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A special issue of Molecules (ISSN 1420-3049). This special issue belongs to the section "Green Chemistry".

Deadline for manuscript submissions: closed (15 October 2018) | Viewed by 55495

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Prof. Dr. Giancarlo Cravotto

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Guest Editor

Department of Drug Science and Technology, University of Turin, via P. Giuria 9, 10125 Turin, Italy
Interests: enabling technologies ind food extraction and processing; microwaves; ultrasound; hydrodinamic cavitation; SC-CO₂; green solvents; bioactive natural products
Special Issues, Collections and Topics in MDPI journals

Prof. Dr. Andrioletti Bruno

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Université Claude Bernard Lyon 1, Bâtiment Lederer, 69622 Villeurbanne, CEDEX, France
Interests: green chemistry; synthesis; organometallic chemistry; biomass valorization; catalysis

Special Issue Information

Dear Colleagues,

The ideal solvent should address a number of requirements, including suitable physical and chemical properties, health safety, and a low environmental impact addressing regulatory concerns. Moreover, since 2007, solvents have been regulated at the European level under the Registration, Evaluation, Authorisation and Restriction of Chemicals regulation, known as REACH. In addition to intrinsic green properties and production from renewable resources, solvents sustainability also requires recovery procedures and reuse. Industry and academia have shifted their focus towards developing new bio-based solvents that are environmentally-friendly, as well as several combination on natural deep eutectic solvents. In the quest to achieve sustainability, leading solvent manufacturers have been collaborating with biotechnology firms to manufacture such greener solvents. This Special Issue is aimed at reporting recent advances in the field, and the new routes for green solvents toward industrial applications, highlighting, whenever possible, comparative aspects with classic organic solvents.

Prof. Dr. Giancarlo Cravotto
Prof. Dr. Andrioletti Bruno
Guest Editors

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Keywords

Green solvents
Bio-based solvents
Sustainable solvents
Extraction
Chemical processing.
Green solvent synthesis
Green solvent design
Uses
Extraction
Environmental impact

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Published Papers (10 papers)

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Research

11 pages, 1099 KiB

Open AccessArticle

Polyalcohols as Hydrogen-Bonding Donors in Choline Chloride-Based Deep Eutectic Solvents for Extraction of Xanthones from the Pericarp of Garcinia mangostana L.

by Kamarza Mulia, Farah Fauzia and Elsa Anisa Krisanti

Molecules 2019, 24(3), 636; https://doi.org/10.3390/molecules24030636 - 12 Feb 2019

Cited by 47 | Viewed by 6261

Abstract

Mangosteen (Garcinia mangostana L.) is a fruit that is rich in xanthones, utilized as health supplements or additives in food products due to their high antioxidant activities. Choline chloride (ChCl)-based deep eutectic solvents (DESs) with polyalcohols (ethylene glycol, glycerol, propanediols, and butanediols) as hydrogen bonding donors (HBDs) were used to extract the xanthones from the pericarp of mangosteen. DESs with 1,2-propanediol, 1,3-propanediol, and 1,2-butanediol as HBDs (ChCl to HBD mole ratio of 1:3) afforded the highest extraction yields (2.40-2.63%) of α-mangostin, the most abundant component that represents xanthones. These DESs have intermediate Nile Red polar parameter values similar to that of ethanol and provide extraction yields with a quadratic dependence on the polar parameter. Polarity and viscosity, the important physicochemical properties to consider in the selection of DES as an extraction solvent, could be adjusted based on the consideration of the molecular structure of the polyalcohols. The following factors qualifies the ChCl-1,2-propanediol DES as a designer solvent for green extraction: It is selected from a set of DESs having a homologous class of HBDs to deliver the highest α-mangostin extraction yield, its extract composition similar to that obtained using ethanol, it has low or negligible vapor pressure, both of its components are generally recognized as safe chemicals so that direct utilization of a DES extract is possible, and this DES is used for utilization of agricultural waste products as the resource of bioactive compounds. Full article

(This article belongs to the Special Issue Green and Sustainable Solvents)

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17 pages, 2723 KiB

Open AccessFeature PaperArticle

Antiproliferative, Proapoptotic, Antioxidant and Antimicrobial Effects of Sinapis nigra L. and Sinapis alba L. Extracts

by Valentina Boscaro, Luisa Boffa, Arianna Binello, Gabriella Amisano, Stefania Fornasero, Giancarlo Cravotto and Margherita Gallicchio

Molecules 2018, 23(11), 3004; https://doi.org/10.3390/molecules23113004 - 16 Nov 2018

Cited by 38 | Viewed by 6165

Abstract

High Brassicaceae consumption reduces the risk of developing several cancer types, probably due to high levels of glucosinolates. Extracts from Sinapis nigra L. (S. nigra) and Sinapis alba L. (S. alba) have been obtained from leaves and seeds under different conditions using ethanol/water mixtures because their glucosinolates are well accepted by the food industry. The EtOH/H₂O 8:2 mixture gives better yields in glucosinolate amounts from ground seeds, mainly, sinalbin in S. alba and sinigrin in S. nigra. The highest antiproliferative activity in both non-tumor and tumor cell lines was induced by S. alba seeds extract. To evaluate whether the effect of Sinapis species (spp) was only due to glucosinolate content or whether it was influenced by the extracts’ complexity, cells were treated with extracts or glucosinolates, in the presence of myrosinase. Pure sinigrin did not modify cell proliferation, while pure sinalbin was less effective than the extract. The addition of myrosinase increased the antiproliferative effects of the S. nigra extract and sinigrin. Antiproliferative activity was correlated to Mitogen-Activated Protein Kinases modulation, which was cell and extract-dependent. Cell-cycle analysis evidenced a proapoptotic effect of S. alba on both tumor cell lines and of S. nigra only on HCT 116. Both extracts showed good antimicrobial activity in disc diffusion tests and on ready-to-eat fresh salad. These results underline the potential effects of Sinapis spp in chemoprevention and food preservation. Full article

(This article belongs to the Special Issue Green and Sustainable Solvents)

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10 pages, 1778 KiB

Open AccessArticle

Optimization of the Synthesis of Glycerol Derived Monoethers from Glycidol by Means of Heterogeneous Acid Catalysis

by Elisabet Pires, José Ignacio García, Alejandro Leal-Duaso, José Antonio Mayoral, José Ignacio García-Peiro and David Velázquez

Molecules 2018, 23(11), 2887; https://doi.org/10.3390/molecules23112887 - 6 Nov 2018

Cited by 10 | Viewed by 3781

Abstract

We present an efficient and green methodology for the synthesis of glycerol monoethers, starting from glycidol and different alcohols, by means of heterogeneous acid catalysis. A scope of Brønsted and Lewis acid catalysts were applied to the benchmark reaction of glycidol and methanol. The selected catalysts were cationic exchangers, such as Nafion NR50, Dowex 50WX2, Amberlyst 15 and K10-Montmorillonite, both in their protonic form and exchanged with Al(III), Zn(II) and Fe(III). Thus, total conversions were reached in short times by using 1 and 5% mol catalyst loading and room temperature, without the need for excess glycidol or the presence of a solvent. Finally, these conditions and the best catalysts were successfully applied to the reaction of glycidol with several alcohols such as butanol or isopropanol. Full article

(This article belongs to the Special Issue Green and Sustainable Solvents)

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14 pages, 2200 KiB

Open AccessArticle

Lewis Acidity and Basicity of Mixed Chlorometallate Ionic Liquids: Investigations from Surface Analysis and Fukui Function

by Ying Liu and Juanfang Wang

Molecules 2018, 23(10), 2516; https://doi.org/10.3390/molecules23102516 - 30 Sep 2018

Cited by 11 | Viewed by 4417

Abstract

Mixed chlorometallate ionic liquids (ILs) have been regarded as potential solvents, catalysts, and reagents for many organic processes. The acidity and basicity of these ILs were correlated with theoretically estimated parameters such as electrostatic surface potential maxima and minima, average local surface ionization energy, and Fukui and dual descriptor functions. The introduction of metal chloride into the anions would influence the acidity/basicity of ILs by withdrawing the electron density from the cationic counterpart. For the [C₄mim]-based ILs with the mixed-metal anions, the acidity tends to attenuate while the basicity becomes stronger, as compared to the corresponding chloroaluminate ILs. However, the acidity of [(C₂H₅)₃NH]-based ILs with the mixed-metal anions are greater than that of the net chloroaluminate ILs. The Fukui function values showed that most of the mixed chlorometallate ILs belong to bifunctional distribution. The mixed chlorometallate ILs both have electrophilic and nucleophilic sites, which would be beneficial for their applications. Full article

(This article belongs to the Special Issue Green and Sustainable Solvents)

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14 pages, 5691 KiB

Open AccessFeature PaperArticle

Application of Ionic Liquid-Based Ultrasonic-Assisted Extraction of Flavonoids from Bamboo Leaves

by Liling Wang, Minge Bai, Yuchuan Qin, Bentong Liu, Yanbin Wang and Yifeng Zhou

Molecules 2018, 23(9), 2309; https://doi.org/10.3390/molecules23092309 - 10 Sep 2018

Cited by 41 | Viewed by 5128

Abstract

Ionic liquids (ILs), known as environmentally benign “green” solvents, were developed as an optimal solvent for the green extraction and separation field. In this paper, an ionic liquid-based ultrasonic-assisted extraction (IL-UAE) of flavonoids (FVs) from bamboo leaves of Phyllostachys heterocycla was developed for the first time. First, 1-butyl-3-methylimidazolium bromide ([Bmim] Br), with the best extraction efficiency, was selected from fifteen ionic liquids with diverse structure, like carbon chains or anions. Then, the influencing parameters of ionic liquid (IL) concentration, liquid-solid ratio, ultrasonic time, and ultrasonic power, were investigated by single factor tests, and further optimized using response surface methodology (RSM). In the optimization experiment, the best conditions were 1.5 mol/L [BMIM]Br aqueous solution, liquid-solid ratio 41 mL/g, ultrasonic time 90 min, and ultrasonic power 300 W. Furthermore, the microstructures of bamboo leaves and the recovery of FVs and [BMIM]Br were also studied. Therefore, this simple, green and effective IL-UAE method has potentiality for the extraction of FVs from bamboo leaves for the large-scale operations. Full article

(This article belongs to the Special Issue Green and Sustainable Solvents)

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11 pages, 1453 KiB

Open AccessArticle

Ionic Liquids: Efficient Media for the Lipase-Catalyzed Michael Addition

by Yunchang Fan, Dongxu Cai, Xin Wang and Lei Yang

Molecules 2018, 23(9), 2154; https://doi.org/10.3390/molecules23092154 - 27 Aug 2018

Cited by 9 | Viewed by 3703

Abstract

Recently, ionic liquids (ILs) have been regarded as ideal media for non-aqueous bio-catalysis. In this work, the synthesis of warfarin by the lipase-catalyzed Michael addition in IL media and the parameters that affected the warfarin yield were investigated. Experimental results demonstrated that the chemical structures of the ILs were a major factor for influencing the warfarin yield. The ILs containing the NTf₂^– anion were suitable reaction media due to the high chemical stability of this anion. The incorporation of the hydroxyl group on the IL cation significantly improved the lipase activity due to the H₂O-mimicking property of this group. The lipase activity decreased by increasing the alkyl chain length on the IL cation due to the non-polar domain formation of the IL cation at the active site entrance of lipase. The ILs and lipase could be reused no less than five times without reduction in the warfarin yield. Full article

(This article belongs to the Special Issue Green and Sustainable Solvents)

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13 pages, 2166 KiB

Open AccessArticle

Transesterification of Lactic Acid Oligomers with Ethanol, a Way to Anhydrous Ethyl Lactate: A Kinetic Study

by Silvestr Figalla, Jaroslav Petrůj and Tereza Švestková

Molecules 2018, 23(8), 2044; https://doi.org/10.3390/molecules23082044 - 15 Aug 2018

Cited by 4 | Viewed by 11161

Abstract

A new method for the preparation of anhydrous ethyl ester of lactic acid was studied. The selected method is based on catalytic transesterification of lactic acid oligomers, which were prepared for this purpose by autocatalytic oligomerization of lactic acid. In this work, a kinetic model for the case of catalytic alcoholysis of oligoesters was derived assuming a first-order reaction and equimolar content of reactants in the reaction mixture. The model makes it possible to obtain the values of the reaction rate and equilibrium constants and the equilibrium alcohol concentration by regression analysis at one time. The model was verified by measuring the rate of consumption of ethanol over the time at various reaction temperatures with anhydrous FeCl₃ as the catalyst. The reaction was studied at overpressure under autogenous conditions in the temperature range of 100–180 °C. For the catalyst concentration of 1 mol %, the activation energy value was 64.35 kJ·mol⁻¹. The dependence of equilibrium composition and rate constant on the temperature was obtained. The derived model is generally applicable to all first-order equilibrium reactions. The presumption is that the forward and reverse reactions are of the same order and have the same stoichiometry and equivalent amounts of reactants at the beginning of the reaction. Full article

(This article belongs to the Special Issue Green and Sustainable Solvents)

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17 pages, 1335 KiB

Open AccessArticle

Optimisation of Simultaneous Saccharification and Fermentation (SSF) for Biobutanol Production Using Pretreated Oil Palm Empty Fruit Bunch

by Nur Atheera Aiza Md Razali, Mohamad Faizal Ibrahim, Ezyana Kamal Bahrin and Suraini Abd-Aziz

Molecules 2018, 23(8), 1944; https://doi.org/10.3390/molecules23081944 - 3 Aug 2018

Cited by 28 | Viewed by 4014

Abstract

This study was conducted in order to optimise simultaneous saccharification and fermentation (SSF) for biobutanol production from a pretreated oil palm empty fruit bunch (OPEFB) by Clostridium acetobutylicum ATCC 824. Temperature, initial pH, cellulase loading and substrate concentration were screened using one factor at a time (OFAT) and further statistically optimised by central composite design (CCD) using the response surface methodology (RSM) approach. Approximately 2.47 g/L of biobutanol concentration and 0.10 g/g of biobutanol yield were obtained after being screened through OFAT with 29.55% increment (1.42 fold). The optimised conditions for SSF after CCD were: temperature of 35 °C, initial pH of 5.5, cellulase loading of 15 FPU/g-substrate and substrate concentration of 5% (w/v). This optimisation study resulted in 55.95% increment (2.14 fold) of biobutanol concentration equivalent to 3.97 g/L and biobutanol yield of 0.16 g/g. The model and optimisation design obtained from this study are important for further improvement of biobutanol production, especially in consolidated bioprocessing technology. Full article

(This article belongs to the Special Issue Green and Sustainable Solvents)

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15 pages, 3798 KiB

Open AccessArticle

Environmentally Friendly Approach to Knoevenagel Condensation of Rhodanine in Choline Chloride: Urea Deep Eutectic Solvent and QSAR Studies on Their Antioxidant Activity

by Maja Molnar, Harshad Brahmbhatt, Vesna Rastija, Valentina Pavić, Mario Komar, Maja Karnaš and Jurislav Babić

Molecules 2018, 23(8), 1897; https://doi.org/10.3390/molecules23081897 - 29 Jul 2018

Cited by 21 | Viewed by 5024

Abstract

A series of rhodanine derivatives was synthesized in the Knoevenagel condensation of rhodanine and different aldehydes using choline chloride:urea (1:2) deep eutectic solvent. This environmentally friendly and catalyst free approach was very effective in the condensation of rhodanine with commercially available aldehydes, as well as the ones synthesized in our laboratory. All rhodanine derivatives were subjected to 1,1-diphenyl-2-picrylhydrazyl radical (DPPH) scavenging activity investigation and quantitative structure-activity relationship (QSAR) studies were performed to elucidate their structure-activity relationship. The best multiple linear QSAR model demonstrate a stability in the internal validation and Y-randomization (R² = 0.81; F = 24.225; Q²_loo = 0.72; R²_Yscr = 0.148). Sphericity of the molecule, ratio of symmetric atoms enhanced atomic mass along the principle axes in regard to total number of atoms in molecule, and 3D distribution of the atoms higher electronegativity (O, N, and S) in molecules are important characteristic for antioxidant ability of rhodanine derivatives. Molecular docking studies were carried out in order to explain in silico antioxidant studies, a specific protein tyrosine kinase (2HCK). The binding interactions of the most active compound have shown strong hydrogen bonding and van der Waals interactions with the target protein. Full article

(This article belongs to the Special Issue Green and Sustainable Solvents)

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7 pages, 3085 KiB

Open AccessArticle

Sodium Copper Chlorophyllin Catalyzed Chemoselective Oxidation of Benzylic Alcohols and Diarylmethanes in Water

by Shi-juan Liu, Miao Zhang, Rong Lu, Xiu-ying Li and Guang-bo Che

Molecules 2018, 23(8), 1883; https://doi.org/10.3390/molecules23081883 - 27 Jul 2018

Cited by 4 | Viewed by 4261

Abstract

We report the highly efficient and chemoselective oxidation of benzylic alcohols catalyzed by sodium copper chlorophyllin in water, producing corresponding arylcarbonyl compounds. Importantly, the catalytic system exhibits a wide substrate scope and high functional group tolerance. Moreover, secondary alcohols and even diarylmethanes were [...] Read more.

(This article belongs to the Special Issue Green and Sustainable Solvents)

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