Phenytoin-Bovine Serum Albumin interactions - modeling plasma protein – drug binding: A multi-spectroscopy and in silico-based correlation

• Published in: Spectrochimica acta. Part A, Molecular and biomolecular spectroscopy Molecular and biomolecular spectroscopy, 2018-03, Vol.193, p.523-527
• Main Authors: Suresh, P.K., Divya, Naik, Nidhi, Shah, Rajasekaran, R.
• Format: Article
• Language: English
• Subjects: Bovine Serum Albumin (BSA); FTIR; LIGPLOT; Molecular docking; Phenytoin (PHT); UV–visible spectrophotometry
• ISSN: 1386-1425
• DOI: 10.1016/j.saa.2017.12.069

The study focused on the analysis of the nature and site of binding of Phenytoin (PHT) -(a model hydrophobic drug) with Bovine Serum Albumin (BSA) (a model protein used as a surrogate for HSA). Interactions with defined amounts of Phenytoin and BSA demonstrated a blue shift (hypsochromic -change in the microenvironment of the tryptophan residue with decrease in the polar environment and more of hydrophobicity) with respect to the albumin protein and a red shift (bathochromic -hydrophobicity and polarity related changes) in the case of the model hydrophobic drug. This shift, albeit lower in magnitude, has been substantiated by a fairly convincing, Phenytoin-mediated quenching of the endogenous fluorophore in BSA. Spectral shifts studied at varying pH, temperatures and incubation periods (at varying concentrations of PHT with a defined/constant BSA concentration) showed no significant differences (data not shown). FTIR analysis provided evidence of the interaction of PHT with BSA with a stretching vibration of 1737.86cm−1, apart from the vibrations characteristically associated with the amine and carboxyl groups respectively. Our in vitro findings were extended to molecular docking of BSA with PHT (with the different ionized forms of the drug) and the subsequent LIGPLOT-based analysis. In general, a preponderance of hydrophobic interactions was observed. These hydrophobic interactions corroborate the tryptophan-based spectral shifts and the fluorescence quenching data. These results substantiates our hitherto unreported in vitro/in silico experimental flow and provides a basis for screening other hydrophobic drugs in its class. The graphical abstract serves to highlight the hitherto unreported bathochromic and hypsochromic shifts with respect to BSA and phenytoin respectively. For the first time, the interaction was substantiated by the fluorescence data. Also, we report, for the first time, FT-IR data with regards to the type of bonds formed between Phenytoin and BSA (comparative FT-IR-based analysis). Last but not least, we report, for the first time, LIGPLOT data demonstrating a preponderance and commonality in terms of certain hydrophobic interactions and covalent bonds (two most important interactions relevant to certain Pharmacodynamic variables). [Display omitted] To the best of our knowledge, this paper is the first of its kind to demonstrate a hitherto unreported•in vitro/in silico experimental flow that demonstrates interactions between Phenytoin a