Chemical Methodologies
Volume:3 Issue: 2, May-Apr 2019

A new sensitive, specific, precise and accurate stability indicating reverse phase high performance liquid chromatographic (RP-HPLC) method was developed and validated for the determination of related substances of telmisartan drug substance. The method was developed to separate possible degradation and process related impurities. The method was developed on symmetry shield RP 8 (150 mm x 4.6 mm, 3.5 µm) column using 0.05% trifluoroacetic acid and acetonitrile as mobile phase in gradient elution. The eluents were monitored at 230 nm by UV-Visible detector. Telmisartan and its eleven impurities were well resolved by using these conditions. The limit of detection (LOD) for telmisartan and each of its impurities (Impurity-II, Impurity-III, Impurity-IV, Impurity-V, Impurity-VI, Impurity-VII, Impurity-IX, Impurity-X, Impurity-XI) were 0.01 (% w/w) and that of Impurity-I, Impurity-VIII were 0.02 (% w/w). The limit of quantitation (LOQ) for telmisartan and each of its impuries (Impurity-II, Impurity-III, Impurity-IV, Impurity-V, Impurity-VI, Impurity-VII, Impurity-IX, Impurity-X, Impurity-XI) were 0.03 (% w/w) and that of Impurity-I and Impurity-VIII peaks were 0.05 (% w/w). Forced degradation studies were performed and mass balance was established for acid, base, oxidative, photolytic, thermal and temperature and humidity degradation conditions. The method was validated as per international conference on harmonization of technical requirements for pharmaceuticals for human use (ICH) guidelines. The impurities (Impurity-VI to Impurity XI) were related to route of synthesis and the developed method was capable to quantify these impurities along with impurities (Impurity-I to Impurity-V) as per United States, European pharmacopeia.

An accurate, sensitive, reproducible and precise stability indicating thin layer chromatographic method and UV-Visible spectroscopic method was established for the amelioration and validation of neuroprotective agent edaravone in bulk and its pharmaceutical dosage form. Edaravone injection is used to treat amyotrophic lateral sclerosis (ALS, Lou Gehrig's disease; a condition in which the nerves that control muscle movement slowly die, causing the muscles to shrink and weaken). Edaravone injection is in a class of medications called antioxidants. The high Performance thin layer chromatographic method was developed with proposed chromatographic condition with mobile phase containing n-Hexane: ethyl acetate (7:3, v/v). Accomplishment of UV–Visible spectroscopic determination was done at wavelength maxima of 245 nm using methanol as a solvent. The linearities were in the range of 1-9 µg/ml for UV-Visible spectroscopic method and 100-1400 ng/band for TLC method, respectively. Validation of proposed method has been accomplished with respect to linearity, accuracy, precision, specificity and robustness. For acid and alkali hydrolysis, chemical oxidation, dry heat degradation and photolytic degradation conditions were performed using stock solution of EDA, and quantification which has been achieved by proposed TLC method. Owing to sensitivity, promptness and accuracy of methods, we rely on both intended methods which will be useful for the regular quality control analysis and quantification of drug in bulk and pharmaceutical dosage form.

Graphene is a flat layer of carbon atom, and is a layer of graphite with a thickness of a few tenths of a nanometer that, due to its porous structure and high ionic transfer rate, has been considered in electronic applications, such as cloud storage capacitors with high energy. In this research work, laser-scribed technique has been regarded to synthesize graphene on the surface of a DVD with simples laser equipment and manufacture graphene and graphene composite supercapacitors for the first time without masking. For this purpose, first, by Hummer's method, graphite was converted to graphene oxide (GO) in an acidic environment containing sodium nitrate, potassium permanganate and sulfuric acid. Centrifuges and ultrasonic devices were utilized for the homogenization of graphene oxide solution. GO homogeneous solution was applied on the surface of specific DVDs and the set was dried at room temperature. For GO reduction and its transformation into graphene, a suitable laser, with programming of supercapacitor particular pattern was used. By applying energy with the amount of resonance frequency of graphene and oxygen bond, the laser broke the connection and the reduction in action and reaching to graphene was done. Thus, the optimal wavelength of laser was determined to reduce the GO. In this study, the process of graphene synthesis and applying the supercapacitor specific pattern were carried out in single step that is the biggest advantage of laser-scribed graphene (LSG) method. In present study, TEM was utilized to examine the mono layered structure of GO, SEM was used for microstructural studies of prepared arrays, two tests of cyclic voltammetry (CV) and galvanostatic charge/discharge (CC) were applied to study the performance and power of energy storage in supercapacitors (10 F/g) that six order higher than normal G supercapacitors with repeatability 95% in 10000 cycles, the XPS was used to investigate elements present in the layer applied on DVD, and the Raman spectroscopy was applied to investigate the quality of prepared graphene through studying G and D peaks.

Several agents have been used for the treatment of prostate cancer such as flutamide, galeterone, abiraterone and others; however, some of these drugs can produce some secondary effects. The aim of this study was to synthesize a diaza-bicyclo-naphthalen-oxiranyl-methanone derivative using some chemical tools. The structure of all compounds involved in this study was confirmed by spectroscopy and spectrometry data. In addition, the theoretical interaction of diaza-bicyclo-naphthalen-oxiranyl-methanone derivative with the cytochrome P450-17A1 enzyme (3RUK) was evaluated in a docking model using some drugs such as galeterone and abiraterone as controls. The results showed that diaza-bicyclo-naphthalen-oxiranyl-methanone could interact with different types of amino acid residues involving 3RUK protein surface as compared to both galeterone and abiraterone. This phenomenon may be due to the differences in the chemical structure of compounds. All these data indicate that diaza-bicyclo-naphthalen-oxiranyl-methanone derivative could change the biological activity of cytochrome P450-17A1 enzyme which may be translated as good candidates for prostate cancer.

The aim of present study is to highlight the effects of β-cyclodextrin (BCD) and hydroxypropyl-β-cyclodextrin (HBCD) and also the effect of their concentrations and methods of inclusion complexation on solubility and antibacterial activity of trimethoprim [TMP] by inclusion complex formation. The inclusion complexes of TMP were prepared by solvent evaporation, spray drying, kneading and physical mixture methods in 1:1 and 1:2 ratios. The inclusion complexes were characterized by Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), differential scanning calorimetry (DSC), dissolution study and antimicrobial activity by disk diffusion method. Fourier transform infrared spectroscopy (FT-IR) and X-ray diffraction (XRD) results proved formation of inclusion complex of TEM with cyclodextrins. XRD showed decrease in crystanality of TEM after complexation with CDs. The results of saturation solubility study and release study prevailed the more increase in solubility of TMP by HPCD than BCD. The antibacterial activity of TMP was found to be increased with the complexation process. An increase in concentration of CD increased the dissolution and the antibacterial activity.

A simple, highly efficient and green procedure for the condensation of aryl and alkyl 1,2-diamines with α-diketones in the presence of catalytic amount of boron sulfonic acid (BSA) and silica trimethyl borat (STMB) and silica triisopropyl borate (STIPB), as two novel heterogeneous Lewis acid catalysts at room temperature, is described. In this method, we proved that the BrØnsted acidic power of boron sulfonic acid (BSA) is more important than its Lewis acidity. Using this method, quinoxaline derivatives as biologically interesting compounds are produced in high to excellent yields.

A facile synthesis of eighteen’s novel derivatives of spiro[indole-thiazolidine]diones (5a-5r) has been developed via hitherto unknown schiff bases. In the first step, we alkylated the isatin ring using different alkyl halides in DMF and in the presence of potassium carbonate and tert-butyl ammonium bromide to get 1a-1i. In the second step, N-substituted isatin (1a-1i) reacted with different amine compounds (2a-2f) to get schiff base intermediates (3a-3r). In the third step, cyclocondensation reaction with mercaptoacetic acid afforded a new class of spiro diones. The amine moieties which are used in the second step of this synthesis are varied from aniline derivatives (2a-2d), phenylpyrazole (2e) and oxazole (2f) analogues. Of the 18 final new compounds 9 analogues derived from aniline, 2 analogues derived from oxazole and 7 of them synthesized from phenylpyrazole analogues. Chemical structures of all new compounds were confirmed by spectroscopic methods such as IR, HNMR and CNMR.

MOF-5 has been employed as a powerful catalyst for the preparation of 2-amino-4H-chromene. A wide variety of aromatic aldehydes was condensed with malononitrile and 2-naphthol under mild and solvent-free conditions in the presence of the trace amount of catalyst. A variety of 2-amino-4H-chromene can be obtained in good to excellent yield up to 95% in relatively short time reaction and easy workup.

Vinylene carbonate (VC) is the most well-known additive for current lithium-ion batteries (LIBs). Low anodic stability or insufficient oxidation stability as a drawback of VC affected LIBs performance, especially in high voltage applications. As computational screening is faster and much less expensive than experimental trial and error testing, by using density functional theory (DFT) computations, phthalimide derivatives are screened as promising solid electrolyte interface (SEI) forming additives in LIBs. Our computational screening comprising frontier orbital energy, binding energy, and redox potentials shows that phthalimide derivatives are promising candidates as SEI-forming additives on graphite anode in ethylene carbonate (EC), and propylene carbonate (PC), based electrolytes. Additionally, four phthalimide derivatives including 3-nitrophthalimide, N-chlorophthalimide, 3,4,5,6-tetrachlorophthalimide, and phthalimide itself, due to their higher anodic stability and also reduction potential compared to VC, can be used as future alternatives of VC for LIBs.