Determination of Vardenafil in Pure and Dosage Forms by Spectrophotometry

Journal of Applied Spectroscopy - Three simple, sensitive, precise, and rapid spectrophotometric methods are developed and optimized for the assay of vardenafil in pharmaceutical formulations. The...     

Hydromagnetic instability of streaming fluids in porous medium

The instability of the plane interface between two uniform, superposed, electrically conducting and counter-streaming fluids through a porous medium is considered in the presence of a horizontal magnetic field. In the absence of surface tension, perturbations transverse to the direction of streaming are found to be unaffected by the presence of streaming if perturbations in the direction of streaming are ignored. For perturbations in all other directions there exists instability for a certain wavenumber range. The instability of this system is postponed by the presence of magnetic field. The magnetic field and surface tension are able to suppress this Kelvin-Helmholtz instability for small wavelength perturbations and the medium porosity reduces the stability range given in terms of a difference between the streaming velocities and the Alfvén velocity.This research forms a part of the research project awarded to the first author (R.C.S.) by the University Grants Commission.     

Recovery of americium from nitric acid solutions containing calcium by different co-precipitation methods

Recovery of americium from nitric acid solutions was studied by co-precipitation as hydroxide with various ions like calcium, ferric, nickel using sodium hydroxide and ammonium hydroxide. Studies were also carried out to recover americium using lanthanum fluoride and bismuth phosphate co-precipitation. All the methods are able to co-precipitate Am quantitatively. However, co-precipitation of Am with optimum concentration iron using ammonia is found to be better from nitric acid solutions containing large concentrations of calcium ions. Approximately 2 g of Am was recovered from 150 litres of solution batch wise using iron.     

Spectrophotometric determination of uranium(VI) using a synergic mixture of ethyl acetoacetate and pyridine

A method is proposed for the extractive spectrophotometric determination of uranium(VI) using the synergic combination of ethyl acetoacetate (EAA) and pyridine (Py) as extractants. The optimum conditions have been evaluated by varying pH and ethyl acetoacetate and pyridine concentration. The nature of the extracted species has been determined by 1g D-1g C plots and the extracted species was found to be UO₂(EAA)₂.Py. The method has been applied for the separation and determination of uranium(VI) from synthetic mixtures.     

Inhibition of human dihydrofolate reductase by 2,4-diaminoquinazolines bearing simple substituents on the aromatic ring

A series of thirty eight 2,4-diaminoquinazolines having diverse substitution patterns on the aromatic ring was evaluated for inhibitory activity against dihydrofolate reductase (DHFR) obtained from a human lymphoblast cell line. Many of these compounds were also evaluated as inhibitors of rat liver DHFR under the same experimental conditions. In most instances the results obtained with each enzyme were comparable indicating that the rodent enzyme is a suitable model for the human DHFR as far as the determination of I₅₀ values is concerned. The results demonstrate that relatively simple 5-substituted- or 5,6-disubstituted-2,4-diaminoquinazolines can be potent DHFR inhibitors. The presence of a nonpolar substituent at position 7 or 8 was highly detrimental to inhibitory potency.     

Low-molecular weight hyaluronidase from the venom of Bungarus caeruleus (Indian common krait) snake: Isolation and partial characterization

Snake venom hyaluronidases known as “spreading factor” are not extensively studied. Recently, it is argued that beyond its role as a spreading factor, venom hyaluronidase (HYL) deserves to be explored as a possible therapeutic target for inhibiting the systemic distribution of venom/toxins and also for minimizing local tissue destruction. In this context, in the present study, a low-molecular weight HYL has been isolated from Bungarus caeruleus (Indian krait) venom by single step chromatography on HPLC system. The apparent molecular weight determined by SDS-PAGE is 14 ± 2 kDa, as confirmed by zymogen study and LC–MS as well. The enzyme had optimal pH 6 and temperature 37°C. The Michaelis–Menten constant (K_m) was found to be 8.48 µg/mL at 37°C. The activity of purified enzyme was completely inhibited by Ba²⁺ metal ion and N-acetyl imidazole group-specific agents. This work yielded a highly active HYL from B. caeruleus the first one to be isolated. Further studies on its pharmacological actions will be interesting to develop lead molecules for better management of snakebite.     

Polybenzimidazoles: Thermally Stable Materials

Polybenzimidazoles were prepared in poly(phosphoric acid) from isophthalic acid (I), terephthalic acid (T), and 3,3′-di-aminobenzidine tetrahydrochloride dihydrate (DAB). Homo-polymers of I, T, and various IT copolymers have been prepared. The polymers were characterized by viscosity, IR spectra, and nitrogen estimation. The effect of copolymer composition on UV and visible spectra, solubility in various solvents, and density was also investigated. The relative thermal stability of the polymers was evaluated by TGA and DTA.     

Activities of Hydrolases and Oxidases as Influenced by the Application of Monocrotophos in Sandy Loam Soil of Rajasthan

Continuous and repeated use of pesticides affects soil microbial flora and fauna and hence indirectly affects the activity of diverse microbial enzymes present within it. The present study investigates the interaction effect of different concentrations of monocrotophos on diverse hydrolases and oxidases, viz., protease, alkaline phosphatase, acid phosphatase, cellulase, amylase, invertase, arginine deaminase, and dehydrogenase, present in sandy loam soil of Rajasthan under in vitro conditions for 30 days. Soil sample was inoculated with three different concentrations of monocrotophos, viz., 50, 100, and 150 μg kg^-1, and incubated in dark at room temperature. At regular interval of 5 days, sample was withdrawn and enzyme activity was calculated and compared with that of control. Application of various concentrations of monocrotophos enhanced the activity of diverse enzymes present in soil. Therefore, the study revealed synergistic or additive effect of monocrotophos on all the tested microbial enzyme entities. Increasing concentration of the pesticide, however, poses an antagonistic interaction on the increment of different enzymes activities. Therefore, it can be concluded from the study that monocrotophos impose a positive effect at low concentration of pesticide, whereas high concentration poses negative effect on the activity of different enzymes present in soil.