Determination of mammalian lignans in biological samples by modified gas chromatography/mass spectrometry

Lignans in flaxseed have been part of the human diet for centuries. In 1955, the isolation and structure of the lignan derivative secoisolariciresinol diglucoside (SDG) was reported. The biological role of SDG and mammalian lignan metabolites enterodiol and enterolactone was initially reported 20 years later. Experimental evidences showed the beneficial effects of lignans on breast, colon, and thyroid cancer. A modified gas chromatography/mass spectrometry (GC/MS) assay was developed for lignans in serum and colon samples of rats fed flaxseed meal. The method developed for the analysis of metabolites involves extraction and derivatization of samples and quantitative analysis by selected ion monitoring using GC/MS. The levels of lignan metabolites enterodiol and enterolactone were determined to be 0.013 and 0.23 microM in serum samples and 0.008 and 1.63 microM in colon samples.     

Rapid resolution of carbohydrate isomers by electrospray ionization ambient pressure ion mobility spectrometry-time-of-flight mass spectrometry (ESI-APIMS-TOFMS)

Carbohydrates are an extremely complex group of isomeric molecules that have been difficult to analyze in the gas phase by mass spectrometry because (1) precursor ions and product ions to successive stages of MS(n) are frequently mixtures of isomers, and (2) detailed information about the anomeric configuration and location of specific stereochemical variants of monosaccharides within larger molecules has not been possible to obtain in a general way. Herein, it is demonstrated that gas-phase analyses by direct combination of electrospray ionization, ambient pressure ion mobility spectrometry, and time-of-flight mass spectrometry (ESI-APIMS-TOFMS) provides sufficient resolution to separate different anomeric methyl glycosides and to separate different stereoisomeric methyl glycosides having the same anomeric configuration. Reducing sugars were typically resolved into more than one peak, which might represent separation of cyclic species having different anomeric configurations and/or ring forms. The extent of separation, both with methyl glycosides and reducing sugars, was significantly affected by the nature of the drift gas and by the nature of an adducting metal ion or ion complex. The study demonstrated that ESI-APIMS-TOFMS is a rapid and effective analytical technique for the separation of isomeric methyl glycosides and simple sugars, and can be used to differentiate glycosides having different anomeric configurations.     

Selective Production of Secondary Amine by the Photocatalytic Cascade Reaction Between Nitrobenzene and Benzyl Alcohol over Nanostructured Bi2MoO6 and Pd Nanoparticles Decorated with Bi2MoO6

The synthesis of secondary amine by the photoalkylation of nitrobenzene with benzyl alcohol using a simple light source and sunlight is a challenging task. Herein, a one-pot cascade protocol is employed to synthesize secondary amine by the reaction between nitrobenzene and benzyl alcohol. The one-pot cascade protocol involves four reactions: (a) photocatalytic reduction of nitrobenzene to aniline, (b) photocatalytic oxidation of benzyl alcohol to benzaldehyde, (c) reaction between aniline and benzaldehyde to form imine, and (d) photocatalytic reduction of imine to a secondary amine. The cascade protocol to synthesize secondary amine is accomplished using Bi₂MoO₆ and Pd nanoparticles decorated Bi₂MoO₆ catalysts. The surface characteristics, oxidation states, and elemental compositions of the materials are characterized by several physicochemical characterization techniques. Optoelectronic and photoelectrochemical measurements are carried out to determine the bandgap, band edge potentials, photocurrents, charge carrier's separation, etc. An excellent yield of secondary amine is achieved with simple household white LED bulbs. The catalyst also exhibits similar or even better activity in sunlight. The structure-activity relationship is established using catalytic activity data, control reactions, physicochemical, optoelectronic characteristics, and scavenging studies. Bi₂MoO₆ and Pd nanoparticles decorated Bi₂MoO₆ exhibit excellent photostability and recyclability. The simple catalyst design with a sustainable and economical light source for the synthesis of useful secondary amine from the nitrobenzene and benzyl alcohol would attract the researchers to develop similar catalytic protocols for other industrially important chemicals.     

Investigating the effect of PEG200 and two-dimensional h-BN on PVDF membrane performance for membrane distillation–crystallization

Although water supplies are prominently dependent on desalination technology, desalination plant facing severe issues of discharged brine concentrate. Membrane distillation crystallization is an emerging synergistic technology that resolves the issue of brine concentrate by recovering clean water and value-added minerals simultaneously. In the present study, properties of polyvinylidene fluoride (PVDF) membrane were modified by incorporation of exfoliated fillers of hexagonal boron nitride and polyethylene glycol. The changes in morphology, surface roughness, hydrophobicity, thermal stability, and chemical composition of the prepared membranes were evaluated by scanning electron microscopy, atomic force microscopy, contact angle, thermogravimetric analysis, Fourier-transform infrared spectroscopy, respectively. Membrane distillation crystallization experiments were conducted to observe the effect of modified membranes on the permeate flux and salts recovery at different feed temperatures. The results showed a significant improvement in the permeate flux with modified membranes compared with pure PVDF membrane. It was found that hexagonal boron nitride/polyethylene glycol200 incorporated PVDF membrane gave the higher permeate flux (3.41 kg/m² h for K₂SO₄ and 2.62 kg/m² h for KNO₃) at a temperature of 80 °C along with higher salts recovery than pure PVDF membranes. A 100 h long run test was conducted on modified membranes, which showed consistency in permeate flux with a marginal increase in conductivity.     

Synthesis of macrocyclic conjugated ψ-disacharides via nitrile oxide cycloaddition: Alkenyl chain length controlled unprecedented formation of di-oxa heterocycles from monosaccharides

Various symmetrical and unsymmetrical isoxazoline embodied chiral macroheterocycles were synthesized from carbohydrate derived oximes. Our result shows that the mode of cycloaddition is dependent on the length and tether present in alkenyl chain of sugar moiety. Thus in some cases inter- and intramolecular cycloaddition of nitrile oxide were observed with high selectivity. The cycloadducts contains two sugar units linked via macrocycles thus they are considered as pseudo-disacharides. The stereochemistry of the newly formed chiral centers was established by 2D-NMR techniques and X-ray crystallographic studies.     

Click chemistry approach for the regioselective synthesis of iso-indoline-1,3-dione-linked 1,4 and 1,5 coumarinyl 1,2,3-triazoles and their photophysical properties

Copper-catalyzed reaction of N-propargyl isoindoline-1,3-dione and 4-azidomethyl coumarins / 4-azidomethyl-1-aza coumarins under click chemistry conditions afforded 1,4-disubstituted 1,2,3-triazoles, whereas ruthenium catalysis yielded isomeric 1,5-disubstituted 1,2,3-triazoles. The two regioisomers have been distinguished by NOE studies. UV absorption for a given pair of isomers exhibited similar trend, whereas fluorescence measurements showed considerable differences. Photo physical studies on the interaction of azides with copper and ruthenium have also been performed.     

Design,synthesis, and antimicrobial evaluation of some nifuroxazide analogs against nosocomial infection

A series of 10 p-substitutedbenzoylmethylene hydrazide derivatives 4a-j were synthesized by protecting carboxylic group of 4-hydroxybenzoic acid using methanol and sulfuric acid than reacting it with hydrazide to form 4-hydroxybenzohydrazide followed by reacting with a variety of aldehydes and evaluated for their activity against nosocomial infection. All the synthesized compounds were characterized by Fourier-transform infrared (FT-IR), ¹H nuclear magnetic resonance (NMR), and mass spectral data. The in vitro antimicrobial potential of synthesized compounds was estimated against prominent strains of nosocomial pathogens (Staphylococcus aureus, Escherichia coli, and Aspergillus niger). The antimicrobial evaluation revealed compounds 4b , 4c , 4d , 4e , 4f , and 4j to be the most active compounds of the series with IC₅₀ value for antibacterial in the range 0.39 to 0.75 μM/mL. Furthermore, the in vitro cytotoxic potential of the compounds was appraised by hemolytic assay. The results showed that some of the synthesized compounds exhibited marked activity.     

Spectroscopic and thermal studies of gamma irradiated polypropylene polymer

Thin films of polypropylene have been irradiated with different doses of gamma radiation from a ⁶⁰Co source. IR, UV-VIS spectra of this polymer before and after irradiation have been recorded and from the spectral data some modifications in the properties have been investigated. The spectra indicated that polypropylene film was oxidised at the dose of 10⁶ Gy. Due to the removal of additives, total destruction of the polymer takes place at this dose. Isotactic arrangement of the polymer is no longer present after irradiation. Growth of carbon cluster takes place above a gamma dose of 10² Gy. Thermal stability of the polymer changes due to irradiation and the polymer seems to decompose in four different steps at the highest dose of 10⁶ Gy.     

Response of Cellulose detectors to different doses of 62?MeV protons

Optical and thermal responses of two cellulose detectors, Cellulose triacetate (Triafol-TN) and Cellulose acetate butyrate (Triafol-BN), to four different doses of 62 MeV protons were studied using spectroscopic, thermal and track-etching techniques. The spectroscopic analysis revealed that though the optical band-gap in the polymers was affected by proton irradiation, the polymers showed high resistance against any major structural modification by radiation. The thermal stability of the polymers was found to be affected by proton irradiation. The activation energy of etching was found to be almost constant for both the polymers even after irradiation. It is hoped that the findings in this work would be of significant relevance to material science and applications of polymers.