Extraction of phenolic compounds from Sargassum muticum using deep eutectic solvents by conventional solid-liquid extraction, ultrasound and microwave-assisted extraction techniques

Bárbara Cristina Moutinho de Jesus

Key information

Authors:

Bárbara Cristina Moutinho de Jesus (Bárbara Cristina Moutinho de Jesus)

Supervisors:

Isabel Maria Delgado Jana Marrucho Ferreira (Isabel Maria Delgado Jana Marrucho Ferreira); Maria Gonzalez Miquel

Published in

12/02/2022

Abstract

Seaweeds are naturally abundant and invasive They have several biologically active secondary metabolites of great interest. Therefore, the interest of their exploitation has increased over the years. In this work Sargassum muticum was the algae employed as biomass and the aim was to extract phenolic compounds (PCs) using green extraction solvents. Several betaine-based, proline-based, and choline-based (deep) eutectic solvents ((D)ESs) were tested for the extraction of PCs. All extracts were evaluated according to the total phenolic content (TPC), total flavonoids content (TFC) and the antioxidant activity. Followed by the HPLC quantification of 9 PCs (gallic acid, 3,4 Dihydroxybenzoic acid, caffeic acid, syringic acid, p-coumaric acid, ferulic acid, salicylic acid, catechin and quercetin). There were a few (D)ESs that showed higher efficiency in comparison with conventional extraction solvents also evaluated. Proline combined with propylene glycol (Pro:PPG) was the best (D)ES according to HPLC results, followed by proline:1,2-butanediol (Pro:1,2-But) and choline:citric acid (ChCl:CA). Pro:PPG presented high selectivity towards the salicylic acid and ChCl:CA towards the gallic acid. Optimizations studies of water content and temperature were performed for the three best (D)ESs, being the optimum conditions at 30%(v/v) of water and 60ºC of extraction temperature. Ultrasound and Microwave assisted extractions were two intensification methods tested and they improved the extraction by significantly reducing the extraction time when compared with the conventional solid-liquid extraction even though the extraction yield could be slight lower. The exception was Pro:PPG with MAE where the extraction was significantly higher in comparison with the conventional extraction.