Ecotoxicity studies of the levulinate ester series

Nature of a Tetrabutylammonium Chloride-Levulinic Acid Deep Eutectic Solvent

A deep eutectic solvent was formed by considering the mixtures of tetrabutylammonium chloride and levulinic acid, and it is studied via a combined theoretical and experimental approach. Physicochemical properties were measured as a function of temperature, providing a macroscopic characterization of the fluid. Quantum chemistry and classical molecular dynamics simulations were carried out for the nanoscopic characterization, providing attention to the nature, extension, and dynamics of the hydrogen bonding network, which is at the root of the properties of the fluid. The reported study allows multiscale characterization of this fluid as an archetypical example of a natural, low-cost, and sustainable fluid.

Ecotoxicological study of glucose:choline chloride and sorbitol:choline chloride at different contents of water

The search of new solvents is currently focused on deep eutectic solvents (DES). However, there are not many ecotoxicological studies in different biomodels of DES that allow knowing how these chemicals affect to the environment along the trophic chain. In this manuscript, two DES at different proportion of water have been prepared and characterized from the ecotoxicological point of view. These solvents are glucose:choline chloride (2:5) and sorbitol:choline chloride (3:2) at different contents of water. To carry out the ecotoxicological study, three biomodels have been used: bacteria Aliivibrio fisheri (A. fisheri), crustacean Daphnia magna (D. magna) and algae Raphidocelis subcapitata (R. subcapitata). The obtained results show that the ecotoxicity of these chemicals depends on the biomodel used and the amount of water, being toxicity values lower for chemicals with higher water content. However, it is important to highlight that the ecotoxicity for all chemicals is quite low with effective concentrations, EC₅₀ values above 1000 mg/L in all the studied cases.

Alkyl Levulinates and 2-Methyltetrahydrofuran: Possible Biomass-Based Solvents in Palladium-Catalyzed Aminocarbonylation

In this research, ethyl levulinate, methyl levulinate, and 2-methyltetrahydrofuran as bio-derived hemicellulose-based solvents were applied as green alternatives in palladium-catalyzed aminocarbonylation reactions. Iodobenzene and morpholine were used in optimization reactions under different conditions, such as temperatures, pressures, and ligands. It was shown that the XantPhos ligand had a great influence on conversion (98%) and chemoselectivity (100% carboxamide), compared with the monodentate PPh₃. Following this study, the optimized conditions were used to extend the scope of substrates with nineteen candidates (various para-, ortho-, and meta-substituted iodobenzene derivatives and iodo-heteroarenes), as well as eight different amine nucleophiles.

Sulfated Well-Defined Mesoporous Nanostructured Zirconia for Levulinic Acid Esterification

Well-organized zirconia (ZrO₂) nanoparticles forming mesoporous materials have been successfully synthesized via a facile micelle-templating method using cetyltrimethylammonium bromide as a structure-directing template to control the nucleation/growth process and porosity. The systematic use of such a surfactant in combination with a microwave-assisted solvothermal (cyclohexane/water) reaction enabled the control of pore size in a narrow-size distribution range (3-17 nm). The effect of solvent mixture ratio on the porosity of the synthesized oxide was determined, and the controlled growth of zirconia nanoparticles was confirmed by means of powder X-ray diffraction, small-angle X-ray scattering, transmission electron microscopy, selected area electron diffraction, high-resolution transmission electron microscopy, X-ray photoelectron spectroscopy, thermogravimetric analysis, and Fourier transform infrared spectroscopy as well as N₂ physisorption isotherm analysis. Then, the as-prepared nanostructured zirconia oxides were treated with sulfuric acid to have sulfated samples. The catalytic performances of these mesoporous zirconia nanoparticles and their sulfated samples were tested for levulinic acid (LA) esterification by ethanol, with quantitative conversions of LA to ethyl levulinate after 8 h of reaction.

Ecotoxicity interspecies study of ionic liquids based on phosphonium and ammonium cations

This work studies the effects of different bromide-based ionic liquids, with phosphonium and ammonium cations, towards several environmental biomodels: Daphnia magna, Allivibrio fischeri, Raphidocelis subcapitata. Results indicate that toxicity clearly depends on the biomodel, Allivibrio fischeri being the least sensitive one while Daphnia magna is more severely affected in the presence of the studied ionic liquids. In most of the cases, phosphonium moieties are less toxic than ammonium ionic liquids. Furthermore, a prediction about the oral toxicity and carcinogenicity of the studied ionic liquids has been also carried out, showing that these chemical structures may suggest significant toxicity but not present genotoxic or nongenotoxic carcinogenicity.

Deep Eutectic Solvents: Are They Safe?

Deep eutectic solvents (DESs) are a relatively new type of solvent that have attracted the attention of the scientific community due to their environmentally friendly properties and their versatility in many applications. Many possible DESs have been described and, thus, it is not easy to unequivocally characterize and generalize their properties. This is especially important in the case of the (eco)toxicity information that can be found for these mixtures. In this review, we collect data on the human and environmental toxicity of DESs, with the aim of gathering and exploring the behavioral patterns of DESs. The toxicity data found were analyzed attending to different factors: hydrogen bond donors or acceptors that form part of the eutectic mixture, pH, and the presence of organic acids in the DES molar ratio of the components, or interactions with natural compounds. In the case of ecotoxicity, results generally depend on the biomodel studied, along with other factors that have been also revised. Finally, we also carried out a revision of the biodegradation of DESs.

Green toxicological investigation for biofuel candidates

To avoid potential risks of biofuels on the environment and human, ecotoxicity investigation should be integrated into the early design stage for promising biofuel candidates. In the present study, a green toxicology testing strategy combining experimental bioassays with in silico tools was established to investigate the potential ecotoxicity of biofuel candidates. Experimental results obtained from the acute immobilisation test, the fish embryo acute toxicity test and the in vitro micronucleus assay (Chinese hamster lung fibroblast cell line V79) were compared with model prediction results by ECOSAR and OECD QSAR Toolbox. Both our experimental and model prediction results showed that 1-Octanol (1-Oct) and Di-n-butyl ether (DNBE) were the most toxic to Daphnia magna and zebrafish among all the biofuel candidates we investigated, while Methyl ethyl ketone (MEK), Dimethoxymethane (DMM) and Diethoxymethane (DEM) were the least toxic. Moreover, both in vitro micronucleus assay and OECD QSAR Toolbox evaluation suggested that the metabolites present higher genotoxicity than biofuel candidates themselves. Overall, our results proved that this green toxicology testing strategy is a useful tool for assessing ecotoxicity of biofuel candidates.

QSAR modelling for predicting the toxic effects of traditional and derived biomass solvents on a Danio rerio biomodel

The increasing interest in the development of ecofriendly solvents has led to the synthesis of benign alternative chemicals with minimized environmental impacts. These kinds of chemicals are known as Green solvents. In this work, we selected three families of solvents (furfural, lactate and levulinate families) derived from biomass that are structurally related. Most of the previous ecotoxicological studies of these solvents have focused on invertebrate models such as bacteria, algae and crustaceans. To complete this information, in this work, the acute toxicity of these solvents was studied in Danio rerio (D. rerio). Sublethal and lethal effects were also observed, and the LC₅₀ was obtained. The LC₅₀ values ranged from 13.21 to 12073 mg L^-1, with furfural being the most toxic compound and tetrahydrofurfuryl alcohol the least toxic. Furthermore, the results indicated that a frequent sublethal effect was heart oedema or malformation, even in some cases at concentrations lower than the LC₅₀. A QSAR analysis was also performed to model the toxicological effect towards D. rerio for the studied solvents obtained from biomass and traditional solvents. A total of 15 molecular descriptors of the solvents were obtained using Gaussian 03 software. Finally, we also used the physicochemical property Log P, calculated from ACD/LogP, for QSAR modelling. Multivariable regression analysis showed that the minimum set of independent variables that leads to the best regression is Log P, the energy of the lowest unoccupied molecular orbital (ELUMO) and the heat capacity (CV). The proposed model was validated using several internal and external methods.

Exploring the usefulness of key green physicochemical properties: Quantitative structure-activity relationship for solvents from biomass

In recent decades there has been a growing interest in the development of new solvents from biomass. Some of these new solvents have been classified as green because of their renewable and sustainable source. However, characterization from the ecotoxicological and physicochemical points of view is needed to categorize them as green solvents. We have selected several key physicochemical properties that can reflect environmental features (density, boiling point, critical aggregation concentration, and log p) and explored their usefulness for preliminarily assessing the green character of the studied solvents. Specifically, we have studied several solvents from biomass: lactate family (methyl, ethyl, and butyl lactate), furfural family (furfural, 5-methylfurfural, furfuryl alcohol, and tetrahydrofurfuryl alcohol), and levulinate family (methyl, ethyl, and butyl levulinate). To fill the gaps and complete some toxicity data for the environment, we have measured the ecotoxicity using 2 of the most common and versatile biomodels, bacteria Vibrio fischeri and crustacean Daphnia magna, for furfural- and lactate-derived compounds. The results indicate that solvents from biomass can be categorized as green because their toxicity for the environment is low. Finally, a quantitative structure-activity relationship (QSAR) study was performed with the selected key properties and the ecotoxicological information. Despite the different structure of the chemicals under study, good correlations were found for the studied organisms. It seems that log p and critical aggregation concentration reflect the greatest part of the ecotoxic behavior, whereas density and boiling point cannot reflect toxicity signals. However, these properties are rather useful for assessing the final environmental fate of the studied chemicals. Environ Toxicol Chem 2018;37:1014-1023. © 2017 SETAC.

New Insights into the Reactivity of Biomass with Butenes for the Synthesis of Butyl Levulinates

This article reports a detailed study on the reactivity of levulinic acid and cellulose with 1-butene and iso-butene for the catalytic formation of sec- and tert-butyl levulinates. The influence of catalyst type and various solvent conditions have been investigated to assess the potential of a sustainable transformation. A very simple and efficient procedure was discovered by using reusable Amberlyst-15 in the absence of solvent to form, from levulinic acid and iso-butene, tert-butyl levulinate (70 % yield), a compound very difficult to prepare by other means. sec-Butyl levulinate (66 % yield) was obtained by using Amberlyst-15 in γ-butyrolactone as a biosourced solvent. The original procedure was also extended notably by directly using cellulose as a reactant. In the presence of a catalytic amount of H₂ SO₄ , it was possible to form sec-butyl levulinate (19 % yield) from 1-butene in a more efficient way than by using the alcohol as an esterifying agent.

Comparative ecotoxicology study of two neoteric solvents: Imidazolium ionic liquid vs. glycerol derivative

In this study we have compared the acute ecotoxicity of two solvents, with very different structure and origin, but sharing many physical-chemical properties, so they can be used for similar purposes; a well-known ionic liquid 1-butyl-3-methylimidazolium hexafluorophosphate ([BMIM][PF6]) and a solvent partially derived from biomass, 3-bis(2,2,2-trifluoroethoxy)propan-2-ol (BTFIP). We have used three biomodels (Vibrio fischeri, Daphnia magna and Danio rerio) and performed the comparison applying the Environmental, Health and Safety (EHS) hazard assessment. According to the results, ecotoxicity of [BMIM][PF6] and BTFIP is quite similar in the simplest model Vibrio fischeri, while in Daphnia magna [BMIM][PF6] is clearly more toxic. However, in Danio rerio, toxicity of these chemicals is again quite similar and both can be classified as "nontoxic". The higher index value of [BMIM][PF6] in water mediate effect in the EHS assessment indicates that this ionic liquid is more dangerous than BTFIP, although accumulation and degradation properties have not been taken into account. Further studies will be necessary to ascertain these conclusions.

Acute embryo toxicity and teratogenicity of three potential biofuels also used as flavor or solvent

The demand for biofuels increases due to concerns regarding greenhouse gas emissions and depletion of fossil oil reserves. Many substances identified as potential biofuels are solvents or already used as flavors or fragrances. Although humans and the environment may be readily exposed little is known regarding their (eco)toxicological effects. In this study, the three potential biofuels ethyl levulinate (EL), 2-methyltetrahydrofuran (2-MTHF) and 2-methylfuran (2-MF) were investigated for their acute embryo toxicity and teratogenicity using the fish embryo toxicity (FET) test to identify unknown hazard potentials and to allow focusing further research on substances with low toxic potentials. In addition, two fossil fuels (diesel and gasoline) and an established biofuel (rapeseed oil methyl ester) were investigated as references. The FET test is widely accepted and used in (eco)toxicology. It was performed using the zebrafish Danio rerio, a model organism useful for the prediction of human teratogenicity. Testing revealed a higher acute toxicity for EL (LC50: 83mg/L) compared to 2-MTHF (LC50: 2980mg/L), 2-MF (LC50: 405mg/L) and water accommodated fractions of the reference fuels including gasoline (LC50: 244mg DOC/L). In addition, EL caused a statistically significant effect on head development resulting in elevated head lengths in zebrafish embryos. Results for EL reduce its likelihood of use as a biofuel since other substances with a lower toxic potential are available. The FET test applied at an early stage of development might be a useful tool to avoid further time and money requiring steps regarding research on unfavorable biofuels.

Microscale In Vitro Assays for the Investigation of Neutral Red Retention and Ethoxyresorufin-O-Deethylase of Biofuels and Fossil Fuels

Only few information on the potential toxic effectiveness of biofuels are available. Due to increasing worldwide demand for energy and fuels during the past decades, biofuels are considered as a promising alternative for fossil fuels in the transport sector. Hence, more information on their hazard potentials are required to understand the toxicological impact of biofuels on the environment. In the German Cluster of Excellence "Tailor-made Fuels from Biomass" design processes for economical, sustainable and environmentally friendly biofuels are investigated. In an unique and interdisciplinary approach, ecotoxicological methods are applied to gain information on potential adverse environmental effects of biofuels at an early phase of their development. In the present study, three potential biofuels, ethyl levulinate, 2-methyltetrahydrofuran and 2-methylfuran were tested. Furthermore, we investigated a fossil gasoline fuel, a fossil diesel fuel and an established biodiesel. Two in vitro bioassays, one for assessing cytotoxicity and one for aryl hydrocarbon receptor agonism, so called dioxin-like activity, as measured by Ethoxyresorufin-O-Deethylase, were applied using the permanent fish liver cell line RTL-W1 (Oncorhynchus mykiss). The special properties of these fuel samples required modifications of the test design. Points that had to be addressed were high substance volatility, material compatibility and low solubility. For testing of gasoline, diesel and biodiesel, water accommodated fractions and a passive dosing approach were tested to address the high hydrophobicity and low solubility of these complex mixtures. Further work has to focus on an improvement of the chemical analyses of the fuel samples to allow a better comparison of any effects of fossil fuels and biofuels.

Readily biodegradable and low-toxic biocompatible ionic liquids for cellulose processing

Ecotoxicity and biodegradability of ILs intended for cellulose processing were tested. Betaine-ester levulinate exhibits low environmental hazard potential (full degradability, low toxicity). Other ILs were partially degradable and moderately toxic.