Effects of Inorganic Ions on the Binding of Triflupromazine and Chlorpromazine to Bovine Serum Albumin Studied by Spectrometric Methods

Characterizing the interactions of the antipsychotic drug trifluoperazine with bovine serum albumin: Probing the drug-protein and drug-drug interactions using multi-spectroscopic approaches

Trifluoperazine is a potent antipsychotic drug used in the treatment of neurological disorders. The usage of trifluoperazine is often found to be associated with more adverse side effects as compared to other low-potency antipsychotic agents. Plasma proteins play an inevitable role in determining the pharmacokinetic properties of a drug. Hence, this study was conducted with an aim to characterize the interactions of trifluoperazine with bovine serum albumin and determine the influence of other small molecules on its interaction with serum albumin. Trifluoperazine bound to BSA at two independent sites with K_d values of 9.5 and 172.6 μM. Förster resonance energy transfer and computational docking analysis revealed that both the binding sites of trifluoperazine were located closer to TRP 213 in subdomain IIA of BSA. Evaluation of trifluoperazine-BSA interactions at three different temperatures indicated that there was a stable complex formation between the two molecules at the ground state and that the static quenching mechanism was predominant behind these interactions. Binding studies in the presence of pharmaceutically relevant drugs indicated that warfarin, paracetamol, and caffeine negatively influenced the binding of trifluoperazine on BSA. Lastly, Fourier transformed infrared spectroscopy and circular dichroism spectroscopy indicated that the binding of trifluoperazine induced a conformational change by reducing the α-helical content of BSA. The study implicates that the small molecules which prefer binding to the Sudlow site I of BSA might compete with trifluoperazine for its binding site thereby increasing the concentration of free trifluoperazine in the plasma which could lead to adverse side effects in patients.

Effect of long-chain Fatty acids on the binding of triflupromazine to human serum albumin: a spectrophotometric study

Human serum albumin (HSA) in the blood binds long-chain fatty acids (LCFAs), and the number of bound LCFAs varies from 1 to 7 depending on the physical condition of the body. In this study, the influence of LCFA-HSA binding on drug-HSA binding was studied using triflupromazine (TFZ), a psychotropic phenothiazine drug, in a buffer (0.1 M NaCl, pH 7.40, 37°C) by a second-derivative spectrophotometric method which can suppress the residual background signal effects of HSA observed in the absorption spectra. The examined LCFAs were caprylic acid (CPA), lauric acid (LRA), oleic acid (OLA), and linoleic acid (LNA), respectively. Using the derivative intensity change of TFZ induced by the addition of HSA containing LCFA, the binding mode of TFZ was predicted to be a partition-like nonspecific binding. The binding constant (K M⁻¹) showed an increase according to the LCFA content in HSA for LRA, OLA, and LNA up to an LCFA/HSA molar ratio of 3–4. However, at higher ratios the K value decreased, i.e. for OLA and LNA, at an LCFA/HSA ratio of 6–7, the K value decreased to 40% of the value for HSA alone. In contrast, CPA, having the shortest chain length (8 carbons) among the studied LCFAs, induced a 20% decrease in the K value regardless of its content in HSA. Since the pharmacological activity of a drug is closely related to the unbound drug concentration in the blood, the results of the present study are pharmaco-kinetically, pharmacologically, and clinically very important.

Binding of benzodiazepine drugs to bovine serum albumin: a second derivative spectrophotometric study

The binding constants (K values) of three benzodiazepine drugs to bovine serum albumin were determined by a second derivative spectrophotometric method. Despite the sample and reference samples were prepared in the same way to maintain the same albumin content in each sample and reference pair, the absorption spectra show that the baseline compensation was incomplete because of the strong background signals caused by bovine serum albumin. Accordingly, further quantitative spectral information could not be obtained from these absorption spectra. On the other hand, the calculated second derivative spectra clearly show isosbestic points indicating the complete removal of the residual background signal effects. Using the derivative intensity differences (ΔD values) of the studied benzodiazepine drugs before and after the addition of albumin, the binding constants were calculated and obtained with R.S.D. of less than 8%. The interactions of drugs with bovine serum albumin were investigated using Scatchard's plot. In addition, the consistency between the fractions of bound benzodiazepine calculated from the obtained K values and the experimental values were established. The results indicate that the second derivative method can be advantageously applicable to the determination of binding constants of drugs to serum albumin without prior separation. Moreover, the validity of the proposed method was confirmed.

Analysis of interaction property of bioactive components in Flos Lonicerae Japonicae with protein by microdialysis coupled with HPLC-DAD-MS

Interaction of the Flos Lonicerae Japonicae (FLJ) with protein was studied by microdialysis coupled with HPLC-DAD-MS. Eight compounds were identified by comparing their t(R), UV data and MS data with reference compounds. Microdialysis recoveries and binding degrees of compounds in FLJ with bovine serum albumin (BSA) were determined. Recoveries of microdialysis sampling ranged from 51.3 to 73.2% with relative standard deviation (RSD) below 3.1%, and the binding degrees of those compounds to BSA ranged from 4.8 to 61.2 (0.3 mM BSA) and from 11.1 to 76.2% (0.6 mM BSA), respectively. The results showed that the binding properties of compounds in FLJ were influenced by pH. Furthermore, the binding degrees of five reference compounds were determined separately under the same conditions, the binding degrees of chlorogenic acid, luteolin-3-O-glucoside and 4,5-di-O-caffeoyl quinic acid was lower in FLJ than in single compound solution, on the contrary the binding degree of caffeic acid and rutin was higher in FLJ, which indicated that a significant effects of the interaction of compounds with each other on their binding degrees to BSA. The results showed that there were ten compounds had interaction with BSA, eight of them were the proven active compounds, and the other two compounds had similar binding degree with the proven active compounds, so the ten compounds might possess potential activities.