Biomolecular interaction of hydralazine with human serum albumin (HSA) was studied by fluorescence, ultravoilet, three-dimensional, synchronous, Fourier transform infrared, lifetime fluorescence, resonance Rayleigh scattering, circular dichroism, and molecular docking techniques. The intrinsic fluorescence of HSA was quenched by a static quenching mechanism. The effect of β-cyclodextrin on binding was studied. Binding constants and number of binding sites were evaluated using the Stern−Volmer equation. Thermodynamic parameters (ΔH°, ΔG°, and ΔS°) indicate the involvement of hydrogen bonding with weak van der Waals forces in the interaction. The average binding distance (r) between the HSA and hydralazine was calculated by Fourier resonance energy transfer theory. Molecular docking study confirms the drug binding sites and interaction of hydralazine with amino acid residues.

Biomolecular interaction of carisoprodol (CAP) with bovine serum albumin (BSA) has been studied by fluorescence and UV-visible spectroscopy and confirmed by multispectroscopic methods including molecular docking studies. The intrinsic intensity of BSA was quenched by dynamic quenching mechanism. The binding constant and number of binding sites were calculated according to Stern-Volmer equation. Effect of β-Cyclodextrin on the binding has been studied. Thermodynamic parameters were calculated which reveal the involvement of hydrophobic interactions in the binding. Based on the Fӧrster's theory of non-radiation energy transfer, the average binding distance(r) between BSA and CAP was evaluated. Spectral results showed that the binding of CAP to BSA induced conformational changes in BSA. Molecular docking study confirms the drug binding sites and interaction of CAP with amino acid residues. 2 protein. Therapeutic effectiveness of drugs depends on their binding ability and the extent of binding of the drug to the organism.Carisoprodol (N-isopropyl-2 methyl-2-propyl-1, 3-propanediol dicarbamate) is a centrally acting muscle relaxant drug for acute painful musculoskeletal treatments (Fig. 1A). 1 Upon being ingested and metabolized, drugs can have ability to form substances called metabolites.Similarly, carisoprodol is metabolized to a pharmacologically active compound meprobamate which is indicated for the treatment of anxiety. 2 The pharmacological effects of carisoprodol is due to the combination of the effects of carisoprodol and meprobamate. In addition to the desired skeletal muscle-relaxing effects, carisoprodol and meprobamate also produce weak anticholinergic, antipyretic, and analgesic effects. 3 Serum albumins are the most abundant plasma proteins found in the circulatory system of wide veriety of organisms. 4 Bovine serum albumin (BSA) consists of three linearly arranged domains (I-III) that are composed of two subdomains (A and B) ( Fig. 1(B)). 5 There are two tryptophan residues (Trp134 and Trp213), of which Trp134 is located on the surface of the molecule and Trp213 resides in the hydrophobic pocket. There is evidence of conformational changes of serum albumin induced by its interaction with low molecular weight dyes and drugs, which appear to affect secondary and tertiary structures of proteins. 6 β-Cyclodextrin (β-CD), is composed of seven units of D(+)-glucopyranose units joined by α-1, 4-glycosidic bonds arranged in a truncated cone-shaped structure. 7 As one of the water-soluble cyclic oligosaccharides, it can form inclusion complexes with a large variety of organic and inorganic compounds, which may improve the solubility, stability and bioavailability of guest molecules. As a result, β-CD has been widely applied in food research, organic synthesis, environment protection and especially in the area of pharmacological science. 8 β-Cyclodextrins are used as additives with drugs (mixed with drug solution) to improve their stability, solubility and cover up the smell of medicine.

Spectrofluoremetric technique was employed to study the binding behavior of hydralazine with bovine serum albumin (BSA) at different temperatures. Binding study of bovine serum albumin with hydralazine has been studied by ultraviolet-visible spectroscopy, fluorescence spectroscopy and confirmed by three-dimensional, synchronous, circular dichroism, and Raman spectroscopic methods. Effect of β-cyclodextrin on binding was studied. The experimental results showed a static quenching mechanism in the interaction of hydralazine with bovine serum albumin. The binding constant and the number of binding sites are calculated according to Stern-Volmer equation. The thermodynamic parameters ∆H(o) , ∆G(o) , ∆S(o) at different temperatures were calculated. These indicated that the hydrogen bonding and weak van der Waals forces played an important role in the interaction. Based on the Förster's theory of non-radiation energy transfer, the binding average distance, r, between the donor (BSA) and acceptor (hydralazine) was evaluated and found to be 3.95 nm. Spectral results showed that the binding of hydralazine to BSA induced conformational changes in BSA. The effect of common ions on the binding of hydralazine to BSA was also examined. Copyright © 2016 John Wiley & Sons, Ltd.

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