Dapoxetine is a selective serotonin reuptake inhibitor, used to treat premature ejaculation in men. Dapoxetine may interact with the DNA and hence this study investigated dapoxetine and calf thymus DNA (ctDNA) binding interaction. The interaction study of ligands to DNA is of importance in the development of molecular probes and therapeutic agents. Spectroscopic techniques including spectrofluorometry and spectrophotometry were employed to study this interaction. Fluorescence studies indicated a static quenching mechanism between dapoxetine and ctDNA. Groove binding was suggested as the mode of interaction between dapoxetine and ctDNA based on UV absorption, circular dichroism (CD) spectroscopy, iodide quenching and molecular docking studies. The studies conducted at three different temperatures 298,303 and 310 K indicated a strong binding interaction at higher temperatures. Thermodynamic studies conducted indicated involvement of hydrophobic interaction between ctDNA and dapoxetine and were entropy-driven. Ethidium bromide probe study suggested that dapoxetine does not bind to ctDNA in an intercalative fashion. Iodide quenching studies further proved the non-intercalative binding of ctDNA with dapoxetine. Ionic strength studies conducted ruled out the electrostatic binding mechanism between ctDNA and dapoxetine. Molecular docking analysis performed for the dapoxetine with calf thymus DNA (ctDNA) interaction and confirmed minor groove binding of dapoxetine to ctDNA. The study helped to reveal the binding interaction mechanism between dapoxetine and ctDNA.

In this study, an HPLC method with ultraviolet (UV) detection was developed and validated for determination of pazopanib (PAZ), a multi-targeted tyrosine kinase (TK) inhibitor in bulk drug, tablets formulation, and in human plasma. Oxamniquine (OXA) was used as internal standard (IS). The analytical column used for the separation was Nucleosil CN with dimensions (i.d. 250 X 4.6 mm and particle size 5 μπι). The separation was carried out in isocratic mode with mobile phase constituting acetonitrile:100 mM sodium acetate buffer (pH 4.5); 40:60, v/v. The developed method was linear in the concentration range of 2-12 μg mL-1 and had a correlation coefficient (r = 0.9998, n = 6). The limits of detection and quantitation (LOD and LOQ) were 0.27 and 0.82 μg mL-1, respectively. The relative standard deviations for the inter- and intra-assay precisions were below 3.61 % and the accuracy of the method was 96.69-104.15 %. The degradation products were resolved from the intact drug, proving the stability-indicating property of the proposed method. The recovery values were 100.17-103.98 % (± 1.81-4.02) for determination of PAZ in human plasma. The results indicated the versatility of the new method in estimation of PAZ during pharmaceutical quality control (QC) and therapeutic drug monitoring (TDM).

This study was designed to develop and validate a UPLC-MS/MS method for quantification of neratinib in human plasmsa. Neratinib is an irreversible tyrosine kinase inhibitor against the pan-ErbB (ErbB-1, -2, -4) receptor. UPLC-MS/MS is an excellent analytical methodology for rapid biomedical analysis, decreasing the time for analysis and maintaining good efficiency. Crizotinib was used as internal standard (IS). Samples where extracted by plasma protein precipitation (PPT) procedure with acetonitrile and methanol and analysis was performed on a C18 Acquity UPLC BEH TM column. The ion transitions where recorded in positive ion multiple reaction monitoring mode m/z 557.51 → 112.17 for neratinib and m/z 450.0 → 260.0 for IS. The mobile phase used was methanol:water: formic acid (70:30:0.1 %, v/v/v) with a flow rate of 0.3 mL min-1. The linearity of the assay was found to be 4-500 ng mL-1 for neratinib in human plasma with lower limit of quatification of 4 ng mL-1. The intra- and inter-assay precision relative standard deviations did not exceed 10.99 and mean extraction recovery was found to be 69.12 ± 3.58.