Spectroscopic studies on the mode of interaction of an anticancer drug with bovine serum albumin

The mechanism of interaction of vinblastin sulphate (VBS) with bovine serum albumin (BSA) has been reported. Association constant for VBS-BSA binding was found to be 3.146+/-0.06 x 10(4) M(-1). Stern-Volmer analysis of fluorescence quenching data showed that the fraction of fluorophore (protein) accessible to the quencher (drug) was close to unity indicating thereby that both tryptophan residues of BSA are involved in drug-protein interaction. The rate constant for quenching, greater than 10(10) M(-1) S(-1), indicated that the drug-binding site is in close proximity to tryptophan residues of BSA. Binding studies in the presence of an hydrophobic probe, 8-anilino-1-naphthalein-sulphonic acid, sodium salt (ANS) indicated that there is hydrophobic interaction between VBS and probe and they do not share common sites in BSA. Thermodynamic parameters obtained from data at different temperatures showed that the binding of VBS to BSA involves predominant hydrophobic forces. The effects of some additives and paracetamol on binding of VBS-BSA have also been investigated. The CD spectrum of BSA in presence of VBS shows that the binding of VBS leads to change in the helicity of BSA.     

Spectrophotometric Determination of Certain Vicinal Dihydroxybenzene Derivatives with Sodium Bismuthate

A simple and accurate spectrophotometric method is developed for the determination of certain vicinal dihydroxybenzene derivatives, namely, dopamine (DPH), levodopa (LD), methyldopa (MD) and pyrocatechol (PC) using sodium bismuthate in an acid medium. The method is based on the formation of a yellow colored product by the oxidation of vicinal dihydroxybenzene derivatives using sodium bismuthate. Beer's law was obeyed over the concentration range of 8–130 g/mL with the maximum absorption at 422–429 nm. The molar absorptivity and Sandell's sensitivity as evaluated from Beer's law data were found to be in the range of 1.02–1.34 × 10^–3L mol^–1cm^–2and 108–185 ng/cm²respectively. The proposed method has been successfully applied for the determination of DPH, LD and MD in injections and tablets of pharmaceutical preparations. The reliability of the methods was established by replicate determinations with the reported and official method.     

Fabrication of the electrochemically reduced graphene oxide-bismuth nanoparticles composite and its analytical application for an anticancer drug gemcitabine

The present study explores an electroreduced graphene oxide-bismuth nanoparticles composite(ErGOBi) as an electrochemical sensor for the determination of an anticancer drug, gemcitabine hydrochloride(GMB). The Er-GOBi interface was prepared by drop casting of bismuth nitrate-graphene oxide suspension on a glassy carbon electrode(GCE) followed by electro-reduction in the potential range of 0.6 V to 1.7 V. SEM, FTIR, EDAX and AFM techniques were employed for the characterization of prepared materials. Cyclic voltammetric and electrochemical impedance spectroscopic methods were used to understand the charge transfer properties of stepwise modification of Er-GOBi/GCE. GMB exhibited an irreversible oxidation peak at 1.144 V on Er-GOBi/GCE in phosphate buffer of p H 3. A 100-fold enhanced oxidation peak current was observed at Er-GOBi/GCE when compared to that at bare GCE.Sensing performance of Er GO-Bi/GCE was optimized by varying peak current dependent parameters.Linear relationship between the peak current and concentration of GMB was observed in the range of 0.1–51.1 mmol/L in differential pulse voltammetric method and 2.1–61.1 mmol/L in linear sweep voltammetric method. The practical utility of the proposed sensor, Er-GOBi/GCE was demonstrated by determining GMB in pharmaceutical formulations and spiked urine samples.     

Spectrophotometric determination of vanadium(V) in minerals, steels, soil and biological samples using phenothiazine derivatives.

Two simple, rapid and sensitive spectrophotometric methods have been proposed for the determination of vanadium(V) using butaperazine dimaleate (BPD) and propionyl promazine phosphate (PPP). These methods are based on the formation of red-colored radical cations on reaction with vanadium(V) in phosphoric acid medium, with their absorbance maxima at 513 nm. Beer's law is valid over the concentration range of 0.25-5.0 micrograms ml-1 and 0.2-4.0 micrograms ml-1, with Sandell's sensitivity values of 6.1 ng cm-2 and 6.0 ng cm-2 for BPD and PPP respectively. The proposed methods have been successfully applied to the analysis of vanadium steels, minerals, biological samples and soil samples.     

Sensitive extractive spectrophotometric methods for the determination of trazodone hydrochloride in pharmaceutical formulations

Two simple, rapid and sensitive extractive spectrophotometric methods have been developed for the assay of trazodone hydrochloride (TRH) in pure and pharmaceutical formulations. These methods are based on the formation of chloroform soluble ion-association complexes of TRH with bromothymol blue (BTB) and with bromocresol purple (BCP) in KCl-HCl buffer of pH 2.0 (for BTB) and in NaOAc-AcOH buffer of pH of 3.6 (for BCP) with absorption maximum at 423 nm and at 408 nm for BTB and BCP, respectively. Reaction conditions were optimized to obtain the maximum color intensity. The absorbance was found to increase linearly with increase in concentration of TRH, which was corroborated by the calculated correlation coefficient values (0.9996, 0.9945). The systems obeyed Beer's law in the range of 0.2-14.5 and 0.2-14.1 microg/ml for BTB and BCP, respectively. Various analytical parameters have been evaluated and the results have been validated by statistical data. No interference was observed from common excipients present in pharmaceutical formulations. The proposed methods are simple, accurate and suitable for quality control applications.     

Spectroscopic studies and life time measurements of binding of a bioactive compound to bovine serum albumin and the effects of common ions and other drugs on binding

The mechanism of binding of anti-inflammatory drug, nimesulide (NIM) with bovine serum albumin (BSA) was investigated by fluorescence, absorption, circular dichroism (CD) and lifetime measurements under simulative physiological conditions. The analysis of fluorescence data indicated the presence of both dynamic and static quenching mechanism in the binding. Various binding parameters have been evaluated. The CD spectral data revealed the decrease in alpha-helical content of BSA from 70.9% (in free BSA) to 42.03% (in bound form) thereby indicating the conformational change in BSA upon binding. The binding of NIM to BSA was also confirmed by absorption spectra. Based on the F?rster's theory of non-radiation energy transfer, the binding average distance, r between the donor (BSA) and acceptor (NIM) was found to be 2.17 nm. The association constants of NIM-BSA decreased in presence of the common ions and other drugs thereby indicating the availability of higher concentration of free drug (NIM) in plasma.     

Indirect Spectrofluorimetric Determination of Piroxicam and Propranolol Hydrochloride in Bulk and Pharmaceutical Preparations

A simple and sensitive indirect spectrofluorimetric method for the assay of piroxicam (PX) and propranolol hydrochloride (PPH) in the pure form and in pharmaceutical formulations is proposed. This method is based on the oxidation of PX and PPH by a known excess of N-bromosuccinimide (NBS) followed by the reaction of the excess NBS with methdilazine hydrochloride (MDH) to yield fluorescent species. The fluorescence intensities were measured at 377 nm after excitation at 343 nm. The fluorescence intensities decrease linearly with an increase in concentration of PX and PPH over the ranges of 0.2–8.0 and 0.4–18.0 g/mL respectively. The common excipients and additives did not interfere in the determination. The proposed method has been successfully applied for the determination of PX and PPH in pharmaceutical formulations. The results have been validated by statistical data.     

Binding of an Anti-inflammatory Drug Lornoxicam with Blood Proteins: Insights from Spectroscopic Investigations

The interaction between an anti-inflammatory drug, lornoxicam (LXM) and protein (human serum albumin and bovine serum albumin) was studied by spectroscopic techniques (Fluorescence, synchronous, FT-IR, UV-vis absorption and circular dichroism). The quenching mechanism of fluorescence of the protein by the drug was discussed. Based on the interaction studies carried out at different temperatures by spectrofluorometry, the binding constant and the number of binding sites for drug on protein have been evaluated. The nature of binding force operating between the drug and protein was proposed to be electrostatic and hydrophobic based on thermodynamic parameters. The distance r between the donor (protein) and acceptor (drug) was determined based on the Förster’s theory of non-radiation energy transfer and found to be 2.38 nm and 2.56 nm for LXM-BSA and LXM-HSA respectively. Displacement studies with different site probes revealed that the drug bound to the hydrophobic pocket located in sub domain IIA; that is to say, Trp-214 was near or within the binding site. Circular dichroism data of protein in the presence of drug revealed the decreased α-helicity and hence changes in secondary structure of protein. The effects of some common ions were also investigated.     

Spectrophotometric determination of cerium(IV) using a phenothiazine derivative.

A simple, rapid and sensitive spectrophotometric method has been proposed for the determination of cerium(IV) using a phenothiazine derivative, propionyl promazine phosphate (PPP). This method is based on the formation of a red-colored radical cation upon a reaction of PPP with cerium(IV) in a phosphoric acid medium having maximum absorbance at 513 nm. Beer's law is valid over the concentration range of 1-11 microg/ml with a Sandell's sensitivity value of 16.14 ng/cm2. The proposed method has been successfully applied to the analysis of magnesium-base cerium alloys and synthetic mixtures corresponding to various cerium alloys. Other phenothiazine derivatives viz. butaperazine dimaleate and propericiazine were also used for the determination of cerium(IV).