 K).

Methods

Fluorescence spectroscopy was used to carry out the study. Fluorescence quenching constant was determined from Stern-Volmer equation. Van’t Hoff equation was used to determine the thermodynamic parameters such as free energy (ΔG), enthalpy (ΔH), and entropy (ΔS).

Results

The experimental data showed that the quenching of BSA by aceclofenac was due to a formation of a BSA-aceclofenac complex with probable involvement of both tryptophan and tyrosine residues of BSA. Dynamic quenching was shown for BSA by aceclofenac at the experimental conditions. The values of thermodynamic parameters indicated that the hydrophobic forces played major roles for BSA-aceclofenac complexation. The binding number (n) was found to be ≈1 indicating that 1 mol of BSA bound with 1 mol of aceclofenac. The binding affinity of aceclofenac to BSA was calculated at different temperatures. It was shown that the binding constant decreased with increasing temperatures indicating that stability of the BSA-aceclofenac complex decreased with increasing temperatures.

Conclusions

The interaction of aceclofenac with BSA was successfully explored using a fluorescence spectroscopic technique.

Isolation, Characterization of a Potential Degradation Product of Aspirin and an HPLC Method for Quantitative Estimation of Its Impurities

In this work, a new degradation product of Aspirin was isolated, characterized and analyzed along with other impurities. New unknown degradation product referred as UP was observed exceeding the limit of ICH Q3B identification thresholds in the stability study of Aspirin and Dipyridamole capsule. The UP isolated from the thermal degradation sample was further studied by IR, Mass and (1)H NMR spectrometry, revealing structural similarities with the parent molecule. Finally, UP was identified as a new compound generated from the interaction of Aspirin and Salicylic acid to form a dehydrated product. A specific HPLC method was developed and validated for the analysis of UP and other Aspirin impurities (A, B, C, E and other unknown degradation products). The proposed method was successfully employed for estimation of Aspirin impurities in a pharmaceutical preparation of Aspirin (Immediate Release) and Dipyridamole (Extended Release) Capsules.

Physiological concentrations of albumin favor drug binding

We exploit the direct measurements of spin labeled drugs to study drug binding to/release from protein using EPR spectroscopy.

Study of single and double chain surfactant–cobalt(iii) complexes and their hydrophobicity, micelle formation, interaction with serum albumins and antibacterial activities

Single and double chain surfactant–cobalt(iii) complexes show respectively, electrostatic and hydrophobic interactions with serum albumins.

Enantioselective binding interaction of the metolachlor pesticide enatiomers with bovine serum albumin--a spectroscopic analysis study

Enantioselective binding interaction of the pesticides, metolachlor (RAC-metolachlor) and its S-enantiomer (S-metolachlor), with bovine serum albumin (BSA) was investigated by fluorescence and UV-vis absorption spectroscopy. Both RAC- and S-metolachlors quenched the intrinsic fluorescence of BSA via a static mechanism, and various binding parameters indicated that electrostatic forces were involved in the binding of both of these compounds. Site marker competitive experiments demonstrated that S-metolachlor bound to site I of BSA, while R-metolachlor bound to site II, indicating the importance of enantiomeric factors for binding site selection. Further experiments showed that S-metolachlor had a higher binding affinity to BSA than R-metolachlor. The obtained spectral data were resolved with use of the multivariate curve resolution-alternating least squares method (MCR-ALS), and the extracted concentration profiles of the reacting species in the interaction were obtained. These profiles indicated that S-metolachlor was the main active constituent of RAC-metolachlor for binding with BSA, and these findings have significant implications in providing an explanation why S-metolachlor is the preferred herbicide in practice than RAC-metolachlor.