A comparison of the effects of prenatal exposure of CD‐1 mice to three imidazolium‐based ionic liquids

BACKGROUND: Ionic liquids (ILs; salts with melting points below 100°C) exhibit wide liquid ranges, non‐flammability, and thermal stability among other properties. These unique salts are best known as “green” alternatives to traditional volatile organic solvents, which are utilized in both academia and industry. Our current study compares the developmental toxicity potential of three representative ionic liquids, with various chain lengths: 1‐ethyl‐3‐methylimidazolium chloride ([C₂mim]Cl), 1‐butyl‐3‐methylimidazolium chloride ([C₄mim]Cl), and 1‐decyl‐3methylimidazolium chloride ([C₁₀mim]Cl). METHODS: From gestation days (GD) 6‐16, mated CD‐1 mice were orally dosed with one of the following: 1,000, 2,000, or 3,000 mg/kg/day [C₂mim]Cl; 113, 169, or 225 mg/kg/day [C₄mim]Cl; 50, 75, or 100 mg/kg/day [C₁₀mim]Cl; or the vehicle only. Dams were sacrificed on GD 17, and their litters were examined for adverse effects. RESULTS: Fetal weight was significantly decreased in the two highest dosage groups exposed to [C₄mim]Cl and [C₁₀mim]Cl in comparison with their controls, but the [C₂mim]Cl treated groups were not affected. An apparent teratogenic effect was associated with both [C₄mim]Cl and [C₁₀mim]Cl, as the offspring exhibited certain uncommon morphological defects. However, the incidences of malformations were low and no correlation between incidence and dosage could be made. No morphological defects were observed in any of the [C₂mim]Cl‐treated groups, despite maternal morbidity at the highest dosage level. CONCLUSIONS: This study indicates that [C₄mim]Cl and [C₁₀mim]Cl may have adverse effects on development at high maternal exposures and strongly supports the supposition that the toxicity of imidazolium‐based ILs is influenced by alkyl chain length. Birth Defects Res (Part B) 89:233–238, 2010. © 2010 Wiley‐Liss, Inc.     

Stabilization of alpha-chymotrypsin by ionic liquids in transesterification reactions.

Five different ionic liquids, based on dialkylimidazolium and quaternary ammonium cations associated with perfluorinated and bis (trifluoromethyl) sulfonyl amide anions, were used as reaction media to synthesize N-acetyl-L-tyrosine propyl ester by transesterification with alpha-chymotrypsin at 2% (v/v) water content at 50 degrees C. The synthetic activity was reduced by the increase in alkyl chains length of cations and by increases in anion size, which was related to the decrease in polarity. Incubation of the enzyme (with and without substrate) in ionic liquids exhibited first-order deactivation kinetics at 50 degrees C, allowing determination of deactivation rate constants and half-life times (1-3 h). Ionic liquids showed a clear relative stabilization effect on the enzyme, which was improved by increased chain length of the alkyl substituents on the imidazolium ring cations and the anion size. This effect was 10-times enhanced by the presence of substrate. For example, 1-butyl-3-methylimidazolium hexafluorophosphate increased the alpha-chymotrypsin half-life by 200 times in the presence of substrate with respect to the 1-propanol medium. These results show that ionic liquids are excellent enzyme-stabilizing agents and reaction media for clean biocatalysis in non-conventional conditions.     

Synthesis,characterization, in vitro SAR and in vivo evaluation of N,N′bisnaphthylmethyl 2-alkyl substituted imidazolium salts against NSCLC

Alkyl- and N,N′-bisnaphthyl-substituted imidazolium salts were tested in vitro for their anti-cancer activity against four non-small cell lung cancer cell lines (NCI–H460, NCI–H1975, HCC827, A549). All compounds had potent anticancer activity with 2 having IC₅₀ values in the nanomolar range for three of the four cell lines, a 17-fold increase in activity against NCI-H1975 cells when compared to cisplatin. Compounds 1–4 also showed high anti-cancer activity against nine NSCLC cell lines in the NCI-60 human tumor cell line screen. In vitro studies performed using the Annexin V and JC-1 assays suggested that NCI-H460 cells treated with 2 undergo an apoptotic cell death pathway and that mitochondria could be the cellular target of 2 with the mechanism of action possibly related to a disruption of the mitochondrial membrane potential. The water solubilities of 1–4 was over 4.4 mg/mL using 2-hydroxypropyl-β-cyclodextrin as a chemical excipient, thereby providing sufficient solubility for systemic administration.     

Synthesis of 3alpha-hydroxy-21-(1'-imidazolyl)-3beta-methoxyl-methyl-5alpha-pregnan-20-one via lithium imidazole with 17alpha-acetylbromopregnanone

The synthesis of biologically active 3alpha-hydroxyl-21-(1'-imidazolyl)-3beta-methoxymethyl-5alpha-pregnan-20-one was accomplished in six steps. The key steps were the improvement of stereoselectivity for acetyl isomers in C-17 and the introduction of imidazole into the core structure by use of lithium imidazole. This latter key step provided the desired product in 82% yield without the formation of 1,3-disubstituted imidazolium salt as impurity, which is generally observed in traditional method.     

A new gold(III)-aminoethyl imidazolium aurate salt: Synthesis, characterization and reactivity

Tetrachloroauric acid HAuCl₄ reacts with the ionic liquid 1-(2-aminoethyl)-3-methylimidazolium nitrate [NH₂(CH₂)₂ImMe]NO₃, (2b) or its dicationic ammonium salt [NH₃(CH₂)₂ImMe][NO₃]₂, (3) in methanolic solutions to give the novel gold(III)-aminoethyl imidazolium aurate salt [Cl₃AuNH₂(CH₂)₂ImMe][AuCl₄] (4). The reaction of 4 with [ⁿBu₄]Cl gives [NH₂(CH₂)₂ImMe][AuCl₄] (2c) whereas with acetone the dicationic, iminium-functionalized, imidazolium aurate salt [Me₂C=N(H)(CH₂)₂ImMe][AuCl₄]₂ (5) has been isolated. The structures in the solid state of 2c, 3, 4, and 5 have been determined by X-ray diffraction. The electrochemical behaviour of 4 has been examined by Cyclic voltammetry in acetonitrile and compared with 2c and KAuCl₄.     

Detection of oxidized and glycated proteins in clinical samples using mass spectrometry — A user's perspective

Background

Proteins in human tissues and body fluids continually undergo spontaneous oxidation and glycation reactions forming low levels of oxidation and glycation adduct residues. Proteolysis of oxidised and glycated proteins releases oxidised and glycated amino acids which, if they cannot be repaired, are excreted in urine.

Scope of Review

In this review we give a brief background to the classification, formation and processing of oxidised and glycated proteins in the clinical setting. We then describe the application of stable isotopic dilution analysis liquid chromatography-tandem mass spectrometry (LC-MS/MS) for measurement of oxidative and glycation damage to proteins in clinical studies, sources of error in pre-analytic processing, corroboration with other techniques – including how this may be improved – and a systems approach to protein damage analysis for improved surety of analyte estimations.

Major conclusions

Stable isotopic dilution analysis LC-MS/MS provides a robust reference method for measurement of protein oxidation and glycation adducts. Optimised pre-analytic processing of samples and LC-MS/MS analysis procedures are required to achieve this.

General significance

Quantitative measurement of protein oxidation and glycation adducts provides information on level of exposure to potentially damaging protein modifications, protein inactivation in ageing and disease, metabolic control, protein turnover, renal function and other aspects of body function. Reliable and clinically assessable analysis is required for translation of measurement to clinical diagnostic use. Stable isotopic dilution analysis LC-MS/MS provides a “gold standard” approach and reference methodology to which other higher throughput methods such as immunoassay and indirect methods are preferably corroborated by researchers and those commercialising diagnostic kits and reagents. This article is part of a Special Issue entitled Current methods to study reactive oxygen species - pros and cons and biophysics of membrane proteins. Guest Editor: Christine Winterbourn.