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Abstract  

Derivative of 8-hydroxyquinoline i.e. Clioquinol is well known for its antibiotic properties, drug design and coordinating ability towards metal ion such as Copper(II). The structure of mixed ligand complexes has been investigated using spectral, elemental and thermal analysis. In vitro anti microbial activity against four bacterial species were performed i.e. Escherichia coli, Pseudomonas aeruginosa, Serratia marcescens, Bacillus substilis and found that synthesized complexes (15–37 mm) were found to be significant potent compared to standard drugs (clioquinol i.e. 10–26 mm), parental ligands and metal salts employed for complexation. The kinetic parameters such as order of reaction (n = 0.96–1.49), and the energy of activation (E a = 3.065–142.9 kJ mol−1), have been calculated using Freeman–Carroll method. The range found for the pre-exponential factor (A), the activation entropy (S* = −91.03 to−102.6 JK−1 mol−1), the activation enthalpy (H* = 0.380–135.15 kJ mol−1), and the free energy (G* = 33.52–222.4 kJ mol−1) of activation reveals that the complexes are more stable. Order of stability of complexes were found to be [Cu(A4)(CQ)OH] · 4H2O > [Cu(A3)(CQ)OH] · 5H2O > [Cu(A1)(CQ)OH] · H2O > [Cu(A2)(CQ)OH] · 3H2O

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The effect of exogenous application of growth regulators (IAA, NAA, GA3 and BAP) on xylogenesis has been investigated in actively growing shoots of Leucaena leucocephala by anatomical methods. Auxins are (both IAA and NAA) found to be the key regulators of differentiation of narrow lumen vessels and tracheids. These elements were derived not only from fusiform cambial cells, but also from axial parenchyma through transdifferentiation. The exogenous feeding of GA3 induced differentiation of gelatinous fibres, deformed vessels, elongated thin walled fibres and a high fibre/vessel ratio. BAP application decreased the cambial activity and cell differentiation process resulting in development of thick walled fibres and vessel elements, and also delayed lignification of cell walls. The application of combination of hormones showed both synergistic and antagonistic nature of interaction among different hormones. Combination of GA3 and auxins induced cambial cell division and relatively fast differentiation of xylem, while increasing concentrations of GA3 over auxins induced differentiation of gelatinous fibres. The combination of high concentration of BAP either with auxins or with GA3 slowed down cambial activity and xylem differentiation. Moderate concentrations of BAP and GA3 induced gelatinous fibres with thick gelatinous layer indicating the synergistic effect of both hormones.

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Summary

A new, simple, and rapid high-performance thin-layer chromatographic method has been established for quantitative analysis of risperidone. Chromatography was performed on silica gel 60 F254 plates with methanol-ethyl acetate 8.0:2.0 (v/v) as mobile phase. Risperidone was quantified by densitometric analysis at 285 nm. The method gave compact bands for the drug (R F 0.34 ± 0.01). Linear regression analysis of calibration data revealed a good linear relationship (r 2 = 0.9996) between response and amount of risperidone in the range 100–600 ng per band. The method was validated for precision, recovery, repeatability, linearity, specificity, and robustness in accordance with ICH guidelines. The minimum detectable amount was 22.44 ng per band and the limit of quantification was 68.01 ng per band. Statistical analysis of the results showed the method enabled precise, accurate, reproducible, and selective analysis of risperidone. The method was successfully used for estimation of the equilibrium solubility of risperidone, and for quantification of risperidone as the bulk drug in a commercially available preparation, in in-house-developed mucoadhesive microemulsion formulations, and in solution.

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Transition metal complexes with uninegative bidentate Schiff base

Synthetic, thermal, spectroscopic and coordination aspects

Journal of Thermal Analysis and Calorimetry
Authors: C. K. Modi, S. H. Patel, and M. N. Patel

Abstract

The present article describes the synthesis, structural features and thermal studies of the complexes of the type [M(SB)2(H2O)2nH2O [where HSB=pyridine-m-carboxaldene-o-aminobenzoic acid and M=Mn(II), Co(II), Ni(II), Cu(II), Zn(II) and Cd(II)]. The complexes have been characterized on the basis of elemental analyses, magnetic susceptibility measurements, (FTIR and electronic) spectra and thermal studies. The nature of the bonding has been discussed on the basis of infrared spectral data. Magnetic susceptibility measurements and electronic spectral data suggest a six-coordinated structure of these complexes. The complexes of Mn(II), Co(II), Ni(II), Cu(II) are paramagnetic, while Zn(II) and Cd(II) are diamagnetic in nature.

The thermal decomposition of the complexes have been studied and indicates that not only the crystallization and coordinated water are lost but also that the decomposition of the ligand from the complexes is necessary to interpret the successive mass losses. The kinetic parameters such as order of reaction (n) and the energy of activation (E a) have been reported using Freeman–Carroll method. The entropy (S*), the pre-exponential factor (A), the enthalpy (H*) and the Gibbs free energy (G*) have been calculated.

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Abstract  

A new and simple method for selective spectrophotometric determination of uranium(VI) with 4-(2-pyridylazo)resorcinol (PAR) and N-octylacetamide into benzene over pH 7.0–9.0 is described. The molar absorptivity of the complex with 9 different amides is in the range of (0.40–3.2)·104 1·mol–1·cm–1 at the absorption maximum. Out of these, the most sensitive compound N-octylacetamide (OAA) was chosen for detailed studies in the present investigation. The detection limit of the method is 0.008 g U·ml–1. The system obeys Beer's law in the range of 0–5 g U·ml–1. The method is free from interferences of most of the common metal ions except vanadium(V) and copper(II), which are masked by proper masking agents. The composition of the complex is determined by curve-fitting method. The method has been applied for the recovery of the metal from rock samples and synthetic mixtures.

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In the present study, a design-of-experiment (DoE) approach Was used to determine optimized mobile-phase compositions for the development of a high-performance thin-layer chromatography (HPTLC) method for the simultaneous estimation of berberine chloride (BER-H) and galangin (GAL) in Tinospora cordifolia M. and Alpinia galanga L., respectively, and their formulations. A Box‒Behnken design (BBD) was used to optimize the compositional parameters and evaluate the main effect, interaction effects and quadratic effects of the mobile-phase compositions on the retardation factor (R F) of both drugs. HPTLC separation was performed on aluminum plates pre-coated with silica gel 60 F254 as the stationary phase, using toluene‒ethyl acetate‒formic acid (3:6:1, v/v) as the mobile phase at a wavelength of 267 nm. A sharp and well-resolved peak was obtained for BER-H and GAL at R F values of 0.17 ± 0.01 and 0.82 ± 0.01, respectively. The calibration curve was in the range of 200–1200 ng per band for both BER-H and GAL, with r 2 = 0.984 and r 2 = 0.980, respectively. Statistical insight was achieved with analysis of variance (ANOVA). The method was validated for linearity, accuracy, precision, limit of detection, limit of quantification, robustness, and specificity. To provide a better visualization of the statistically significant factors derived from the statistical analysis, the perturbation plot and response surface plot for the effect of independent variables on the R F of BER-H and GAL were evaluated. The developed HPTLC method was found to be simple, accurate, precise, sensitive, and specific for the simultaneous quantification of berberine chloride and galangin in Tinospora cordifolia M. and Alpinia galanga L., respectively, and their formulations.

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This work represents the validation of a stability-indicating thin-layer chromatographic technique for the simultaneous estimation of metolazone (METO) and spironolactone (SPIRO) from marketed formulation (tablets). Thin-layer chromatography was performed using precoated silica gel plate 60 F254 using ethyl acetate—chloroform—GAA (5:5:0.1 v/v) as the mobile phase for the separation of METO and SPIRO. The stability study forms an integral part of the formulation development process, and its use is also encouraged by various guidelines. Stress study was performed on active pharmaceutical ingredients (APIs) as well as on formulation for establishing a stability-indicating thin-layer chromatographic method for both drugs. The APIs were subjected to change under various environmental conditions such as pH, temperature, oxidation, etc. to determine their effect on the stability of drugs. The developed method was able to resolve drugs and their degradation products formed under the aforementioned conditions. The wavelength selected for quantitation was 238 nm. The method was validated as per the International Conference on Harmonization (ICH) guidelines and found to be linear in the range of 50–300 ng spot−1 for METO and 200–1200 ng spot−1 for SPIRO. The relative standard deviation (% RSD) values of the precision study were <2% which indicated that the developed method was precise; recovery was found to be 99.02–100.58% and 99.26–100.17% for METO and SPIRO, respectively. It could be concluded from the stability study that METO was prone to acidic hydrolysis and photolysis while SPIRO was prone to alkaline degradation.

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Summary

In the present study, a design of experiment (DoE) approach was used to optimize chromatographic conditions for the development of a high-performance thin-layer chromatography (HPTLC) method for the simultaneous estimation of metformin hydrochloride (MET) and ursodeoxycholic acid (URSO) in pharmaceutical dosage form. The critical factors were identified using a Taguchi design, and after identification of critical factors, optimization was done using Box-Behnken design (BBD). BBD was used to optimize the compositional parameters and to evaluate the main effect, interaction effects, and quadratic effects of the mobile phase compositions, development distance, and saturation time on the retardation factor (R F) of both drugs. HPTLC separation was performed on aluminum plates pre-coated with silica gel 60 F254 as the stationary phase, using toluene–ethanol–acetone–formic acid (4.5:2:2.5:0.85, V/V) as the mobile phase at a wavelength of 234 nm and 700 nm for MET and URSO, respectively. A sharp and well-resolved peak was obtained for MET and URSO at R F values of 0.19 and 0.80 min, respectively. The calibration curve was in the range of 5000–40000 ng per spot and 1500–12000 ng per spot for MET and URSO, with r 2 = 0.984 and r 2 = 0.980, respectively. The method was validated for linearity, accuracy, precision, limit of detection, limit of quantification, and specificity. To provide a better visualization of the statistically significant factors derived from the statistical analysis, the perturbation plot and response surface plot for the effect of independent variables on the R F of MET and URSO were evaluated. Stability study was performed under different stress conditions such as acid and alkali hydrolysis, oxidation, and temperature. The developed method was able to resolve drugs and their degradation products formed under the afore-mentioned conditions.

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Summary

A simple, specific, accurate, and precise high-performance thin-layer chromatographic method for analysis of aceclofenac and paracetamol in combined tablet dosage forms is reported in this paper. The method uses aluminium plates coated with silica gel 60 F254 as stationary phase and ethyl acetate-n-butanol-glacial acetic acid 7.5:2.5:0.005 (v/v) as mobile phase. Densitometric evaluation of the separated bands was performed at 270 nm. The two drugs were satisfactorily resolved with R F values 0.29 ± 0.019 and 0.74 ± 0.025 for aceclofenac and paracetamol, respectively. The respective calibration plots were linear over the ranges 50–1000 and 200–1500 ng per band. Intra-day variation, as RSD (%), was 0.420 ± 0.282 for aceclofenac and 0.354 ± 0.212 for paracetamol. Interday variation, as RSD (%) ± SE, was 0.57 ± 0.41 for aceclofenac and 0.90 ± 1.09 for paracetamol. The method, which was validated in accordance with ICH guidelines, can be used for analysis of ten or more formulations on a single plate and is a rapid and cost-effective quality-control tool for routine simultaneous analysis of aceclofenac and paracetamol in combined dosage forms.

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