Synthesis of Novel Pyridopyridazin-3(2H)-one Derivatives and Evaluation of Their Cytotoxic Activity against MCF-7 Cells

A series of pyridopyridazin-3(2H)-one derivatives was synthesized in two facile steps. Mannich-type three-component condensation afforded the 2,6-diaryl piperidin-4-one derivatives, which underwent intramolecular cyclization in the presence of hydrazine or phenylhydrazine to yield the corresponding pyridopyridazin-3(2H)-one derivatives. All the derivatives of pyridopyridazin-3(2H)-one, except 3e and 3f, showed moderate activity against human breast adenocarcinoma (MCF-7) cells. The higher degree of inhibition of MCF-7 cell proliferation shown by 2a–2f indicates the significance of the amide proton in pyridopyridazin-3(2H)-one derivatives.

1,4-Dihydropyridine Calcium Channel Blockers: Homology Modeling of the Receptor and Assessment of Structure Activity Relationship

1,4-Dihydropyridine (DHP), an important class of calcium antagonist, inhibits the influx of extracellular Ca+2 through L-type voltage-dependent calcium channels. Three-dimensional (3D) structure of calcium channel as a receptor for 1,4-dihydropyridine is a step in understanding its mode of action. Protein structure prediction and modeling tools are becoming integral parts of the standard toolkit in biological and biomedical research. So, homology modeling (HM) of calcium channel alpha-1C subunit as DHP receptor model was achieved. The 3D structure of potassium channel was used as template for HM process. The resulted dihydropyridine receptor model was checked by different means to assure stereochemical quality and structural integrity of the model. This model was achieved in an attempt to understand the mode of action of DHP calcium channel antagonist and in further computer-aided drug design (CADD) analysis. Also the structure-activity relationship (SAR) of DHPs as antihypertensive and antianginal agents was reviewed, summarized, and discussed.

Synthesis and Antibacterial Screening of Some 1-Aroyl-3-aryl Thiourea Derivatives

A series of 1-aroyl-3-aryl thioureas derivatives were synthesized and evaluated for antibacterial activity. The results indicated that the compounds possessed higher activity against gram-negative bacteria than gram-positive bacteria. Amongst all these compounds, C18 (89.4%) exhibited the greatest antibacterial activity against gram-negative bacteria while C5 (85.6%) displayed maximum antibacterial activity against gram-positive bacteria. Preliminary study of the structure-activity relationship revealed that an electronic factor on aryl rings had a great effect on the antibacterial activity of these compounds.

Sulfonamide Based β-Carbonic Anhydrase Inhibitors: 2D QSAR Study

The carbonic anhydrases (CAs) (or carbonate dehydratases) form a family of metalloenzymes that catalyze the rapid interconversion of carbon dioxide and water to bicarbonate and protons (or vice versa), a reversible reaction that occurs rather slowly in the absence of a catalyst. The β-CAs have been characterized in a high number of human pathogens, such as the fungi/yeasts Candida albicans, Candida glabrata, Cryptococcus neoformans, and Saccharomyces cerevisiae and the bacteria Helicobacter pylori, Mycobacterium tuberculosis, Haemophilus influenzae, Brucella suis, and Streptococcus pneumonia. The β-CAs in microorganisms provide physiological concentration of carbon dioxide and bicarbonate (CO2/HCO3-) for their growth. Inhibition of β-CAs from the pathogenic microorganism is recently being explored as a novel pharmacological target to treat infections caused by the these organisms. The present study aimed to establish a relationship between the β-CAs inhibitory activity for structurally related sulphonamide derivatives and the physicochemical descriptors in quantitative terms. The statistically validated two-dimensional quantitative structure activity relationship (2D QSAR) model was obtained through multiple linear regression (MLR) analysis method using Vlife molecular design suits (MDS). Five descriptors showing positive and negative correlation with the β-CAs inhibitory activity have been included in the model. This validated 2D QSAR model may be used to design sulfonamide derivatives with better inhibitory properties.

A Critical Prospect of Structural Designing of Avian Influenza A/H5N1 Neuraminidase Inhibitors That Evade Tamiflu Resistance

The key public health concern is to define the way in which the next influenza pandemic will be controlled. At present, the question of vital importance is: in the absence of a specific avian flu vaccine, could antiviral drugs obstruct a pandemic should the virus spread from birds to humans? The answer to the issue is inevitably related to finding the ways to circumvent Tamiflu resistance that is well documented in the literature. Several remarkable but slightly mutually inconsistent contributions have been recently reported with the aim to facilitate the development of new inhibitors acting on the key target—neuraminidase of avian influenza A/H5N1 virus. Herein, the versatile arguments are critically analyzed and reconciled. Consequently, the most relevant structural basis for the rational design of novel antivirals is elaborated.

Synthesis and Evaluation of Substituted 4,4a-Dihydro-3H,10H-pyrano[4,3-b][1]benzopyran-10-one as Antimicrobial Agent

A series of pyrano[4,3-b][1]benzopyranones (7a–t) were synthesized through hetero-Diels-Alder reaction of substituted 3-formylchromones (5) with enol ethers (6), characterized by IR, 1H NMR, 13C NMR, and mass spectral techniques. All the compounds were evaluated for antimicrobial activity against various bacterial and fungal strains, found to possess significant inhibitory potential, particularly, compounds bearing electron withdrawing group -fluoro such as 7i and 7h. Compounds were also tested and displayed a significant inhibitory potential against methicillin-resistant Staphylococcus aureus (MRSA).

Regioselective Synthesis of Dispiro Pyrrolizidines as Potent Antimicrobial Agents for Human Pathogens

Synthesis of a series of novel dispiro pyrrolizidines has been accomplished by 1,3-dipolar cycloaddition reaction of azomethine ylide generated from secondary amino acids and diketones with bischalcones. These compounds were evaluated for their antibacterial activity. Most of the synthetic compounds exhibited good antibacterial activity against microorganisms.

New Stability Indicating Method for Quantification of Impurities in Amlodipine and Valsartan Tablets by Validated HPLC

A stability indicating LC method was developed for simultaneous determination of amlodipine and valsartan in pharmaceutical dosage form. Efficient chromatographic separation was achieved on C8 stationary phase with simple combination of mobile phase-A (70 : 20 : 10 v/v/v of water : acetonitrile : methanol with 2 mL of Octylamine adjusted the pH to 2.50 + 0.05 with orthophosphoric acid) and mobile phase-B (Acetonitrile) delivered in gradient mode. Quantification was carried out using ultraviolet detection at 240 nm at flow rate of 1.0 mL/min with Injection Volume of 100 μL and ambient column temperature. This method was capable to detect both the drug components of Amlodipine and Valsartan in presence of their degradation products (Amlodipine Imp-A and Valsartan Impurity-B) with the detection level of 0.05%. Amlodipine/Valsartan and their combination drug product were exposed to thermal studies, photolytic, hydrolytic and oxidative stress conditions, and samples analysed. Peak homogeneity data of Amlodipine and Valsartan is obtained using PDA detector, demonstrating the specificity. The method shows excellent linearity over range of 0.05–2.0% for Amlodipine; Amlodipine Impurity-A and 0.05–1.0% for Valsartan and Valsartan Impurity-B. The correlation coefficient for Amlodipine and Valsartan are 0.9999. The proposed method was found to be suitable and accurate for quantitative determination and the stability study of Amlodipine and Valsartan in pharmaceutical preparations.