Intramolecular ketenimine-ketenimine [2 + 2] and [4 + 2] cycloadditions

Bis(ketenimines), in which the two heterocumulenic functions are placed in close proximity on a carbon skeleton to allow their mutual interaction, show a rich and not easily predictable chemistry. Intramolecular [2 + 2] or [4 + 2] cycloadditions are, respectively, observed when both ketenimine functions are supported on either ortho-benzylic or 2,2'-biphenylenic scaffolds. In addition, nitrogen-to-carbon [1,3] and [1,5] shifts of arylmethyl groups in N-arylmethyl-C,C-diphenyl ketenimines are also disclosed.     

Effective methods for the biotinylation of azamacrocycles

The biotin-(strept)avidin interaction remains a gold standard of model biological recognition events. The biotinylation of azamacrocycles permits the investigation of signal transduction between this recognition event and the metal center of an azamacrocycle complex, of wide potential interest in biosensing. There are no generally applicable procedures in the literature for such functionalizations. We report here a comprehensive investigation into the attachment of biotin to TACN, cyclen, and cyclam. Effective methods have been found for each ring. The efficacy of the functionalization is critically dependent on the nature of the azamacrocycle.     

Fast determination of herbicides in waters by ultra-performance liquid chromatography/tandem mass spectrometry

A rapid multiresidue method for the analysis of more than 40 herbicides (such as simazine, terbuthylazine and diuron) in waters has been developed and validated by ultra-performance liquid chromatography coupled to tandem mass spectrometry (UPLC/MS/MS). Prior to chromatographic determination, the samples were extracted using a solid-phase extraction procedure. The analysis was performed on an Acquity UPLC BEH C(18) column using a gradient elution profile and a mobile phase consisting of methanol and an aqueous solution of formic acid (0.01%). Other chromatographic and MS/MS parameters were optimised in order to improve selectivity and sensitivity of the analytes. The analytes were detected using electrospray ionisation (ESI)-MS/MS in positive ion mode with multiple reaction monitoring (MRM), optimising parameters such as voltage cone, capillary voltage, source and desolvation temperature, and desolvation and cone gas flow. The optimised method provides a rapid separation (less than 10 min) of the selected herbicides in the assayed matrices, and it was validated by the analysis of spiked blank matrix samples. Good linearity was obtained and the repeatability of the method was less than 20% for the lowest calibration point. The limits of detection ranged from 0.002 to 0.02 microg/L, and the limits of quantification from 0.005 to 0.05 microg/L, which were below the values specified by the European Union. Finally, the method was successfully applied to real environmental samples from Andalusia (southern Spain). Terbuthylazine, simazine, atrazine desisopropyl and desethyl terbuthylazine were the herbicides most frequently found in water samples.     

Products of the gas-phase reactions of OH radicals with (C2H5O)2P(S)CH3 and (C2H5O)3PS

Products of the gas-phase reactions of OH radicals with O,O-diethyl methylphosphonothioate [(C2H5O)2P(S)CH3, DEMPT] and O,O,O-triethyl phosphorothioate [(C2H5O)3PS, TEPT] have been investigated at room temperature and atmospheric pressure of air using in situ atmospheric pressure ionization mass spectrometry (API-MS) and, for the TEPT reaction, gas chromatography and in situ Fourier transform infrared (FT-IR) spectroscopy. Combined with products quantified previously by gas chromatography, the products observed were: from the DEMPT reaction, (C2H5O)2P(O)CH3 (21+/-4% yield) and C2H5OP(S)(CH3)OH or C2H5OP(O)(CH3)SH (presumed to be C2H5OP(O)(CH3)SH by analogy with the TEPT reaction); and from the TEPT reaction, (C2H5O)3PO (54-62% yield), SO2 (67+/-10% yield), CH3CHO (22-40% yield) and, tentatively, (C2H5O)2P(O)SH. The FT-IR analyses showed that the formation yields of HCHO, CO, CO2, peroxyacetyl nitrate [CH3C(O)OONO2], organic nitrates, and acetates from the TEPT reaction were <5%, 3+/-1%, <7%, <2%, 5+/-3%, and 3+/-2%, respectively. Possible reaction mechanisms are discussed.     

Theoretical study of new LmDHODH and LmTXNPx complexes: structure-based relationships

Structural Chemistry - In this work, a series of eight novel ring-substituted styrylquinolines were synthesized, and in silico physicochemical properties were estimated. The inhibitory activity of...     

Measurement of the thermal conductivity of MWCNT-CuO/water hybrid nanofluid using artificial neural networks (ANNs)

Journal of Thermal Analysis and Calorimetry - In this paper, artificial neural networks (ANNs) are developed to predict the thermal conductivity ( $$k_{\text{nf}}$$ ) of multi-walled carbon...     

Hovenia dulcis Thumberg: Phytochemistry,Pharmacology, Toxicology and Regulatory Framework for Its Use in the European Union

Hovenia dulcis Thunberg is an herbal plant, belonging to the Rhamnaceae family, widespread in west Asia, USA, Australia and New Zealand, but still almost unknown in Western countries. H. dulcis has been described to possess several pharmacological properties, such as antidiabetic, anticancer, antioxidant, anti-inflammatory and hepatoprotective, especially in the hangover treatment, validating its use as an herbal remedy in the Chinese Traditional Medicine. These biological properties are related to a variety of secondary metabolites synthesized by the different plant parts. Root, bark and leaves are rich of dammarane-type triterpene saponins; dihydrokaempferol, quercetin, 3,3′,5′,5,7-pentahydroflavone and dihydromyricetin are flavonoids isolated from the seeds; fruits contain mainly dihydroflavonols, such as dihydromyricetin (or ampelopsin) and hovenodulinol, and flavonols such as myricetin and gallocatechin; alkaloids were found in root, barks (frangulanin) and seeds (perlolyrin), and organic acids (vanillic and ferulic) in hot water extract from seeds. Finally, peduncles have plenty of polysaccharides which justify the use as a food supplement. The aim of this work is to review the whole scientific production, with special focus on the last decade, in order to update phytochemistry, biological activities, nutritional properties, toxicological aspect and regulatory classification of H. dulcis extracts for its use in the European Union.     

Processing Effect and Characterization of Olive Oils from Spanish Wild Olive Trees (Olea europaea var. sylvestris)

Wild olive trees have important potential, but, to date, the oil from wild olives has not been studied significantly, especially from an analytical point of view. In Spain, the wild olive tree is called “Acebuche” and its fruit “Acebuchina”. The objective of this work is to optimize the olive oil production process from the Acebuchina cultivar and characterize the oil, which could be marketed as healthy and functional food. A Box–Behnken experimental design with five central points was used, along with the Response Surface Methodology to obtain a mathematical experimental model. The oils from the Acebuchina cultivar meet the requirements for human consumption and have a good balance of fatty acids. In addition, the oils are rich in antioxidants and volatile compounds. The highest extraction yield, 12.0 g oil/100 g paste, was obtained at 90.0 min and the highest yield of phenolic compounds, 870.0 mg/kg, was achieved at 40.0 °C, and 90.0 min; but the maximum content of volatile compounds, 26.9 mg/kg, was obtained at 20 °C and 30.0 min. The oil yield is lower than that of commercial cultivars, but the contents of volatile and phenolic compounds is higher.     

Phytochemical Characterization and Bioactivity of Asparagus acutifolius: A Focus on Antioxidant,Cytotoxic, Lipase Inhibitory and Antimicrobial Activities

The phytochemical composition of leaves, stems, pericarps and rhizomes ethanolic extracts of Asparagus acutifolius were characterized by HPLC-DAD-MS. A. acutifolius samples contain at least eleven simple phenolics, one flavonon, two flavonols and six steroidal saponins. The stem extracts showed the highest total phenolic acid and flavonoid contents, where cafeic acid and rutin were the main compounds. No flavonoids were detected in the leaf, pericarp or rhizome while caffeic acid and ferulic acid were the predominant. Steroidal saponins were detected in the different plant parts of A. acutifolius, and the highest contents were found in the rhizome extracts. The stem extracts exhibited the highest antioxidant activity against 2,2-diphenyl-1-picrylhydrazyl (DPPH) and ferric reducing antioxidant power (FRAP) and the highest 2,2-azino-bis (3 ethylbenzothiazoline-6-sulphonic acid) (ABTS) scavenging activity was found in the pericarp extracts. The rhizome and leaf extracts showed a potent cytotoxic activity against HCT-116 and HepG2 cell lines. Moreover, the pericarp and rhizome extracts revealed a moderate lipase inhibitory activity. The leaf and rhizome extracts were screened for their antimicrobial activity against human pathogenic isolates. The leaf extract exhibited a powerful inhibitory activity against all the bacteria and fungi tested.     

A comparison of condensate mass of QCD vacuum between Wilson line approach and Schwinger effect

We studied the condensate mass of QCD vacuum through the duality approach via dilaton wall back-ground in the presence of the parameter c,which represents the condensation in a holographic set up.First,fromWilson line calculation,we found m₀²(i.e.,the condensate parameter in mixed non-local condensation),whose beha-vior mimics that of QCD.The value of m₀²that we found by this approach is in agreement with QCD data.Second we considered the produced mass m via the Schwinger effect mechanism in the presence of the parameter c.We show that vacuum condensation generally contributes the mass dominantly and that the produced mass via Schwing.er effect is suppressed by m₀.