Synthesis of pyrazole-3-carboxylic acid was progressed via two different protocols, one of which is solid state. Pyrazole-3-carboxylic acid was converted into different derivatives such as ester, urea, amide and nitrile. The amide compound was converted to nitrile using SOCl2 and DMF. Solid state heating of carboxylic acid gave decarboxylated product. Cyclization of tetra-substituted pyrazole with hydrazines resulted in pyrazolopyridazinones. The antimicrobial activities of the synthesized pyrazole derivatives against Bacillus cereus, Escherichia coli, Micrococcus luteus, Staphylococcus aureus, and Saccharomyces cerevisiae were evaluated. One of the pyrazole derivatives which possess nitro group showed antimicrobial activity in only B. cereus, a Gram-positive bacteria, with an MIC of 128 μg/mL.

Introduction: Macitentan is an endothelin receptor antagonist drug used in the treatment of pulmonary arterial hypertension. Materials and Methods: A new, sensitive, simple, accurate and rapid ultra-performance liquid chromatography in combination with tandem triple quadruple mass spectrometry (UPLC-MS/MS) method has been developed and validated for the determination of macitentan in pharmaceutical formulations. Macitentan and bosentan which are used as internal standard (IS) were detected using atmospheric pressure chemical ionization (APCI) in positive ion, multiple reaction monitoring (MRM) mode by monitoring mass transitions (precursor to product) m/z 589.1→203.3 and 552.6→311.5, respectively. Chromatographic separation was carried out on reverse phase C18 column (5 µm, 4.6 * 150 mm). Water containing 0.2 % acetic acid in acetonitrile (10:90, v/v) was used as the mobile phase in the isocratic elution. The system was optimized with injection volume of 10 µL, column temperature of 35 °C and flow rate of 1 mL min-1 Retention times were 1.97 min for macitentan and 1.72 min for IS. Results and Discussion: The calibration curve with a high correlation coefficient (0.9997) was linear range 0.5-500 ng mL-1. The lower limit of quantitation (LLOQ) and average recovery values were determined as 0.5 ng mL-1 and 99.7 %, respectively. The developed novel method has been successfully applied for the determination of macitentan in pure form and pharmaceutical formulations. Conclusion: The present method is the first study developed and validated for the determination of macitentan from the pharmaceutical preparations and pure form by UPLC-MS/MS method in the literature.

Macitentan is an endothelin receptor antagonist commonly used in the treatment of pulmonary arterial hypertension (PAH). A novel, rapid, simple and sensitive UPLC–MS/MS method was developed and validated for pharmacokinetic study and the determination of macitentan in PAH patients. Macitentan and bosentan, which are used as internal standards, were detected using atmospheric pressure chemical ionization in positive ion and multiple reaction monitoring mode by monitoring the mass transitions m/z 589.1 → 203.3 and 552.6 → 311.5, respectively. Chromatographic separation was performed on a reverse‐phase C18 column (5 μm, 4.6 × 150 mm) with an isocratic mobile phase, which consisted of water containing 0.2% acetic acid–acetonitrile (90:10, v/v) at a flow rate of 1 mL/min. Retention times were 1.97 and 1.72 min for macitentan and IS, respectively. The calibration curve with high correlation coefficient (0.9996) was linear in the range 1–500 ng/mL. The lower limit of quantitation and average recovery values were determined as 1 ng/mL and 89.8%, respectively. This method is the first UPLC–MS/MS method developed and validated for the determination of macitentan from human plasma. The developed analytical method was fully validated for linearity, selectivity, specificity, accuracy, precision, sensitivity, stability, matrix effect and recovery according to US Food and Drug Administration guidelines. The developed method was applied successfully for pharmacokinetic study and the determination of macitentan in PAH patients.