Identification of oxo,epoxy and somecis-carotenoids in high-performance liquid chromatography

Summary Methods of identification of aldehyde, ketonic, 5,6-epoxy, 5,8-epoxy groups andcis double bonds with highcis-peaks in carotenoids in HPLC have been investigated with selected models and a plant extract.     

Comparative analysis of the full set of methylated β‐cyclodextrins as chiral selectors in capillary electrophoresis

The chiral separation ability of the full library of methylated‐β‐cyclodextrins towards pharmacologically significant racemic drugs including basic compounds was studied by chiral CE. The syntheses of all the methylated, single isomer β‐cyclodextrins were revised and optimized and the aqueous solubility of the derivatives was unambiguously established. The three most relevant commercially available methylated isomeric mixtures were also included in the screening, so a total of ten various methylated CDs were investigated. The effects of the selector concentration on the enantiorecognition properties at acidic pH were investigated. Among the dimethylated β‐cyclodextrins, the heptakis (2,6‐di‐O‐methyl)‐β‐cyclodextrin isomer (2,6‐DIMEB) resulted to be the most versatile chiral selector. Terbutaline was selected as a model compound for the in‐depth investigation of host‐guest enantiodiscrimination ability. The association constants between the two terbutaline enantiomers and 2,6‐DIMEB were determined in order to support that the enantioseparation is driven by differences is host‐guest binding. The migration order of the enantiomers was confirmed by performing spiking experiments with the pure enantiomers. 1D and 2D NMR spectroscopy was applied to the 2,3‐, and 2,6‐DIMEB/terbutaline systems to rationalize at molecular level the different enantioseparation ability of the dimethylated β‐cyclodextrin selectors.     

Contribution of individual flavonoids in Lysimachia species to the antioxidant capacity based on HPLC-DPPH assay

Quantitative phytochemical characterisation of the chief flavonoid aglycones in the hydrolysed Lysimachia extracts revealed the dominance of kaempferol, quercetin and myricetin in L. vulgaris, L. nummularia, L. punctata, L. christinae, L. ciliata and L. clethroides, respectively. Due to the significant radical scavenging capacity of the samples, the contribution of the individual aglycones to the total antioxidant activity became of interest. Therefore, a HPLC method coupled to pre-column DPPH scavenging assay was developed. Differences in the six Lysimachia species’ phenolic composition regarding their participation to the antioxidant activity were revealed. The participation of the three investigated flavonoids to the radical quenching activity was the highest (91.2%) in the L. vulgaris sample, the lowest in L. christinae sample with 29.6%. In L. vulgaris sample, the 76.3% contribution of quercetin to the scavenger capacity was the highest peak area decrement ratio among the investigated samples.     

Complete structural characterization of metallacyclic complexes in solution-phase using simultaneously X-ray diffraction and molecular dynamics simulation

Wide-angle X-ray diffraction and molecular dynamics simulation has been used to perform complete structural characterization of nitromethane solution of a 16-membered gold(I) ring. The joint application of these two methods was an adequate tool to describe not only the structure of the complex but also the solvation properties of the complex in nitromethane and the effect of the solvation on the bulk structure. It has been found that a relatively diffuse slightly distorted solvation shell is formed around the complex, following the shape of the molecule. Nitromethane molecules in the solvation sphere are distributed randomly; no special orientation can be detected. The interaction energy of the complex with nitromethane molecules is attractive. In bulk, besides the antiparallel orientation of the nitromethane molecules, T-shape orientation and long-range order in antidipole orientation can also be detected.     

On a problem of Erdős and Graham

In this paper we provide bounds for the size of the solutions of the Diophantine equation

$$\begin{aligned} x(x+1)(x+2)(x+3)(x+m)(x+m+1)(x+m+2)(x+m+3)=y^2, \end{aligned}$$

where \(4\le m\in \mathbb {N}\) is a parameter. We also determine all integral solutions for \(1\le m\le 10^6.\)

     

Preparation of benzoate esters of morphine and its derivatives

Abstract  

Sustained analgesia is crucial for patients suffering from long-acting pain. Ester derivatives of morphine could enhance the lipophilicity of morphine; consequently its transdermal delivery as well as its duration of action are also increased. Therefore, twenty-one 3-O-, 6-O-, and 14-O-benzoate esters of morphine and their derivatives were synthesized in order to elaborate different synthetic methods suitable for esterification of these widely used compounds. Schotten–Baumann reaction was applied with sodium hydrogen carbonate, triethylamine, or pyridine in methylene chloride or 1,2-dichloroethane as solvents. The presence of 4-dimethylaminopyridine catalyst was also successfully utilized mainly in the case of tertiary alcohols. A novel synthesis of dihydromorphine via diacetyl morphine free of by-products is also presented. Structures of all synthesized compounds were elucidated by ¹H nuclear magnetic resonance (NMR), ¹³C NMR, high-resolution mass spectrometry (HRMS), and electron ionization mass spectrometry (EI-MS). The log D (pH 7.4) values of the synthesized compounds were determined by a reversed-phase high-performance liquid chromatography (HPLC)–MS-based method, and calculated hydrolysis rate constants are also provided. The synthesized benzoate esters are potential prodrugs of the parent morphine with enhanced lipophilicity, derivatives which can also be used in transdermal drug delivery as prospective long-acting narcotic analgesics.     

Axiomatizing complex algebras by games

Given a variety , we provide an axiomatization of the class of complex algebras of algebras in . can be obtained effectively from the axiomatization of ; in fact, if this axiomatization is recursively enumerable, then is recursive. Received January 18, 2000; accepted in final form December 18, 2000.     

Fire Retarded Insulating Sheets from Recycled Materials

In this work we aimed at forming partially recycled polymer composites of appropriate mechanical properties and flame retardancy. Multilayer composite structures proved to be suitable to fulfill all of these requirements. Core-shell structures presented here contain two-component thermosets, i.e. epoxy, recycled polyurethane and polyisocyanurate, as matrices reinforced with waste fillers such as short basalt fibers and wood chips. Flame retardancy and mechanical properties of the core-shell structures were investigated by the conventional methods of characterization. The developed cost-effective multilayer composites can be applied as heat and sound insulating panels e.g. multifunctional sheets for construction or automotive industry.