Analysis of diethylstilbestrol and its impurities in tablets using reversed-phase high-performance liquid chromatography

A high-performance liquid chromatographic (HPLC) method is described which is capable of resolving cis- and trans-diethylstilbestrol (DES), DES mono- and dimethyl ethers and 4,4'-dihydroxystilbene. The mobile phase and internal standard used stabilise the cis-trans DES isomer ratio, and the method is capable of quantitating both isomers in dosage forms without derivatisation. Recovery of DES from tablets is quantitative. Results of tablet analyses using this method are compared with those obtained with the official spectrophotometric procedure.     

Electron Transfer and Collision Induced Dissociation of Non-Derivatized and Derivatized Desmosine and Isodesmosine

Electron transfer dissociation (ETD) has attracted increasing interest due to its complementarity to collision-induced dissociation (CID). ETD allows the direct localization of labile post-translational modifications, which is of main interest in proteomics where differences and similarities between ETD and CID have been widely studied. However, due to the fact that ETD requires precursor ions to carry at least two charges, little is known about differences in ETD and CID of small molecules such as metabolites. In this work, ETD and CID of desmosine (DES) and isodesmosine (IDS), two isomers that due to the presence of a pyridinium group can carry two charges after protonation, are studied and compared. In addition, the influence of DES/IDS derivatization with propionic anhydride and polyethyleneglycol (PEG) reagents on ETD and CID was studied, since this is a common strategy to increase sensitivity and to facilitate the analysis by reversed-phase chromatography. Clear differences between ETD and CID of non-derivatized and derivatized-DES/IDS were observed. While CID is mainly attributable to charge-directed fragmentation, ETD is initiated by the generation of a hydrogen atom at the initial protonation site and its subsequent transfer to the pyridinium ring of DES/IDS. These differences are reflected in the generation of complex CID spectra dominated by the loss of small, noninformative molecules (NH₃, CO, H₂O), while ETD spectra are simpler and dominated by characteristic side-chain losses. This constitutes a potential advantage of ETD in comparison to CID when employed for the targeted analysis of DES/IDS in biological samples.

Desferrioxamine dehydrogenates bilirubin in two stages,leading to a 1:1 red‐coloured adduct. Characterization of the products by high‐performance liquid chromatography/electrospray ionization mass spectrometry

We have used open‐chain tetrapyrroles, such as bilirubin, as molecular probes to investigate the pro‐oxidant activity of desferrioxamine (DES) and its modulation by Trolox. On exposure to Fe‐EDTA/H₂O₂, bilirubin and mesobilirubin underwent bleaching. When DES was present, bleaching was prevented and both rubins were converted into green‐coloured derivatives and then into red pigments. Trolox added with DES inhibited the colour changes induced by DES. The oxidative products were resolved from their parent compounds by high‐performance liquid chromatography (HPLC) and studied by electrospray ionization mass spectrometry and by UV/visible spectroscopy. The green products were identified as biliverdin or mesobiliverdin; the red pigments as the 1:1 molar adduct of DES with biliverdin or mesobiliverdin, less two hydrogens in both cases. It is concluded that DES exercises its oxidative activity through nitroxyl oxidizing radicals capable of efficient hydrogen abstraction, dehydrogenating either rubin to the corresponding verdin. A diradical derivative of DES (bearing two nitroxyl radicals in the same molecule) may be involved in the oxidation of verdins to red pigments, through concerted dehydrogenation and adduct formation. These results shed further light on the redox properties of bilirubin, DES and Trolox, and their interactions. They provide further evidence of the pro‐oxidant activity of DES and suggest a more general biological significance, as rapid removal of bilirubin by bleaching or dehydrogenation may have pharmacological/toxicological implications in severe jaundice. Copyright © 2008 John Wiley & Sons, Ltd.     

Voltammetric determination of diethylstilbestrol at carbon paste electrode using cetylpyridine bromide as medium

In this paper, the voltammetric properties of diethylstilbestrol (DES) at the carbon paste electrode were described. The oxidation peak currents of DES increase significantly in the presence of surfactant cetylpyridine bromide (CPB), compared with that in the absence of CPB. Based on this fact, a voltammetric technique for determining DES is proposed. The accumulation potential has no effects on the peak current of the DES. An open-circuit accumulation is carried out. The experimental parameters, such as pH value of buffer, scan rate, and accumulation time were optimized. The interferences of some metal ions and organic compounds have also been studied, and some metal ions almost do not interfere with the determination of DES. Using this voltammetric method, DES in the injection sample was measured. The results show that this voltammetric method is reliable for the practice determination of DES.     

低共熔溶剂用于高效可逆捕集二氧化碳的研究

本文通过一步合成法合成了四种不同摩尔比的四乙基氯化胺-乙醇胺低共熔溶剂（TEAC-MEA DES）。红外光谱表征分析表明该DES是依靠氢键作用而形成的;DES的热稳定性高于MEA,且随着MEA的比例的增加而降低;对不同比例的DES进行了四次循环CO₂吸收-解吸实验,发现其吸收容量几乎不变,重复使用性能较好。在不同温度下计算了化学平衡常数,lnK对1/T线性拟合结果表明DES吸收CO₂的反应焓是负值,即吸收CO₂的反应是放热过程。该DES在吸收CO₂方面具有很大的潜力。     

Cellulose nanocrystals from bleached rice straw pulp: acidic deep eutectic solvent versus sulphuric acid hydrolyses

The present work aims to investigate the feasibility of oxalic acid-choline chloride deep eutectic solvent (OA-ChCl DES), which serves as a promising green solvent that utilized in the acidic deep eutectic solvent (DES) hydrolysis. Oxalic acid-choline chloride DES cellulose nanocrystal (OA-ChCl DES CNC) was isolated from the bleached DES treated pulp (BP) through the acidic DES hydrolysis using 1:1 molar ratio of OA-ChCl DES. The functional groups, crystallinity index, morphological structure, particle size, zeta potential, thermal stability and surface chemistry of the OA-ChCl DES CNC were compared with the sulphuric acid cellulose nanocrystal (SA-CNC) that prepared via sulphuric acid hydrolysis. The findings revealed the presence of negatively charged carboxyl groups on OA-ChCl DES CNC surface after the acidic DES hydrolysis. The physicochemical analyses verified that the OA-ChCl DES CNC was in nano-sized range with polydispersity index (PdI) of 0.56, indicating slightly monodispersed nanoparticles. A stable OA-ChCl DES CNC colloidal suspension with zeta potential value of ?52.1?±?5.2 mV was obtained. The OA-ChCl DES CNC outweighed the SA-CNC in term of thermal stability (288 °C) despite having a slightly lower crystallinity index (76.7%). In fact, the OA-ChCl DES CNC with a yield of 55.1% was achieved through the acidic DES hydrolysis, suggesting that the OA-ChCl DES was capable of promoting efficient cleavage of strong hydrogen bonds in BP.

Graphic abstract

     

COSMOtherm as an Effective Tool for Selection of Deep Eutectic Solvents Based Ready-To-Use Extracts from Graševina Grape Pomace

The aim of this work is to develop an industrially suitable process for the sustainable waste disposal in wine production. The proposed process involves the development of an environmentally friendly method for the isolation of biologically active compounds from Graševina grape pomace according to the green extraction principles, in order to obtain a ready-to-use extract. In this process, deep eutectic solvents (DES) were used as extraction solvents. Aiming to save time in selecting the optimal DES that would provide the most efficient Graševina pomace polyphenols extraction, the user-friendly software COSMOtherm was used and 45 DES were screened. Moreover, the prepared extracts were chemically and biologically characterized to confirm their safety for human application. Computational and experimental results proved the applicability of COSMOtherm in the selection of the optimal DES for the environmentally friendly preparation of the ready-to-use extract from Graševina grape pomace with expected application in the cosmetic industry.     

Liquefying Flavonoids with Terpenoids through Deep Eutectic Solvent Formation

The formation of deep eutectic solvents (DES) is tied to negative deviations to ideality caused by the establishment of stronger interactions in the mixture than in the pure DES precursors. This work tested thymol and menthol as hydrogen bond donors when combined with different flavonoids. Negative deviations from ideality were observed upon mixing thymol with either flavone or flavanone, two parent flavonoids that only have hydrogen bond acceptor (HBA) groups, thus forming non-ionic DES (Type V). On the other hand, the menthol systems with the same compounds generally showed positive deviations from ideality. That was also the case with the mixtures containing the more complex hydroxylated flavonoid, hesperetin, which resulted in positive deviations when mixed with either thymol or menthol. COSMO-RS successfully predicted the behavior of the solid-liquid phase diagram of the studied systems, allowing for evaluation of the impact of the different contributions to the intermolecular interactions, and proving to be a good tool for the design of DES.     

Applications of Deep Eutectic Solvents in Sample Preparation and Extraction of Organic Molecules

The use of deep eutectic solvents (DES) is on the rise worldwide because of the astounding properties they offer, such as simplicity of synthesis and utilization, low-cost, and environmental friendliness, which can, without a doubt, replace conventional solvents used in heaps. In this review, the focus will be on the usage of DES in extracting a substantial variety of organic compounds from different sample matrices, which not only exhibit great results but surpass the analytical performance of conventional solvents. Moreover, the properties of the most commonly used DES will be summarized.     

A new molecularly imprinted polymer for the on-column solid-phase extraction of diethylstilbestrol from aqueous samples

The estrogenic compound diethylstilbestrol (DES) is widely studied because of its potential endocrine disruption effects. The prohibition of the use of diethylstilbestrol as a growth promoter has not been enough to ensure the total disappearance of this compound from environmental matrices. Due to the low levels of DES present in the environment, preconcentration and clean up methods are necessary for its analysis. This paper describes the synthesis and use of a molecularly imprinted polymer (MIP) as sorbent for on-column solid-phase extraction of DES from aqueous samples. The selectivity of the DES-MIP was evaluated towards several selected estrogens such as hexestrol (HEX), estrone (E1), estriol (E3), estradiol (E2) and ethynylestradiol (EE2). HPLC-DAD was used to quantify all analytes at 230-nm wavelength. The method has been successfully applied to the analysis of DES in spiked river and tap water samples, with recoveries of 72% and 83% respectively.     

深共熔溶剂在有机反应中的应用

深共熔溶剂(DES)作为一种低共熔混合物,由于具有廉价易得、蒸汽压低、无毒性、不易燃、可生物降解、可调控以及易循环使用等优点,逐渐成为一种新型的绿色溶剂或催化剂。本文介绍了DES的组成、分类,重点综述了DES作为溶剂或催化剂应用于常见的加成、取代、偶联、缩合、环化、酯化、多组分及解聚等有机反应。最后展望了DES在有机反应中的发展前景。     

The Effect of Water upon Deep Eutectic Solvent Nanostructure: An Unusual Transition from Ionic Mixture to Aqueous Solution

The nanostructure of a series of choline chloride/urea/water deep eutectic solvent mixtures was characterized across a wide hydration range by neutron total scattering and empirical potential structure refinement (EPSR). As the structure is significantly altered, even at low hydration levels, reporting the DES water content is important. However, the DES nanostructure is retained to a remarkably high level of water (ca. 42 wt % H₂O) because of solvophobic sequestration of water into nanostructured domains around cholinium cations. At 51 wt %/83 mol % H₂O, this segregation becomes unfavorable, and the DES structure is disrupted; instead, water–water and DES–water interactions dominate. At and above this hydration level, the DES–water mixture is best described as an aqueous solution of DES components.     

Coherent Exciton-Phonon Coupling in CdSe/ZnS Nanocrystals Studied by Two-Dimensional Electronic Spectroscopy

Coherent exciton-phonon coupling in CdSe/ZnS nanocrystals have been investigated by temperature-dependent two-dimensional electronic spectroscopy (2DES) measurements. Benefiting from the ability of 2DES to dissect assembles in nanocrystal films, we have clearly identified experimental evidences of coherent coupling between exciton and phonon in CdSe/ZnS nanocrystals. In time domain, 2DES signals of excitonic transitions beat at a frequency resonant to a longitudinal optical phonon mode; in energy domain, phonon side bands are distinct at both Stokes and anti-Stokes sides. When temperature increases, phonon-induced exciton dephasing is observed with dramatic broadening of homogeneous linewidth. The results suggest exciton-phonon coupling is essential in elucidating the quantum dynamics of excitonic transitions in semiconductor nanocrystals.     

Studies on steroids. CCLIII. Capillary gas chromatographic behaviour of diethylhydrogensilyl-diethylsilylene derivatives of stereoisomeric bile acids.

The capillary gas chromatographic behaviour of diethylhydrogensilyl (DEHS) ethers and/or diethylsilylene (DES) derivatives of fifty bile acids including 4- and 6-hydroxylated compounds is described. The methylene unit (MU) values of methyl and pentafluorobenzyl esters of bile acids were determined as their trimethylsilyl (TMS), dimethylethylsilyl (DMES) ethers and DEHS-DES derivatives. The differences in methylene unit values between the corresponding TMS ethers and DMES ethers or DEHS-DES derivatives were used for estimating the number and stereochemistry of hydroxyl groups on the steroid nucleus. On treatment with the silylating agent N,O-bis (diethylhydrogensilyl)trifluoroacetamide, bile acids possessing isolated hydroxyl in addition to diaxial trans-glycol groups were easily converted into the DEHS ehters, whereas those having a vicinal glycol group except for the diaxial group were converted into cyclic DES derivatives. The mass spectrometric properties obtained with negative-ion chemical ionization detection are discussed.     

Comparison of enzyme-linked immunosorbent assay with liquid chromatography-tandem mass spectrometry for the determination of diethylstilbesterol residues in chicken and liver tissues

A competitive enzyme-linked immunosorbent assay (ELISA) was developed for the quantitative detection of the diethylstilbesterol (DES). Polyclonal rabbit antisera, raised against protein conjugate diethylstilbesterol-mono-caroxyl-propyl-ethyl-bovine-serum-albumin (DES-MCPE-BSA), were utilized in immobilized antibody-based and competitive immunoassays. Assay conditions, including concentrations of antisera and horseradish peroxidase, (HRP)-DES, were optimized. The effects of incubation time, surfactant concentration, ionic strength and pH of the medium were also investigated. The typical calibration curve gave an average IC(50) value of 2.4 ng/mL, calibration range from 0.2 to 30.5 ng/mL and a detection limit of 0.07 ng/mL. The specificity of the assay was tested against DES structurally related compounds, and the assay proved highly selective for DES. Assay performance was validated using spiked chicken meat and liver tissue samples. Moreover, it was compared with liquid chromatography-tandem mass spectrometry. The ion pair for quantification of DES was m/z 267.4/251.4, and the linear equation of DES was y = 0.1033x + 0.0126 (r = 0.9960). The two analytical methods can be applied to monitor DES and other steroid residues in foods.     

Penetration Process of a Hydrated Deep Eutectic Solvent Through the Stratum Corneum and its Application as a Protein Penetration Enhancer

The penetration mechanism of choline chloride-glycerol deep eutectic solvent (DES) through the stratum corneum (SC) as a potential solvent for a novel enhancer of protein penetration into the skin was investigated in a wide and small angle X-ray diffraction study. We found that DES penetrated through intercellular lipids but not the corneocytes. DES seemed to extract a portion of lipids of the short lamellae in the SC. Hydrated DES with a DES to water weight ratio of 9 to 1 (9DES-1H₂O) showed the strongest interaction with the lipids in the SC compared with water, DES, and hydrated DESs with another weight ratio of DES to water (DES : water=8 : 2). In a skin penetration test with a fluorescently labelled lysozyme, 9DES-1H₂O increased the amount of penetration through the SC by two-fold compared with HEPES buffer.     

Incubation-free electrochemical immunoassay for diethylstilbestrol in milk using gold nanoparticle-antibody conjugates for signal amplification

We report on a novel enzyme-enhanced label for the electrochemical determination of diethylstilbestrol (DES). The label was obtained by orientation-controlled immobilization of a multiplex horseradisch peroxidase (HRP) conjugated polymer on gold nanoparticles (AuNPs) using the Envision reagent (EV) which is an enzyme-polymer complex that contains HRP and anti-IgG antibody in a polydextrin amine skeleton. The AuNPs were modified with Concanavalin A (Con A) and served as a carrier for immobilization of the EV?DES antibody composite. This resulted in a bioconjugate of the type AuNP?Con A?EV?DES Ab which was employed as the label. On exposure to samples containing DES, a sandwich immunocomplex is formed between antibody against DES (which was immobilized on a glassy carbon electrode and is acting as a capture probe), DES (the analyte), and the above label as the signal tracer. Hemin was used as an electronic mediator in the reaction of HRP. The HRP on the label catalyzes the oxidative formation of hydrogen peroxide at pH 7.0, and this induces an increased reductive current in the presence of hemin as an electron mediator. Under optimal conditions, the current increases linearly with increasing concentrations of DES in the range from 5 to 500 pg?·?mL^?1, with a detection limit as low as 2 pg?·?mL^?1 (at an S/N of 3). The method exhibits high selectivity and good stability. It works without incubation so that the time for an assay is shortened to 5 min. The assays was successfully applied to the determination of DES in milk samples.

Comparison of conventional immunoassays and the oestrogen radioreceptor assay for screening for the presence of oestrogenic anabolic compounds in urine samples.

Screening for the presence of anabolic growth promoters in urine samples from cattle grown for meat production can be performed by (semi)quantitative methods such as immuno-, receptor- or cell-based assays or by quantitative methods with mass spectrometric detection which can also include confirmation of compounds. In this study conventional immunoassays used at two different institutes [Veterinary Sciences Division (VSD) in Northern Ireland and TNO Nutrition and Food Research Institute (TNO) in The Netherlands] were compared with the oestrogen radioreceptor assay (ORRA), with GC-MS as the reference method. Urine samples were generated by treating calves (n = 2 per group) intramuscularly with ethynyloestradiol (EE2), diethylstilbestrol (DES) or alpha-zearalanol (zeranol, ZER). Urine samples were collected up to 21 d after administration of the oestrogenic compounds. Samples were screened by enzyme immunoassay or radioimmunoassay and by the ORRA and also by GC-MS. Values found by VSD were lower by a factor of 1-20 than those measured by TNO. These differences could be explained by differences in sample clean-up (immunoaffinity chromatography versus solid-phase extraction) and by differences in cross-reactivities between the antisera used. The ORRA and GC-MS showed similar results for EE2 and DES, but produced lower results (by a factor of ca. 3) for ZER owing to the relatively low affinity of ZER for the oestrogen receptor. The most important finding was that the withdrawal period for calves treated with EE2, DES or ZER was similar for each of the screening methods used. Therefore, it is concluded that the choice of screening method does not affect the probability of finding a positive sample.     

Chiral Deep Eutectic Solvents Enable Full-Color and White Circularly Polarized Luminescence from Achiral Luminophores

Herein, chiral deep eutectic solvents (DES) are prepared by lauric acid as hydrogen bond donors (HBD) and chiral menthol as hydrogen bond acceptors (HBA). When achiral fluorescent molecules are dopedin the menthol-based chiral DES, they emit circularly polarized luminescence (CPL) with handedness controlled by the molecular chirality (l or d ) of menthol. Remarkably, the strategy is universal and a series of achiral fluorescent molecules can be endowed with CPL activity, showing a full-color and white CPL upon appropriate mixing, which paves the way to prepare white CPL materials. Interestingly, CPL appears only in a certain temperature range in the DES. Variable-temperature spectra and other characterization methods reveal that the H-bond network in the chiral DES plays an important role in inducing CPL. This work unveils how the interior structure as well as the hydrogen-bond network of a chiral DES can transfer its chirality to achiral luminophores for the first time and realizes a full-color and white CPL in a DES.     

Are deep eutectic solvents a real alternative to ionic liquids in metal-catalysed reactions?

This microreview tries to answer the question: Are Deep Eutectic Solvents a real alternative to Ionic Liquids in metal-catalysed reactions? We have gathered the outstanding results of the use of DES in metal-catalysed processes and we have compared them to the ones with ILs. The huge possibilities of combinations of the components of the DES provide a vast number of different solvents with tunable properties. These DES have been successfully applied to different reactions such as, couplings or hydrogenations, among others. But additional work is still be necessary to explore the use of DES in other reactions and to go in depth in the study of the influence of the nature of the DES. Finally, we also present the rise in a new family of solvents, bio-based ionic liquids, complementary to the use of DES in order to fully substitute traditional ILs.