Emilia Tojo

Cytotoxicity of selected imidazolium-derived ionic liquids in the human Caco-2 cell line. Sub-structural toxicological interpretation through a QSAR study

Room-temperature ionic liquids (ILs) are considered green chemicals that may replace volatile organic solvents currently used by industry. However, toxicological effects of ILs are not well known. In this study, we describe the cytotoxicity of selected imidazolium-derived ILs in Caco-2 cells, prototypical human epithelial cells. The most toxic IL was 1-decyl-3-methylimidazolium chloride ([C10mim][Cl]), whereas the least toxic was 1,3-dimethylimidazolium methyl sulfate ([C1mim][MSO4]). Using the toxicological experimental data obtained we developed a Quantitative Structure–Activity Relationship (QSAR) study using the Topological Sub-Structural Molecular Design (TOPS-MODE) approach. The model found showed excellent statistical parameters and from their interpretation, we arrived to some important conclusions such as: For 1-alkyl-3-methylimidazolium chloride derivatives, a correlation between the R2 alkyl chain length and toxicity was observable. A positive contribution of p-chloro substituent in benzyl ring is detected among 1-methylarylimidazolium chloride derivatives. Regarding the contribution of the anion, anion chloride presents a positive contribution to toxicity whereas for compounds [C1mim][MSO4] and [C1eim][ESO4], a negative fragment contribution can be detected in anion methyl or ethyl sulfate. The EC50 values determined for the ILs analysed in this study in Caco-2 cells are lower than the data reported in the literature on the toxicity of classical solvents assessed with cell lines. In conclusion, our results indicate that the possible cytotoxic effect of ILs should be considered in the design and overall evaluation of these compounds. Nevertheless, any toxicity evaluation of ILs should take their bioavailability into account, which will be affected by their low volatility, compared to conventional solvents.

Quantitation of κ-, ι- and λ-carrageenans by mid-infrared spectroscopy and PLS regression

Abstract Carrageenans are natural products obtained from seaweeds which are used as additives in many industrial fields, mainly in the food industry (labelled as E407). The three most employed ones being the so-called κ-, ι- and λ-carrageenans. So far, their industrial characterisation is based on physical measurements, which exhibit a rather large uncertainty. The aim of this work is to develop a new analytical methodology for the quantitative determination of carrageenans in industrial mixtures employing FTIR and multivariate regression (partial least squares, PLS), avoiding complex sample pre-treatment steps and reducing the turnaround time. The methodology allows to handle liquid (dissolved) carrageenans at room temperature (to prevent degradation), and therefore, their straightforward IR measurement using thin films. The standard prediction errors for the different models selected range from 3.3 to 4.2%, which can be considered as excellent.

HMImPF6 ionic liquid that separates the azeotropic mixture ethanol + heptane

1-Hexyl-3-methylimidazolium hexafluorophosphate (HMImPF6) is suitable for use as the solvent in the petrochemical extraction process for the removal of heptane from its azeotropic mixture with ethanol. The experimental determination of the liquid–liquid equilibrium (LLE) for the ternary system heptane + ethanol + HMImPF6 at 298.15 K was carried out. The solute distribution ratio and the selectivity of the HMImPF6 have been determined from the tie-line data. A comparative study has been made in terms of selectivity and solute distribution data with other ionic liquids. The NRTL equation was verified to accurately correlate the experimental data.

Antimicrobial study of the resinous exudate and of diterpenoids isolated from Eupatorium salvia (Asteraceae).

The antimicrobial properties of the resinous exudate from twigs and leaves of Eupatorium salvia were tested against five gram-negative and five gram-positive bacteria. Comparison of the antimicrobial activities of 7-hydroxy-8(17)-labden-15-oic acid (salvic acid) and of its acetate, both compounds isolated from the plant, with that of the crude extract suggested that the latter ester derivative was the major active component in the exudate. These results validate the vernacular medicinal use of Eupatorium salvia as an antiseptic agent.

A simple 1H NMR method for the quantification of carrageenans in blends

Abstract Traditional methods for the structural analysis of carrageenans require hydrolysis and derivation procedures followed by chromatographic analysis of the formed derivatives. These assays are time-consuming and do not adequately quantify the different components in blend samples. This paper describes a simple method for the quantitative determination of kappa, iota and lambda carrageenan in standard mixtures of samples and production batches on intact polymeric carrageenans using 1H NMR spectroscopy.

Synthesis and characterization of new polysubstituted pyridinium-based ionic liquids: application as solvents on desulfurization of fuel oils

The production of transportation fuels which have a very low content of sulfur has became one of the priority challenges for the oil industry worldwide, due to by strict new regulatory requirements. Ionic liquids (ILs) have been proposed as suitable and promising solvents for this purpose due to their excellent qualities as solvents. In this work a series of ten new ILs derived from pyridinium cation substituted with different alkyl chains have been synthesized from 2-alkyl-3,5-dimethylpyridines. The starting materials were prepared by selective metalation of 2,3,5-trimethylpyridine, which allowed the introduction of different alkyl groups in pyridine position 2 with high yields. To test the ILs sulfur-removal capacity, liquid–liquid equilibrium (LLE) data for ternary systems (heptane + thiophene + IL) were determined at T = 298.15 K and atmospheric pressure. Selectivity and solute distribution ratio, calculated from tie-lines, were used to evaluate whether these new ILs could be used as solvents for the extraction of thiophene from heptane. Finally, the experimental LLE data were correlated with the NRLT thermodynamic model.

Knoevenagel Reaction in [MMIm][MSO4]: Synthesis of Coumarins

The ionic liquid 1,3-dimethylimidazolium methyl sulfate, [MMIm][MSO4], together with a small amount of water (the amount taken up by the ionic liquid upon exposure to air), acts efficiently as both solvent and catalyst of the Knoevenagel condensation reactions of malononitrile with 4-substituted benzaldehydes, without the need for any other solvent or promoter, affording yields of 92%–99% within 2–7 min at room temperature. When L-proline is used as an additional promoter to obtain coumarins from o-hydroxybenzaldehydes, the reaction also proceeds in high yields. Work-up is very simple and the ionic liquid can be reused several times. Some of the coumarins obtained are described for the first time.

Pyrrolidinium sulfate and ammonium sulfate ionic liquids as lubricant additives for steel/steel contact lubrication

In this work, we report on the BuMepyr-MeSO4 and Et3MeN-MeSO4 ionic liquids that were synthesized and used as additives in a glycerol model lubricant for steel/steel contacts. Tests were performed with three different ionic liquid concentrations, i.e. 0.625 wt%, 2.5 wt% and 8 wt%, as well as in glycerol without any ionic liquid (neat glycerol) and in neat ionic liquids (100%) at 100 °C. The wear and friction were measured and the worn surfaces were examined with scanning electron microscopy and atomic force microscopy. The results show a reduction of the wear and friction with the use of ionic liquids as additives, when compared to the neat glycerol. With an increasing ionic-liquid concentration in the glycerol, the friction was observed to decrease and the wear to increase. In this work, however, the results obtained for neat ionic liquids represent the lowest values in terms of both friction and wear.

Chemical composition of carrageenan blends determined by IR spectroscopy combined with a PLS multivariate calibration method.

The content of kappa, iota and lambda carrageenan in mixtures was determined by application of FT-IR spectroscopy combined with partial least-squares multivariate regression (PLS). This method allows the determination of the relative amounts of the different carrageenans in a rapid and accurate manner.

Dicationic ionic liquids as lubricants

Twelve dicationic ionic liquids have been investigated for their potential inlubricants. The dications selected were synthesized from oligoethylene glycols linking two cationic moieties based on either N-methylimidazolium or N-methylpyrrolidinium at the extremities. As anions, chloride, bis(trifluoromethanesulfonyl)imide (Tf2N), methanesulfonate and butansulfonate were chosen. Thermal stability of the IL has been evaluated by thermogravimetric analysis and differential scanning calorimetry showing good properties up to 150 °C for all IL. SRV tribotests of neat IL using steel–steel contacts with ball-on-disc geometry were performed at 50 °C, 100 °C and 150 °C. Friction and wear were significantly influenced by both anion structure and chain length of the oligoethylene glycol moiety where longer chains yielded better tribological behavior. The tribological behavior improved with a mixture of different types of ILcontaining F, O, S in their anions. A large variation of ionic liquids corrosiveness and corrosion inhibition, respectively, was found attributed to structure variation. A general tendencyof improving the corrosion resistance when increasing the chain length of the neat ILshas been found. In addition to the neat dicationic ionic liquids, mixtures of 1% of the mostinteresting IL in polypropylene glycol base oil have been studied at 100 °C resulting in more favorable tribological properties for ionic liquids with Tf2N anion. X-ray photoelectron spectroscopy analysis showed that the structures with Tf2N anion create a tribofilm of inorganic fluorine that greatly improves the performance of the base oil.