Combinatorial synthesis, reversed-phase and normal-phase high-performance liquid chromatography elution data and liquid chromatography/positive atmospheric pressure chemical ionization tandem mass spectra of methoxylated and glycosylated resveratrol analogues

Analyses of methoxylated and glycosylated stilbenes remain scarce in the literature because of the commercial unavailability of these compounds. Here a library of 22 compounds was synthesized by combinatorial chemistry. Their elution profiles were compared on three different columns (C18, C8, and silica) with those of seven commercial resveratrol analogues and two viniferins. The spectra recorded by liquid chromatography/positive atmospheric pressure chemical ionization tandem mass spectrometry (LC-APCI(+)-MS/MS) are discussed and recommendations made for easier identification of new stilbenes.     

Metal-chelating nanoparticles as selective fluorescent sensor for Cu2+

A fluorescent sensor for Cu(2+) at the nanomolar level in water has been designed by associating a BODIPY fluorophore and a selective ligand (cyclam) in ultrafine polymer nanoparticles.     

Easy access to diastereomerically pure platinacycles

The synthesis of the first examples of diastereomerically pure platinacycles having simultaneously a chiral carbon and a sigma[Pt-C(sp(2), ferrocene)] bond is described.     

Liquid-phase microextraction with in-drop derivatization combined with microvolume fluorospectrometry for free and hydrolyzed formaldehyde determination in textile samples

A new miniaturized methodology based on the combination of headspace single drop microextraction and microvolume fluorospectrometry is proposed in this work for the determination of free and hydrolyzed formaldehyde in textile samples. The proposed method is based on the extraction and in-drop derivatization of free and hydrolyzed formaldehyde using the Hantzsch reaction. The effect of experimental variables affecting the performance of the proposed method, such as fluorescence parameters, nature of the extractant phase composition (including acetylacetone concentration, pH, ammonium acetate concentration and presence of an organic solvent), sample temperature, NaCl concentration and microextraction time was carefully investigated. Under optimized conditions, instrumental detection and quantification limits were 26 and 87 μg L⁻¹, respectively, whereas procedural detection and quantification limits were 1.0 and 3.5 mg kg⁻¹, respectively. Repeatability, expressed as relative standard deviation, was 4.6% (n = 9). The method was successfully applied to the determination of free and hydrolyzed formaldehyde in several textile samples, the found results being in good agreement with those obtained with the EN ISO 14184-1:1998 method.     

Investigation on novel thermoplastic poly(urethane-thiourea-imide)s with enhanced chemical and heat resistance

A new generation of segmented thermoplastic poly(urethane-thiourea-imide)s (PUTIs) was synthesized via reaction of polyethylene glycol and thiourea-based prepolymer with dianhydride as chain extenders. NCO-terminated prepolymer was synthesized from a new diisocyanate, 3-(3-((4-isocyanatophenyl)carbamoyl)thioureido)phenyl-4-isocyanatophenylcarbamate (IPCT), as a hard segment and PEG forming soft segment. The starting materials and polymers were characterized by conventional methods and physical properties such as solubility, solution viscosity, molecular weight, thermal stability and thermal behavior were studied. PUTIs showed partially crystalline structures. Weight average molecular weights of PUTIs (GPC measurements) were in the range of 1,68,694-1,97,035. Moreover, thermogravimetric analysis indicated that poly(urethane-thiourea-imide)s were fairly stable above 500 °C having T₁₀ of 521-543 °C. Investigation of the results authenticated the approach of introducing thiourea (using IPCT) and imide structure in polyurethanes for the improvement of thermal stability. In comparison to typical polyurethanes, these polymers exhibited better heat resistance, chemical resistance as well as processability.     

THE INTERACTION OF THE EXCITED STATES OF SAFRANINE T WITH ALIPHATIC AMINES IN ORGANIC SOLVENTS

Abstract—
The reactions of the excited states of safranine T with aliphatic amines have been studied in methanol and acetonitrile. Quenching of the singlet and triplet states occurs by different mechanisms. Whereas the former excited state is quenched by a charge-transfer mechanism, the triplet state is quenched through proton transfer from the excited dye to the amine. This process leads to the unprotonated form of the dye in the triplet state, which is later quenched by amines to form the corresponding semireduced species. The monoprotonated triplet also undergoes self-quenching in both solvents (k = 1.2 × 10⁸ M ^-1 s^-1).     

New use of bis(benzotriazolyl)-1,2-(dialkylamino)ethanes for the synthesis of 2-H-3-dialkylamino imidazo[1,2-a]pyrazine derivatives

First direct synthesis of 2-H-3-N-dialkyl-imidazo[1,2-a]pyrazines is described. This approach makes use of accessible substituted pyrazines and the assistance of benzotriazole. In such a manner we accomplished the introduction of cyclic amines at C-3 of the scaffold in a convenient formal cyclisation procedure. Detailed examples and utility of this approach are presented herein.     

Investigation on the protective effects of cranberry against the DNA damage induced by benzo[a]pyrene

There are few reports that demonstrate the antigenotoxic potential of cranberries. Although the types of berry fruits consumed worldwide are many, this paper focuses on cranberries that are commonly consumed in Mexico (Vaccinium macrocarpon species). The purpose of the present study is to determine whether cranberry ethanolic extract (CEE) can prevent the DNA damage produced by benzo[a]pyrene (B[a]P) using an in vivo mouse peripheral blood micronucleus assay. The experimental groups were organized as follows: a negative control group (without treatment), a positive group treated with B[a]P (200 mg/kg), a group administered with 800 mg/kg of CEE, and three groups treated with B[a]P and CEE (200, 400, and 800 mg/kg) respectively. The CEE and benzo[a]pyrene were administered orally for a week, on a daily basis. During this period the body weight, the feed intake, and the determination of antigenotoxic potential were quantified. At the end of this period, we continued with the same determinations for one week more (recovery period) but anymore administration of the substances. The animals treated with B[a]P showed a weight increase after the first week of administration. The same phenomenon was observed in the lots combined with B[a]P and CEE (low and medium doses). The dose of 800 mg/kg of CEE showed similar values to the control group at the end of the treatment period. In the second part of the assay, when the substances were not administered, these experimental groups regained their normal weight. The dose of CEE (800 mg/kg) was not genotoxic nor cytotoxic. On the contrary, the B[a]P increases the frequency of micronucleated normochromatic erythrocytes (MNNE) and reduces the rate of polychromatic erythrocytes (PE) at the end of the treatment period. With respect to the combined lots, a significant decrease in the MN rate was observed from the sixth to the eighth day of treatment with the two high doses applied; the highest protection (60%) was obtained with 800 mg/kg of CEE. The same dose showed an anticytotoxic effect which corresponded to an improvement of 62.5% in relation to the animals administered with the B[a]P. In the second period, all groups reached values that have been seen in the control group animals. Our results suggest that the inhibition of clastogenicity of the cranberry ethanolic extract against B[a]P is related to the antioxidant capacity of the combination of phytochemicals present in its chemical composition.     

Physicochemical characteristics of protein-NP bioconjugates: the role of particle curvature and solution conditions on human serum albumin conformation and fibrillogenesis inhibition

Gold nanoparticles (Au NPs) from 5 to 100 nm in size synthesized with HAuCl(4) and sodium citrate were complexed with the plasma protein human serum albumin (HSA). Size, surface charge, and surface plasmon bands of the Au NPs are largely modified by the formation of a protein corona via electrostatic interactions and hydrogen bonding as revealed by thermodynamic data. Negative values of the entropy of binding suggested a restriction in the biomolecule mobility upon adsorption. The structure of the adsorbed protein molecules is slightly affected by the interaction with the metal surface, but this effect is enhanced as the NP curvature decreases. Also, it is observed that the protein molecules adsorbed onto the NP surface are more resistant to complete thermal denaturation than free protein ones as deduced from the increases in the melting temperature of the adsorbed protein. Differences in the conformations of the adsorbed protein molecules onto small (<40 nm) and large NPs were observed on the basis of ζ-potential data and FTIR spectroscopy, also suggesting a better resistance of adsorbed protein molecules to thermal denaturing conditions. We think this enhanced protein stability is responsible for a reduced formation of HSA amyloid-like fibrils in the presence of small Au NPs under HSA fibrillation conditions.