Inhibitive properties of a phosphonate-based formulation for corrosion control of carbon steel

The aim of the present work was to study the corrosion inhibition of carbon steel using a ternary formulation. This new ternary inhibitor formulation, viz., 2-phosphonobutane-1,2,4-tricarboxylic acid (PBTC), with zinc ions and silicate ions was used to protect carbon steel from corrosion in a low-chloride environment. The gravimetric studies showed that 96 % inhibition efficiency was achieved with the ternary system consisting of 50 ppm PBTC, 50 ppm Zn²⁺ ions, and 10 ppm silicate ions. Out of 0.310 mmol of Zn²⁺ ions, 0.218 mmol was diffused from the bulk of the solution to the metal surface, as revealed from the studies of the solutions by atomic absorption spectroscopy (AAS). Electrochemical methods (potentiostatic polarization and electrochemical impedance spectroscopy) and surface characterization techniques [Fourier transform infrared (FT-IR), scanning electron microscopy (SEM), and atomic force microscopy (AFM)] were used to ascertain the nature of the protective film and for explaining the mechanistic aspects of corrosion inhibition.     

Improvement of Regio-Specific Production of Myricetin-3-O-α-l-Rhamnoside in Engineered Escherichia coli

Myricetin is an important flavonol whose medically important properties include activities as an antioxidant, anticarcinogen, and antimutagen. The solubility, stability, and other biological properties of the compounds can be enhanced by conjugating aglycon with sugar moieties. The type of sugar moiety also plays a significant role in the biological and physical properties of the natural product glycosides. Reconstructed Escherichia coli containing thymidine diphosphate-α-l-rhamnose sugar gene cassette and Arabidopsis-derived glycosyltransferase were used for rhamnosylation of myricetin. Myricetin (100 μM) was exogenously supplemented to induced cultures of engineered E. coli. The formation of target product—myricetin-3-O-α-l-rhamnoside—was confirmed by chromatographic and NMR analyses. The yield of product was improved by using various mutants and methylated cyclodextrin as a molecular carrier for myricetin in combination with E. coli M3G3. The maximal yield of product is 55.6 μM (3.31-fold higher than the control E. coli MG3) and shows 55.6 % bioconversion of substrate under optimized conditions.     

Synthesis of Active Metabolites of Carvedilol,an Antihypertensive Drug

A simple synthetic route for active metabolites of carvedilol is reported. The metabolites 4′-hydroxycarvedilol and 5′-hydroxycarvedilol have exhibited high activity for β-blockade. We have disclosed syntheses of 4′-hydroxycarvedilol and 5′-hydroxycarvedilol from commercially available vanillin and isovanillin, respectively.     

2,4,5-Tribromo-1H-imidazole in the egg masses of three muricid molluscs

From analysis by gas chromatography/mass spectrometry (GC/MS), the presence of either 2,4,5-tribromo-1H-imidazole (1) or 3,4,5-tribromo-1H-pyrazole (2) was tentatively identified in lipophilic extracts from the egg masses of three muricid molluscs. Synthesis of these compounds, followed by comparison of the GC retention times and fragmentation patterns from electron impact MS, with those of the natural products, indicated that it was 2,4,5-tribromo-1H-imidazole rather than the pyrazole. This imidazole is likely to be responsible for some of the antimicrobial activity observed in the egg extracts. This is the first report of this compound from a natural source.     

Structural and mechanistic studies on ion insertion into the molecular box {[CpCo(CN)3]4[Cp*Ru]4}

The molecular box [CpCo(CN)₃]₄[Cp*Ru]₄ (Co₄Ru₄) reacts readily with a variety of monocations to form M⊂Co₄Ru₄⁺ (M=K⁺, Cs⁺, Rb⁺). Ion competition experiments, monitored by ESI-MS, show that the molecular box binds the smaller K⁺ more rapidly than Cs⁺, but that thermodynamically Co₄Ru₄ prefers the larger ion. The rates of ion-insertion for K⁺ and Cs⁺ into Co₄Ru₄ were found to qualitatively follow second order kinetics with K⁺, 300 M⁻¹ s⁻¹ and Cs⁺, 36 M⁻¹ s⁻¹. The ratio k_K/k_Cs qualitatively matched the ESI-MS results from ion competition experiments. The rates of ion-insertion into Co₄Ru₄ were found to depend on the counter anions. In particular, RbBF₄ reacted with Co₄Ru₄ more slowly than did RbOTf. The slower rates allowed us to establish second order kinetics. ¹H NMR studies reveal that the Cp signal for Co₄Ru₄ is very sensitive to the presence of entering ions, e.g., Rb⁺, whereas the corresponding Cp signal for Rb⊂Co₄Ru₄⁺ was insensitive to the presence of Rb⁺. The molecular structures of [Co₄Ru₄] · 6MeCN, [K⊂Co₄Ru₄]BF₄ · 7MeCN, [Cs⊂Co₄Ru₄]BF₄ · 6MeCN and [Tl⊂Co₄Ru₄]BF₄ · 6MeCN, determined by X-ray diffraction, showed that although the compounds crystallized in the same space group I23, a correlation exists between the Ru-N/Co-C bond distances and the size of the interstitial ion.     

Synthesis and antispasmodic activity evaluation of bis-(papaverine) analogues

A new series of N-substituted bis-(tetrahydropapaverine) ring systems have been synthesised in expectation of better antispasmodic activity in comparison with papaverine. The synthesis of the targeted heterocycles is described along with a discussion of their structure activity relationship. The general synthetic methods of bis-(tetrahydropapaverine) analogues involve tetrahydropapaverine, various piperazines, diisocyanates and diisothiocyanates as starting materials. Pharmacological evaluation involves the in vitro antispasmodic activity on a freshly removed guinea pig ileum using a force displacement transducer amplifier connected to a physiograph. Among the analogues synthesized in the present study, N,N'-bis-[2-carbamoyl-1-(3,4-dimethoxybenzyl)-6,7-dimethoxy-1,2,3,4-tetrahydroisoquinolinyl]piperazine (22), was found to be the most potent muscle relaxant (IC(50): 0.31 microM).     

A Sensitive HPTLC method for Estimation of Swertiamarin in Enicostemma littorale Blume,Swertia chirata (Wall) Clarke,and in formulations containing E. littorale

JPC – Journal of Planar Chromatography – Modern TLC - Swertiamarin is a secoiridoid glucoside present in members of the Gentianaceae family, including Swertia chirata (Wall) Clarke, S....     

Enantiospecific synthesis of ABC-ring system of A-nor and abeo 4(3→2) tetra and pentacyclic triterpenes

Enantiospecific synthesis of ABC-ring systems of A-nor and abeo 4(3→2) tetra and pentacyclic triterpenes has been accomplished starting from the readily available monoterpene (R)-carvone. (R)-Carvone was used as the B-ring of the target molecules. A lithium-liquid ammonia mediated cyclisation of δ,?-unsaturated ester was employed for the cyclopentannulation at the C-5 and C-6 carbons of carvone and an RCM reaction was employed for the cyclohexannulation to generate the ABC-ring system of A-nor tetra and pentacyclic triterpenes. The strategy has been extended for the synthesis of the ABC-ring system of abeo 4(3→2) tetra and pentacyclic triterpenes.     

Validation and clinical application of an LC‐ESI‐MS/MS method for simultaneous determination of tolmetin and MED5, the metabolites of amtolmetin guacil in human plasma

A highly sensitive, rapid assay method has been developed and validated for the simultaneous estimation of tolmetin (TMT) and MED5 in human plasma with liquid chromatography coupled to tandem mass spectrometry with electrospray ionization in the positive‐ion mode. A simple solid‐phase extraction process was used to extract TMT and MED5 along with mycophenolic acid (internal standard, IS) from human plasma. Chromatographic separation was achieved with 0.2% formic acid–acetonitrile (25:75, v/v) at a flow rate of 0.50 mL/min on an X‐Terra RP₁₈ column with a total run time of 2.5 min. The MS/MS ion transitions monitored were 258.1 → 119.0 for TMT, 315.1 → 119.0 for MED5 and 321.2 → 207.0 for IS. Method validation and clinical sample analysis were performed as per FDA guidelines and the results met the acceptance criteria. The lower limit of quantitation achieved was 20 ng/mL and the linearity was observed from 20 to 2000 ng/mL, for both the anlaytes. The intra‐day and inter‐day precisions were in the range 3.27–4.50 and 5.32–8.18%, respectively for TMT and 4.27–5.68 and 5.32–8.85%, respectively for MED5. This novel method has been applied to a clinical pharmacokinetic study. Copyright © 2010 John Wiley & Sons, Ltd.     

A highly sensitive LC‐MS/MS method for the determination of S‐citalopram in rat plasma: application to a pharmacokinetic study in rats

A highly sensitive, rapid assay method has been developed and validated for the estimation of S‐citalopram (S‐CPM) in rat plasma with liquid chromatography coupled to tandem mass spectrometry with electrospray ionization in the positive‐ion mode. The assay procedure involves a simple liquid–liquid extraction of S‐CPM and phenacetin (internal standard, IS) from rat plasma with t‐butyl methyl ether. Chromatographic separation was operated with 0.2% formic acid:acetonitrile (20:80, v/v) at a flow rate of 0.50 mL/min on a Symmetry Shield RP₁₈ column with a total run time of 3.0 min. The MS/MS ion transitions monitored were 325.26 → 109.10 for S‐CPM and 180.10 → 110.10 for IS. Method validation and pre‐clinical sample analysis were performed as per FDA guidelines and the results met the acceptance criteria. The lower limit of quantitation achieved was 0.5 ng/mL and the linearity was observed from 0.5 to 5000 ng/mL. The intra‐ and inter‐day precisions were in the range of 1.14–5.56 and 0.25–12.3%, respectively. This novel method has been applied to a pharmacokinetic study and to estimate brain‐to‐plasma ratio of S‐CPM in rats. Copyright © 2010 John Wiley & Sons, Ltd.