Determination of aldehydes in rainwater using micro-solid-phase extraction and high-performance liquid chromatography

A simple and rapid extraction procedure was developed for determining aldehydes in rainwater samples. This extraction technique involved the use of micro-solid-phase extraction in which the sorbent was held within a polypropylene membrane envelope, followed by high-performance liquid chromatographic analysis. Aldehydes such as formaldehyde, acetaldehyde, propionaldehyde and valeraldehyde were used as model compounds. Extraction conditions were optimized. The method linearity ranged between 0.5 and 50 μg l⁻¹ with the correlation coefficient of 0.987–0.999. The relative standard deviations (RSDs) of the method ranged from 7 to 12%. Method detection limits were in the range of 0.07–0.15 μg l⁻¹, which is lower than those previously reported for solid-phase microextraction combined with gas chromatography–mass spectrometric techniques. The proposed extraction technique was used for determination of aldehydes in rainwater samples to demonstrate the applicability of the method.     

Synthesis of gold nanorods using concentrated aerosol OT in hexane and its application as catalyst for the reduction of eosin

The microemulsion method for the preparation of nanoparticles is well known. We have used the aqueous core of highly concentrated aerosol OT in hexane solution to synthesize gold nanorod by utilizing the aqueous core of surfactant aggregates as host nanoreactor. The shape and size of the aqueous core as well as the particles formed inside the core can be controlled by changing the parameter W₀ (water to surfactant ratio), concentration of gold salt and the concentration of surfactant. When the concentration of the surfactant is very high the shape of the aqueous droplet does not remain spherical but take the shape of prolate. In our study we have made gold nanorods by the reduction of gold chloride with sodium borohydride in the aqueous core of 1 M AOT hexane at a W₀ of 10. The rods are highly monodispersed with a diameter of about 20 nm and a length of 200 nm with an aspect ratio of 10. The absorption spectra of the gold nanorods show two different peaks one at 535 nm and the other at 965 nm. The particles were used as a catalyst for the reduction of eosin with sodium borohydride. The rate constant comes out be very large in comparison with that of uncatalysed reaction. The reaction was carried out at various temperatures between 20 and 60 °C and the activation energy of the reaction was calculated using Arrhenius plot between–ln k and 1/T. The activation energy of the gold nanorods catalysed reaction comes out to be more than two times as compared to uncatalysed reaction.     

Identification of impurities in polymyxin B and colistin bulk sample using liquid chromatography coupled to mass spectrometry

The European Pharmacopoeia (Ph. Eur.) describes liquid chromatography-ultraviolet (LC-UV) methods using C₁₈ stationary phases for the analysis of polymyxin B and colistin.Several unknown impurities were detected in commercial samples of those polypeptide complexes. However, the Ph. Eur. does not specify any related substances for polymyxin B and colistin. Since both methods use non-volatile buffers, the mobile phases were incompatible with mass spectrometry (MS). For the identification of related substances in bulk samples by LC/MS, volatile mobile phase systems were developed. However, the LC/MS methods (with volatile additives) showed inferior chromatographic separation compared to the LC-UV method (with non-volatile additives). Moreover, previously identified impurities by LC/MS could not be assigned in LC-UV methods as the separation in both systems was different.In this study, known impurities were traced in the LC-UV methods and new impurities present in polymyxin B and colistin bulk samples were characterized. To achieve this, each peak from the non-volatile system was collected separately and reinjected into an LC system with a volatile mobile phase coupled to MS. This way, collected impurity peaks were rechromatographed on a reversed phase column in order to separate the analyte from the buffer salts. Using this method, out of 39 peaks, five novel related substances were characterized in a polymyxin B bulk sample. Fourteen impurities, which were already reported in the literature were traced as good as possible in the LC-UV method. In the case of colistin, a total of 36 peaks were investigated, among which four new compounds. Additionally, 30 known impurities were traced in the LC-UV method.     

Simple, sensitive, selective and validated spectrophotometric methods for the estimation of a biomarker trigonelline from polyherbal gels

Simple, accurate, reproducible, selective, sensitive and cost effective UV-spectrophotometric methods were developed and validated for the estimation of trigonelline in bulk and pharmaceutical formulations. Trigonelline was estimated at 265 nm in deionised water and at 264 nm in phosphate buffer (pH 4.5). Beer's law was obeyed in the concentration ranges of 1-20microg mL(-1) (r2=0.9999) in deionised water and 1-24 microg mL(-1) (r2=0.9999) in the phosphate buffer medium. The apparent molar absorptivity and Sandell's sensitivity coefficient were found to be 4.04 x 10(3)L mol(-1)cm(-1) and 0.0422 microg cm(-2)/0.001A in deionised water; and 3.05 x 10(3)L mol(-1)cm(-1) and 0.0567 microg cm(-2)/0.001A in phosphate buffer media, respectively. These methods were tested and validated for various parameters according to ICH guidelines. The detection and quantitation limits were found to be 0.12 and 0.37 microg mL(-1) in deionised water and 0.13 and 0.40 microg mL(-1) in phosphate buffer medium, respectively. The proposed methods were successfully applied for the determination of trigonelline in pharmaceutical formulations (vaginal tablets and bioadhesive vaginal gels). The results demonstrated that the procedure is accurate, precise, specific and reproducible (percent relative standard deviation <2%), while being simple and less time consuming and hence can be suitably applied for the estimation of trigonelline in different dosage forms and dissolution studies.     

Recent advancement in the synthesis of phenoxazine derivatives and their analogues

In recent years, angular and linear phenoxazines and their derivatives and polymers have attracted much attention due to their great pharmacological and industrial utility. So it becomes imperative to review the work done in this area more frequently. Therefore, various synthetic routes for phenoxazines are reviewed here comprehensively.     

Development of a liposome-based immunochromatographic strip assay for the detection of Salmonella

Salmonella species are ubiquitous human pathogens which pose a dangerous threat to the elderly and children worldwide. In this study, to develop a more efficient assay procedure for the rapid detection of Salmonella Typhimurium, an immunochromatographic strip assay was developed using immunoliposome (anti-Salmonella IgG-tagged) encapsulated with sulforhodamine B (SRB). The detection sensitivity of the developed immunochromatographic assay was compared with a commercial immunochromatographic test strip using colloidal gold nanoparticles. The liposomes were prepared through a reverse-phase evaporation method by using a lipid and phospholipid mixture and SRB, a fluorescence dye, which was encapsulated in the phospholipid bilayer. Furthermore, the outer surface of the SRB-encapsulated liposome was conjugated with antibody (affinity-purified polyclonal goat anti-Salmonella IgG) to form an immunoliposome (size, 223 nm), used as the analytical reagent in the developed immunoassay. For this strip assay, a plastic-backed nitrocellulose strip was immobilized with two antibody zones. The lower zone of the strip referred to Salmonella antigen capture zone (test line), while the other zone served as a positive control (control line). The lower zone was coated with affinity-purified polyclonal goat anti-Salmonella IgG, while the upper zone was coated with rabbit anti-goat IgG. During capillary migration of the wicking solution (diluted liposome and Salmonella culture, each 50 μl), Salmonella was captured with surface-bound immunoliposomes at the antigen capture zone, while the unbound liposomes migrated upward and bound to another zone. The color density of the antigen capture zone was directly proportional to the amount of S. Typhimurium in the test sample. As a result, the detection limit of the immunochromatographic strip assay developed in this study against S. Typhimurium was found to be 10² CFU/ml, which was significantly higher than the detection limit (10⁷ CFU/ml) of the commercial immunochromatographic test strip assay.     

Marker-based standardization of polyherbal capsule formulation by high-performance thin-layer chromatography (HPTLC)–densitometric method using andrographolide and catechin

Himalaya PartySmart capsule is a polyherbal formulation recommended for its liver-protective properties. As the formulation contains extracts of six different herbs, a large number of markers are present in the same. This research work reports the standardization of Himalaya PartySmart capsule using andrographolide and catechin as therapeutic phytoconstituents to assess its quality and efficacy. A specific, sensitive, precise, and accurate high-performance thin-layer chromatography (HPTLC) method has been developed for the quantitative estimation of andrographolide and catechin. Separation was performed on TLC silica gel 60 F₂₅₄ aluminum plates as the stationary phase using chloroform‒acetone‒formic acid (7:3:0.5, V/V) as the mobile phase with densitometric detection at 259 nm. The developed method was validated as per the recommendations of the International Council for Harmonisation (ICH) Q2(R1) guideline. Each marker phytoconstituent showed a good linear relationship with an average correlation coefficient (r²) = 0.99 in the concentration range studied. The proposed method was found to be specific, precise, and accurate with recovery within the range of 95‒105% and hence can be used for the routine analysis of PartySmart capsule formulation.

     

Association of Acenaphthoporphyrins with Liposomes for the Photodynamic Treatment of Leishmaniasis

Acenaphthoporphyrins are potential photosensitizers for photodynamic therapy, but their hydrophobicity limits their potential. Liposomes have been widely investigated as delivery vehicles that can transport hydrophobic drugs in biological systems. Here we study the association of acenaphthoporphyrins with liposomes made up of dimyristoyl phosphatidylcholine (DMPC), and to liposomes made up of a mixture of DMPC, cholesterol (Chol) and distearoyl phosphatidylglycerol (DSPG) in a 2:1:0.8 molar ratio to evaluate how liposome composition affects association constants. In liposomes consisting only of DMPC, the smaller monoacenaphthoporphyrin had the largest association constant of 5.5 × 10⁴ m ⁻¹ while the larger adj-diacenaphthoporphyrin and opp-diacenaphthoporphyrin (ODP) had smaller association constants at 1.8 × 10⁴ and 1.5 × 10⁴ m ⁻¹, respectively. The addition of liposomal Chol and DSPG has little effect on the magnitudes of the association constants. Polarization studies show that the acenaphthoporphyrins are driven far into the lipid bilayer to minimize polar–nonpolar interactions. Confocal microscopy confirms that the DMPC liposomes transport the porphyrins into promastigotes of Leishmania tarentolae. The compounds associated with DMPC:Chol:DSPG liposomes are effective in vitro against axenic and intracellular amastigotes of the pathogenic Leishmania panamensis. The effectiveness of the compounds is enhanced upon exposure of cultures to visible light.     

Cellular uptake of an α-AApeptide

Some short and cationic peptides such as the Tat peptide can cross the cell membrane and function as vectors for intracellular delivery. Here we show that an α-AApeptide is able to penetrate the membranes of living cells from an extracellular environment and enter the endosome and cytoplasm of cells. The efficiency of the cellular uptake is comparable to a Tat peptide (48-57) of the same length and is unexpectedly superior to an α-peptide with identical functional groups. The mechanism of uptake is similar to that of the Tat peptide and is through endocytosis by an energy-dependent pathway. Due to the easy synthesis of the α-AApeptides, their resistance to proteolytic hydrolysis, and their low cytotoxicity, α-AApeptides represent a new class of transporters for the delivery of drugs.