Virtual Combinatorial Library Design, Synthesis and In vitro Anticancer Assessment of -2-Amino-3-Cyanopyridine Derivatives.

AIM AND OBJECTIVE: For the development of new class of anticancer agents, a series of novel 2-amino-3-cyanopyridine derivatives were designed from virtual screening with Glide program by setting Topoisomerase II as the target. MATERIALS AND METHODS: The top ranked ten molecules from the virtual screening were synthesized by microwave assisted technique and investigated for their cytotoxic activity against MCF-7 and A- 549 cell lines by using sulforhodamine B assay method. RESULTS: The most active compound 2-amino-4-(3,5-dibromo-4-hydroxyphenyl)-6-(2,4- dichlorophenyl) nicotinonitrile (CG-5) showed significant cytotoxic profile with (LC50 = 97.1, TGI = 29.9 and GI50 = <0.1 µM) in MCF-7 and (LC50= 93.0, TGI= 50.0 and GI50= <7 µM) in A-549 cell lines. A molecular docking study was performed to explore the binding interaction of CG-5with the active site of Topoisomerase II. CONCLUSION: It can be concluded that halogen substituent pyridine ring was benefit for cytotoxicity.

Discovery of Camptothecin Based Topoisomerase I Inhibitors: Identification Using an Atom Based 3D-QSAR, Pharmacophore Modeling, Virtual Screening and Molecular Docking Approach.

BACKGROUND: Camptothecin is a quinoline alkaloid, isolated from the Chinese tree Camptotheca acuminate which exhibits its cytotoxic activity by the inhibition of nuclear enzyme Topoisomerase I (topo I). Camptothecin and its analogues forms a covalent bond with DNA which can arrest the tumor growth by slowing the religation step of the enzyme and stabilize the covalent adduct between topo I and DNA. Besides its strong anticancer potential, the limited solubility as well as instability of the hydroxylactone ring (Ring E) limits the clinical application of Camptothecin. This study was undertaken to identify novel compounds having anticancer activity with mechanism of action similar to that of Camptothecin using scaffold perception technique. MATERIALS AND METHODS: We developed a common pharmacophore hypothesis using 32 camptothecin analogues, which was used for preliminary screening of large databases (ZINC "drug-like" database) to make sure, to include only compounds containing the key structural features needed to be Topoisomerase I inhibitors. In terms of a structure based approach, we systematically investigated various types of docking protocols to identify the most active compounds from the identified hit molecules. A post docking energy calculation was also carried out by MM/GBSA method. RESULTS: From the selected series of camptothecin analogs, a 3D-QSAR pharmacophore model was developed. The model consists of one acceptor site, one donor site, one hydrophobic site and two aromatic functions (ADHRR). Then, the pharmacophore model was employed as 3D search query to screen compounds from ZINC database which followed by molecular docking study and MM/GBSA calculation identified 2 lead molecules which, however, were not biologically validated. In silico studies reveals that the identified lead molecules have a better binding affinity than the co crystallized ligand. CONCLUSION: The identified molecules were able to bind to the active site of Topo-I enzyme similar to that of Camptothecin and the ADME properties were within the acceptable range defined for human use. The new molecules identified by virtual screening as such or on further optimization can be used as potential leads in designing Topoisomerase I inhibitors.

Establishment of inherent stability of pramipexole and development of validated stability indicating LC-UV and LC-MS method.

Pramipexole belongs to a class of nonergot dopamine agonist recently approved for the treatment of early and advanced Parkinson's disease. A validated specific stability indicating reversed-phase liquid chromatographic method has been developed for the quantitative determination of pramipexole in bulk as well as in pharmaceutical dosage forms in the presence of degradation products. Forced degradation studies were performed by exposition of drug to hydrolytic (acidic and basic), oxidative and photolytic stress conditions, as defined under ICH guideline Q1A (R2). Significant degradation was observed under hydrolytic, oxidative and photolytic conditions and the degradation products formed were identified by LC-MS.

Stress studies of tenofovir disoproxil fumarate by HPTLC in bulk drug and pharmaceutical formulation.

A stability-indicating high-performance thin-layer chromatographic (HPTLC) method for determination of tenofovir disoproxil fumarate in bulk drug and in tablet has been developed and validated. The mobile phase selected was chloroform:methanol (9.0:1.0, v/v) with ultraviolet (UV) detection at 260 nm. The retention factor was found to be 0.49 ± 0.03 with correlation coefficients of 0.9994 in the range 300-1500 ng/spot and with an accuracy of 99.25%. Method had the potential to determine tenofovir disoproxil fumarate from tablet without any interference, and it was a stability-indicating one.

LC-UV and LC-MS evaluation of stress degradation behavior of desvenlafaxine.

The objective of current study was to develop a validated specific stability indicating reversed-phase liquid chromatographic method for the quantitative determination of desvenlafaxine in bulk sample and pharmaceutical dosage form in the presence of degradation products. Forced degradation studies were performed on bulk sample of desvenlafaxine as per ICH prescribed stress conditions using acid, base, oxidative and photolytic degradation to show the stability indicating power of the method. Significant degradation was observed under acidic stress condition and the degradation product formed was identified by LC-MS and a degradation pathway for drug has been proposed. Successful separation of drug from degradation products formed under stress conditions was achieved on a SymmetryShield column C18 (5 µm, 250 mm×4.6 mm, i.d.) using the mobile phase consisting of a mixture of 0.2% (v/v) triethylamine in ammonium acetate (0.05 M; pH 6.5) and methanol using isocratic gradient.

Validated RP-HPLC Method for Simultaneous Quantitation of Losartan Potassium and Metolazone in Bulk Drug and Formulation.

A HPLC method has been described for simultaneous determination of Losartan potassium and Metolazone in formulation. This method is based on a HPLC separation of the two drugs on the Thermo Hypersil BDS-C(18) (250 mm × 4.6 mm, 5.0 µm) with isocratic conditions and a simple mobile phase containing acetonitrile:water (60:40) at a flow rate of 0.8 mL/min using UV detection at 237 nm. This method has been applied to a marketed formulation without interference of excipients. The linear regression analysis data for the calibration plots showed a good linear relationship over the concentration range of 2-12 µg/mL for Losartan potassium and 0.2-1.2 µg/mL for Metolazone, respectively. The method was validated for precision, robustness and recovery. Statistical analysis showed that the method is repeatable and selective for the estimation of Losartan potassium and Metolazone.

Validated HPTLC method for simultaneous quantitation of paracetamol, diclofenac potassium, and famotidine in tablet formulation.

A sensitive, simple, selective, precise, and accurate HPTLC method of analysis for paracetamol, diclofenac potassium, and famotidine both as a bulk drug and in tablet formulation was developed and validated. The method used HPTLC aluminum plates precoated with silica gel 60F254 as the stationary phase, and the mobile phase consisted of toluene-acetone-methanol-formic acid (5 + 2 + 2 + 0.01, v/v/v/v). Densitometric evaluation of the separated zones was performed at 274 nm. This system was found to give compact spots for paracetamol (Rf value = 0.62 +/- 0.03), diclofenac potassium (0.75 +/- 0.02), and famotidine (0.17 +/- 0.03). The linear regression analysis data for the calibration plots showed a good linear relationship over the concentration range of 1625-9750 ng/spot for paracetamol, 250-1500 ng/spot for diclofenac potassium, and 100-600 ng/spot for famotidine. The method was validated for precision, robustness, and recovery according to International Conference on Harmonization guidelines. No chromatographic interference from the tablet excipients was found. Statistical analysis showed that the method was repeatable and selective for the simultaneous quantitation of the three drugs in tablet formulation and for routine quality control of raw materials of the drugs.

Application of a stability-indicating thin-layer chromatographic method to the determination of tenatoprazole in pharmaceutical dosage forms.

A sensitive, selective, precise, and stability-indicating thin-layer chromatographic (TLC) method was developed and validated for the determination of tenatoprazole both as a bulk drug and in formulation. The method uses TLC aluminum plates precoated with Silica Gel 60F-254 as the stationary phase and the solvent system toluene-ethyl acetate-methanol (6 + 4 + 1, v/v/v). This system gave compact spots for tenatoprazole (Rf value of 0.34 +/- 0.02). Tenatoprazole was subjected to acid and alkali hydrolysis, oxidation, and photodegradation. The peaks of the degradation products were well-resolved from that of the pure drug and had significantly different Rf values. Densitometric analysis of tenatoprazole was performed in the absorbance mode at 306 nm. The linear regression analysis data for the calibration plots showed a good linear relationship over the concentration range of 100-1500 ng/spot. The mean values of the correlation coefficient, slope, and intercept were 0.9989 +/- 1.42, 10.27 +/- 0.965, and 4894.2 +/- 1.24, respectively. The method was validated for precision, robustness, and recovery. The limit of detection and limit of quantitation were 50 and 100 ng/spot, respectively. Statistical analysis showed that the method is repeatable and selective for estimation of tenatoprazole. Because the method can separate the drug from its degradation products, it can be used to monitor stability.

Column liquid chromatography-ultraviolet and column liquid chromatography/mass spectrometry evaluation of stress degradation behavior of escitalopram oxalate.

The objective of this work was to study the degradation behavior of escitalopram oxalate under different International Conference on Harmonization (ICH)-recommended stress conditions by column liquid chromatography (LC)-UV and LC/mass spectrometry (LC/MS) and to establish a validated stability-indicating LC assay method. Escitalopram oxalate was subjected to stress conditions of hydrolysis, oxidation, photolysis, and thermal decomposition. Extensive degradation was found to occur in alkaline medium. Mild degradation was observed in acidic and oxidative conditions. Escitalopram oxalate was stable to neutral, photolytic, and thermal stress. Successful separation of the drug from degradation products formed under stress conditions was achieved on a PerfectSil-100 ODS-3 column [C18 (5 microm, 25 cm x 4.6 mm id)] using methanol-0.01 M acetate buffer pH 3.8 adjusted with acetic acid (45 + 55) as the mobile phase. The flow rate was 1 ml/min, and the detection wavelength was 239 nm. The method was validated according to ICH guidelines. Major degradation products formed in hydrolysis and oxidative conditions were isolated, and structural elucidation of degradation products was done by LCIMS and infrared spectrometry studies. The major hydrolysis degradation product was confirmed as 1-(3-dimethylaminopropyl)-1-(4-fluoro- phenyl)-1,3dihydroisobenzofuran-5-carboxylic acid, and the major oxidative degradation product was confirmed as 1-{[3-dimethylamino(oxide)- propyl]-1-(4-fluro-phenyl)}-1,3-dihydro-isobenzofuran- 5-carbonitrile.