Natural Deep Eutectic Solvents: A platform to Boost Eucalyptus globulus and Quercus suber cork integrated Biorefineries

Funder

Organizational Unit

Publications

Optimization of the extraction of phenolic compounds from walnut leaves using DES.

Publication . Vieira, Vanessa; Prieto Lage, Miguel A.; Barros, Lillian; Coutinho, João A.P.; Ferreira, Olga; Ferreira, Isabel C.F.R.

Deep eutectic solvents (DES) are a new generation of alternative solvents resulting from the mixture of two (or more) starting materials where the eutectic temperature of the mixture is considerably lower than the melting point of the individual components [1]. DES can be considered “designer solvents” due to the possibility of combining different hydrogen bond acceptors and donors, to obtain solvents with specific affinity to the target molecules. Among their many applications is the potential use of DES as both solvents and formulation media of extracts rich in phenolic compounds [2]. In this work, the heat assisted extraction of phenolic compounds from walnut leaves was optimized, using DES based on choline chloride (CC) and carboxylic acids. To evaluate the response, the main phenolic compounds present in the extract (acid 3-O-caffeyloquinic acid, quercetin 3-O-glucoside and quercetin O-pentoside) were determined by HPLC-DAD. From a preliminary solvent screening, butyric acid (BA) and phenylpropionic acid (PPA) were selected as hydrogen bond donors. The extraction conditions (time, temperature and water content) were then optimized by an experimental design, assisted by response surface methodology. Water content was the most relevant extraction variable, followed by temperature and, lastly, extraction time. Under the optimized conditions, it was possible to obtain a response of 37.9±4.0 mg/g dw for CC:BA and 31.7±4.2 mg/g dw, for CC:PPA. Compared to the traditional water + ethanol reference solvent, similar or higher extraction yields were obtained using the selected DES.

2017Conference object

Open access

Polyols based solvents for the extraction of phenolic compounds from Juglans regia L. leaves.

Publication . Vieira, Vanessa; Prieto Lage, Miguel A.; Barros, Lillian; Coutinho, João A.P.; Ferreira, Isabel C.F.R.; Ferreira, Olga

In this work, a set of polyols was selected to be used as solvents for the extraction of phenolic compounds from Juglans regia L. (walnut) leaves. Their biocompatibility and low toxicity makes them an interesting option with potential industrial applications in the cosmetic, pharmaceutical or food areas. In fact, some of them are already used as cosmetic ingredients and/or can be obtained from renewable raw materials [1, 2]. Walnut leaves are an important source of bioactive molecules, such as phenolic compounds, suggesting that their extracts (or pure components) could be used as natural antioxidants in different applications, e.g. to replace synthetic antioxidants such as BHT (2,6-di-tert-butyl-4-methylphenol) or in dermatological bases preventing oxidative damage [3,4]. Hence, the extraction performance of glycerol and a series of diols (1,2-etanodiol, 1,2-propanediol, 1,3- propanediol, 1,3-butanediol, 1,2-pentanediol, 1,5-pentanediol, 1,2-hexanediol, 1,6-hexanediol) was screened and the phenolic profile, characterized by HPLC-DAD. To evaluate the response, only the main bioactive compounds present in the extract (acid 3-O-caffeyloquinic acid, quercetin 3-O-glucoside and quercetin O-pentoside) were considered. In a second phase, for comparison purposes, the most promising polyols were selected to prepare betaine based deep eutectic mixtures. After selecting the best solvent, the remaining extraction conditions (time, temperature and water content) were further optimized. These results provide relevant information for the design of an extraction process of phenolic compounds from J. regia leaves using alternative solvents that could also play a role as a formulation medium.

2017Conference object

Open access

Design and Characterization of Sugar-Based Deep Eutectic Solvents Using Conductor-like Screening Model for Real Solvents

Publication . Silva, Liliana P.; Fernandez, Luis; Conceição, João H.F.; Martins, Mónia A.R.; Sosa, Adriel; Ortega, Juan; Pinho, Simão; Coutinho, João A.P.

Inspired by the lack of characterization of natural eutectic and deep eutectic (DES) systems, we studied the solid-liquid equilibria (SLE) of binary and ternary mixtures involving choline chloride and sugars. The densities, viscosities and solvatochromic parameters for the binary systems containing choline chloride, [Ch]Cl, were measured at the eutectic composition, and the water impact on these properties was also investigated in order to address the tailoring of their properties using water. Mixtures of sugars are shown to present an ideal behavior, while their binary mixtures with choline chloride present negative deviations to the ideality, particularly in the sugar solubility curve. Aiming to develop a predictive model to design new sugar based DES, the [Ch]Cl + sugars phase diagrams were used to tune the COnductor-like Screening MOdel for Real Solvents (COSMO-RS) parameters, which was after applied in the estimation of the eutectic points of new ternary DES. The predictions quality was checked experimentally, proving that COSMO-RS can be a useful tool for the design of deep eutectic solvents.

2018Journal article

Open access