Using COSMO-RS in the Design of Deep Eutectic Solvents for the Extraction of Antioxidants from Rosemary

Abstract

Trial and error remain the most common method to select the right solvent for the extraction of natural products, in particular when dealing with novel, poorly studied solvents such as deep eutectic solvents (DESs). This can lead to either a lengthy or a suboptimal selection of solvents. COSMO-RS, a quantum chemistrybased thermodynamic model, was applied in this work to screen the best DESs for the extraction of carnosic acid and carnosol, present in rosemary. Twenty-eight hydrogen bond acceptors (HBA) and fortynine hydrogen bond donors (HBD) were selected for the initial computational evaluation that revealed that hydrophobic DESs formed by ammonium chlorides as HBA, and the fatty acids, aromatic carboxylic acids, or alcohols as HBD to be the most suitable solvents for this extraction. Then, solid−liquid extractions were performed using these solvents to identify the best one and to optimize its composition. The ability of the solvents to obtain an extract rich in carnosic acid and carnosol was measured by the antioxidant activity of the extract, a mixture of 15 wt % of tetrapropylammonium chloride, 55 wt % of 1,2-propanediol, and 30 wt % of water being the solvent with the best performance. A response surface methodology was then carried out to optimize extraction conditions, in which antioxidant activity went up to 85 mg TE/g dw, that correspond to the extraction of 14.8 mg of carnosic acid and 18.9 mg of carnosol/g dw. Finally, the antioxidant activity of extracts obtained from a solvent without HBA was investigated. These aqueous mixtures of 1,2-propanediol showed a small loss in the performance. However, since the extraction process is simplified and this alcohol is biocompatible and allowed in formulations, the binary mixture seems to be a good, more sustainable alternative, to the ternary one.

COSMOtherm as an Effective Tool for Selection of Deep Eutectic Solvents Based Ready-To-Use Extracts from Graševina Grape Pomace

“…The search for the ideal DES for a given system has been so far guided by an empirical trial-and-error approach. Thus, to save time and money, and to reduce the experimental effort in searching for the most suitable solvent, we have herein applied in silico method–user-friendly software COSMOtherm [ 23 , 26 ]. Subsequently, the prepared extracts were chemically and biologically characterized.…”

“…The molar ratios of the DES forming compounds in each tested DES are listed in Table 1 . The lower activity coefficient of the tested HBA and HBD implies higher compound solubility [ 23 , 26 , 29 ].…”

“…The molar ratios of the DES forming compounds in each tested DES are listed in Table 1. The lower activity coefficient of the tested HBA and HBD implies higher compound solubility [23,26,29]. Figure 2 shows that there are ten different HBA with 20 HBD that can form different types of DES-from apolar to polar.…”

COSMO‐RS as an effective tool for predicting the physicochemical properties of fragrance raw materials

“…Therefore, it has been quite extensively used as a screening tool of extractive solvents as better/greener alternatives to the petroleum-based solvent n-hexane currently used for industrial extractions. [44][45][46][47][48] These investigations have highlighted ethyl acetate, dimethyl carbonate, cyclopentyl methyl ether, and 2-methyltetrahydrofuran as potential green alternative extraction solvents depending on the desired solute. 49,50 Polar solvents tend to extract more polar solutes, whereas non-polar solvents favor the extraction of hydrophobic ingredients, and polarity is well accounted for within COSMO-RS theory, allowing for quantitative prediction and comparison of solvents for a given solute.…”

Extraction of Chlorophylls and Carotenoids from Microalgae: COSMO‐SAC‐Assisted Solvent Screening

“…In the case of solvent extraction of microalgal compounds, the required proportions between the solvent and the solute renders the infinite dilution activity coefficient (IDAC) an important indicator, since selectivity and capacity at infinite dilution, which are functions of IDAC values, quantify the applicability of solvents and may be used for the purpose of screening 8. Among recently developed models, conductor‐like screening model (COSMO)‐based activity coefficient models have become an interesting alternative to the prediction of the behavior of substances in a mixture and have been employed with the aforementioned purpose 8–13. They are quantum chemistry‐based predictive equilibrium models in which the activity coefficient is calculated from the solvation‐free energy of the molecules in a solution 14.…”