Cubosomic supramolecular biosolvents based on monolaurin: Synthesis, characterization and potential for extraction of bioactives from spent coffee grounds and courgette peels

Abstract

Bioactive compounds are among the most valuable ingredients in agri-food residues but their efficient and sustainable extraction remains the major challenge to be overcome. Here, supramolecular biosolvents (bioSUPRASs) were firstly synthesized from the sulphate-induced self-assembly and coacervation of monolaurin in mixtures water-1-propanol, with the aim of providing more efficient and sustainable extraction processes in agri-food residue valorization. The incorporation of monolaurin into the bioSUPRAS was above 98%, making the synthesis selective and with high atom-economy. The bioSUPRASs were made up of monolaurin, water and 1-propanol and their chemical composition could be tailored by modifying the relative proportion of ingredients in the synthesis solution. The study of bioSUPRASs by cryo-scanning electron microscopy and Fourier transform infrared spectroscopy determined that monolaurin self-assembled in cubosomic nanostructures with water molecules surrounding the amphiphilic polar groups. Their applicability for extraction of bioactive compounds from agri-food residues was investigated, as a proof of concept, by extracting polyphenols and carotenoids in spent coffee grounds (SCG) and courgette peels. Major benefits of the use of monolaurin-based bioSUPRASs in these applications were: (1) both polyphenols and carotenoids were simultaneously and efficiently extracted, whereas polar and nonpolar conventional solvents are required to extract polyphenols and carotenoids, respectively. (2) Extractions occurred under mild conditions (room temperature and stirring for 15 min) whereas high temperatures (40–200 C) and/or extraction times (up to 3 h) were required using conventional solvents. (3) All bioSUPRAS ingredients are permitted by the cosmetic industry, so the bioSUPRAS extracts containing the bioactives could be used directly for the production of formulations.