Sonication-assisted extraction of Hibiscus sabdariffafor the polyphenols recovery: application of a specially designed deep eutectic solvent

Sonication-assisted extraction has been used to extract bioactive substance from Hibiscus sabdariffa. Deep eutectic solvent was specially designed by mixing and heating citric acid (hydrogen bond acceptor) and ethylene glycol (hydrogen bond donor). The process conditions (amplitude of the ultrasound, extraction time, and water level in the solvent) of the sonication-assisted extraction were optimized by a statistical experimental design (Box-Behnken) through response surface method. Total polyphenol amount was the dependent variable, where its maximum yield has been calculated to be 22.77 mg gallic acid equivalent per dried matter under the optimum conditions (≈ 32% of amplitude, ≈ 43 min of extraction time, and ≈ 50% (v/v) water in deep eutectic solvent). The most effective parameter was found to be water content. Furthermore, the kinetic study of the extraction process has been also carried out by using second-order and film theory models. Effective diffusivity (Deff) under various conditions was also evaluated. The last but not the least, the products obtained by using the current advanced solvent were stored at different stresses in order to monitor the stability of polyphenol profile.