Development of a bioanalytical method for the quantification of sinococuline in human plasma and its application in phase I clinical pharmacokinetic study

A selective, highly sensitive, precise, and novel bioanalytical method has been developed and validated to quantify sinococuline, an active constituent present in the phytopharmaceutical drug product containing Cocculus hirsutus plant extract, in vivo. Chromatographic separation was achieved on a Luna Omega Polar-C18 bonded analytical column maintained at 45°C. The isocratic mobile phase consisted of methanol and ammonium formate buffer (60:40, v/v) at acidic pH with a low flow rate of 0.250 mL/min. Detection was performed on an API 4000 mass spectrometer using electrospray ionization in positive polarity and multiple reaction monitoring mode to achieve a lower limit of quantification of 1.50 ng/mL. Excellent accuracy and precision were obtained after extracting the analyte from plasma samples using a chemical analogue as an internal standard in the absence of an isotope-labeled compound. The extraction efficacy was evidenced from recovery study, and the analyte was found to be stable in plasma. Validation study demonstrated linearity with coefficient of correlation, r ≥ 0.99, and minimal matrix effect. This bioanalytical method was successfully applied to evaluate pharmacokinetic parameters of sinococuline from a phase I clinical trial of an aqueous extract of C. hirsutus in healthy human volunteers.     

Nanoparticles from cationic copolymer and DNA that are soluble and stable in common organic solvents

DNA by virtue of its superlative ability to self-assemble has found use beyond biological research in the design and fabrication of nanomaterials. However, developing novel DNA-based materials for chemical applications might be restricted due to the insoluble nature of DNA in most common organic solvents. In this Communication, we are reporting the first demonstration of making DNA soluble in a variety of nonbiological solvents such as acetonitrile, benzene, dimethyl sulfoxide (DMSO), and tetrahydrofuran with the help of poly(ethylene glycol) (PEG)-based cationic random copolymers. Because of complex formation between cationic copolymer and anionic DNA, nanoparticles are formed. These nanoparticles are expected to exhibit micelle-like structures with a nanometric core of cationic units neutralized by phosphate anions of DNA, surrounded by a shell of PEG segments. As PEG is soluble in the organic solvents used in this study, nanoparticles are stable in these solvents, making entrapped DNA soluble in these organic solvents.     

Design and Development of Zeolite-Based Catalytic Processes for Aromatics Production

Processes for the production of xylenes, which occur in an integrated aromatic complex, are discussed. A brief overview of the work carried out at Indian Petrochemicals Corporation Limited for the development of zeolite-based catalytic processes for the production of aromatics is presented. This includes xylene isomerization, transalkylation and disproportionation of C₇ and C₉ aromatics for maximization of xylenes, selective disproportionation of toluene and selective alkylation of mono-alkylaromatics to p-dialkylbenzene. Achievements in the commercialization of zeolite-based catalysts and processes for isomerization of m-xylene to p- and o-xylene along with dealkylation of ethylbenzene, and for selective ethylation of ethylbenzene to produce p-diethylbenzene are highlighted.     

A convenient synthesis of diaminoglyoxime and diaminofurazan: Useful precursors for the synthesis of high density energetic materials

The reaction of glyoxime ( 4 ) and hydroxylamine hydrochloride in aqueous sodium hydroxide was found to be a safe and inexpensive method for the preparation of multigram quantities of diaminoglyoxime ( 5 ). Potassium hydroxide mediated dehydration of 5 furnished diaminofurazan ( 1 ) in good yield of exceptional purity. The ready availability of 1 and 5 has facilitated the synthesis of new energetic furazan derivative 8 .     

Complexes of poly(ethylene glycol)-based cationic random copolymer and calf thymus DNA: a complete biophysical characterization

Complete biophysical characterization of complexes (polyplexes) of cationic polymers and DNA is needed to understand the mechanism underlying nonviral therapeutic gene transfer. In this article, we propose a new series of synthesized random cationic polymers (RCPs) from methoxy poly(ethylene glycol) monomethacrylate (MePEGMA) and (3-(methacryloylamino)propyl)trimethylammonium chloride with different mole ratios (32:68, 11:89, and 6:94) which could be used as a model system to address and answer the basic questions relating to the mechanism of the interaction of calf thymus DNA (CT-DNA) and cationic polymers. The solubility of the complexes of CT-DNA and RCP was followed by turbidity measurements. It has been observed that complexes of RCP with 68 mol % MePEGMA precipitate near the charge neutralization point, whereas complexes of the other two polymers are water-soluble and stable at all compositions. Dnase 1 digestion experiments show that DNA is inaccessible when it forms complexes with RCP. Ethidium bromide exclusion and gel electrophoretic mobility show that both polymers are capable of binding with CT-DNA. Atomic force microscopy images in conjunction with light scattering experiments showed that the complexes are spherical in nature and 75-100 nm in diameter. Circular dichroism spectroscopy studies indicated that the secondary structure of DNA in the complexes is not perturbed due to the presence of poly(ethylene glycol) segments in the polymer. Furthermore, we used a combination of spectroscopic and calorimetric techniques to determine complete thermodynamic profiles accompanying the helix-coil transition of CT-DNA in the complexes. UV and differential scanning calorimetry melting experiments revealed that DNA in the complexes is more stable than in the free state and the extent of stability depends on the polymer composition. Isothermal titration calorimetry experiments showed that the binding of these RCPs to CT-DNA is associated with small exothermic enthalpy changes. A complete thermodynamic profile showed that the RCP/DNA complex formation is entropically favorable. Much broader opportunities to vary the architecture of the polymers studied here make these systems promising in addressing various basic and practical problems in gene delivery systems.     

Application of high-melting pyridinium salts as ionic liquid catalysts and media for fischer esterification

Pyridinium methanesulfonate (m.p. 185°C) and pyridinium p-toluenesulfonate (m.p. 121°C) were used as catalysts and media for the esterification of carboxylic acids with primary alcohols to give the corresponding esters selectively in high yields. The high melting points of these pyridinium salts did not prevent their application as ionic liquid medium for these reactions which were performed at 90°C.     

Molecular weight and polydispersity estimation of adsorbing polymer brushes by atomic force microscopy

We have estimated the molecular weight, Mn, and polydispersity, PDI, of densely grafted poly(N-isopropylacrylamide) (PNIPAM) brushes using a novel atomic force microscopy (AFM) approach. When compression of a polymer brush induced adsorption of multiple chains to an AFM tip, the resulting decompression force profile exhibited a maximum attractive force at a separation, Lm, that decayed to zero with increasing tip-sample separation. We have found that the separation Lm approximates the average contour length, Lc, determined by gel permeation chromatography (GPC). The detection of a decaying attractive force at separations larger than Lc suggests that chains of above average length sequentially break free from the tip as they are stretched away from the grafting surface. The shape of the decompression profile in this region approximately paralleled the cumulative weight fraction of the grafted chains determined by GPC. The fraction of chains of a given molecular weight determined from a single force curve fit a log-normal distribution, having a standard deviation that provided an estimate of the PDI. We have characterized two PNIPAM brushes by this AFM technique as well as by GPC coupled to a multiangle laser light-scattering detector (MALLS). The values obtained by AFM-(1) Mn,AFM = (3.8+/-0.5) x 10(4), PDI,(AFM) = 1.3+/-0.1 and (2) Mn,AFM = (9.4+/-1.4) x 10(4), PDI,(AFM) = 1.3+/-0.1-agreed quite well with the corresponding GPC/MALLS values of (1) Mn,GPC = 4.77 x 10(4), PDI,GPC = 1.33 and (2) Mn,GPC = 9.49 x 10(4), PDI = 1.35. This technique requires only a single force curve to obtain a statistical distribution of contour lengths and provides a novel method for estimating the Mn and PDI of appropriate uniformly grafted dense polymer layers.     

Treatment of dairy wastewater using a selected bacterial isolate, Alcaligenes sp. MMRR7

Physicochemical and biologic analysis of dairy wastewater showed that the effluent had a high organic load (chemical oxygen demand [COD]: 5095 mg/L), an acidic pH (6.4), and a high probability of coliforms (most probable number [MPN]>1100). The various bacterial strains isolated and purified were identified as Sporolactobacillus sp., Citrobacter sp., Pseudomonas sp., Alcaligenes sp., Bacillus sp., Staphylococcus sp., and Proteus sp., as per the Bergey’s manual of systematic bacteriology. Among the five selected bacterial strains, the strain designated as MMRR₇ and identified as Alcaligenes sp. was found to give a maximum reduction in COD (62%) in 5 d of incubation. Chemical coagulation using alum at a concentration of 0.5 g/100 mL was found to be effective in the primary treatment of the effluent. Studies on free-cell treatment of the coagulated effluent with the selected bacterial strain Alcaligenes sp. MMRR₇ gave a maximum COD reduction of 91% in 120 h. This study clearly indicates the possibility of using Alcaligenes sp. MMRR₇ for the effective treatment of dairy wastewater.     

Evaluation of an atomic force microscopy pull-off method for measuring molecular weight and polydispersity of polymer brushes: effect of grafting density

The accuracy of the molecular weights Mn and polydispersities of polymer brushes, determined by stretching the grafted chains using atomic force microscopy (AFM) and measuring the contour length distribution, was evaluated as a function of grafting density sigma. Poly(N,N-dimethylacrylamide) brushes were prepared by surface initiated atom transfer radical polymerization on latex particles with sigma ranging between 0.17 and 0.0059 chains/nm2 and constant Mn. The polymer, which could be cleaved from the grafting surface by hydrolysis and characterized by gel permeation chromatography (GPC), had a Mn of 30,600 and polydispersity (PDI) of 1.35. The Mn determined by the AFM technique for the higher density brushes agreed quite well with the GPC results but was significantly underestimated for the lower sigma. At high grafting density in good solvent, the extended structure of the brush increases the probability of forming segment-tip contacts located at the chain end. When the distance between chains approached twice the radius of gyration of the polymer, the transition from brush to mushroom structure presumably enabled the formation of a larger number of segment-tip contacts having separations smaller than the contour length, which explains the discrepancy between the two methods at low sigma. The PDI was typically higher than that obtained by GPC, suggesting that sampling of chains with above average contour length occurs at a frequency that is greater than their spatial distribution.