A comparative study of lupeol extraction from a by-product of lupin processing by hydrophobic natural deep eutectic solvents and their precursor components

Abstract

A series of hydrophobic natural deep eutectic solvents (HNADESs) have been employed to extract lupeol from lupin seed coat at 30 and 70°C. The extraction yields have been compared with those obtained with conventional organic solvents. In general, lupeol extraction yields (LEYs) obtained when using HNADES are somewhat smaller than those obtained if organic solvents are used. However, the nature of the HNADES mixtures as green solvents represents a superior performance in terms of sustainability of the extraction process. Additionally, an investigation has been carried out in order to compare the LEYs obtained when using the HNADES mixtures with those obtained if the isolated precursor compounds are employed at a temperature (70°C) where both HNADES and the corresponding precursor compounds are liquids. Surprisingly, LEYs for lupeol at 70°C were found to be, in some cases, slightly higher if the precursor compounds are used in comparison with the proper HNADES mixtures. It seems that the unique properties of the HNADES mixtures are not enough to perform better as extractants in comparison with the isolated precursor compounds at moderate temperatures, at least for the case of lupeol from lupin seed coat. Some hints are presented to explain these results.

[Practical Applications]: The demand to use by-products, such as raw materials, to obtain potential bioactive compounds is gaining strong attention in the last years. The use of green solvents to extract these compounds is also envisaged to obtain substances in an environment-friendly way and with high sustainability for the economy and end-consumers. The main aim of this work is the extraction of lupeol from lupin seed coat by using on one side different hydrophobic natural deep eutectic solvent (HNADES) mixtures, and on the other side by using the precursor compounds of the mixtures, in order to evaluate the efficiency of these green extraction solvents in the recovery of bioactive compounds with health benefits from waste material. Our results show that lupeol can be extracted both with the HNADES mixtures and with their precursor components at moderate temperatures with similar efficiency. This work questions the need of using HNADES as clean extraction solvents as the precursor compounds have themselves interesting extracting capacities.