NADES as potential solvents for anthocyanin and pectin extraction from Myrciaria cauliflora fruit by-product: In silico and experimental approaches for solvent selection

Abstract

In this work, in silico and experimental approaches were combined for the selection of starting compounds of NADES (Natural Deep Eutectic Solvents) aiming a selective and sequential extraction of anthocyanin and pectin from Myrciaria cauliflora by-product. Six NADES were prepared and characterized by DSC, pH, and rheological analysis. COSMO-RS was used to study the molecular contributions that confer affinity between NADES and target molecules. Besides, experimental solubility, extraction ability, and NADES cost were evaluated. DSC confirmed the formation of eutectic mixtures, which presented low pH values (0.77 to 4.01) and a wide range of apparent viscosity (0.070 to 36.922 Pa·s). The σ-profile [p(σ)], obtained by COSMO-RS, provided information on the polarity distribution of molecules and σ-potential [μ(σ)] curves was indicative of affinity between solute and solvent. According to in silico evaluation, both NADES and target compounds exhibit amphoteric character, indicating affinities between them. Acid-based NADES showed the highest affinity in the H-bond acceptor region while NADES content betaine and water presented the best affinities in the H-bond donor region. However, all NADES presented a low affinity for non-polar compounds. Choline chloride (ChCl):propylene glycol (Pro) were the most promising NADES for anthocyanin extraction and citric acid (Ca):glucose (Glu):water (Wa), for pectin. The proposed approach established a wise way to select NADES:water solutions as low-cost green solvents, aiming to achieve selective recoveries of value-added compounds.