Polyphenol extraction from Origanum dictamnus using low-transition temperature mixtures composed of glycerol and organic salts: Effect of organic anion carbon chain length

Abstract

ABSTRACTNovel low-transition temperature mixtures (LTTMs), composed of glycerol and sodium acetate, sodium propionate, and sodium butyrate, were synthesized with the aim to investigate the organic anion chain length effect on the performance of polyphenol extraction from the medicinal plant Origanum dictamnus. The LTTMs used as hydrogen bond donor:hydrogen bond acceptor molar ratio of 6:1 and after establishing optimal conditions of water content and liquid-to-solid ratio by response surface methodology, kinetics was performed to identify the highest efficient system. The results drawn indicated that the longer the anion chain length, the higher the requirement for water content to achieve optimal total polyphenol yield. Extractions with LTTMs comprising of sodium propionate and sodium butyrate gave virtually equal yields in total polyphenols, yet extraction with the former solvent was significantly less energy-demanding, with the activation energy being 8.77 kJ mol−1. Liquid chromatography-diode array-mass spectrometry analyses revealed that the extract obtained with glycerol/sodium propionate at 70 °C also displayed a richer polyphenolic profile, while the antioxidant activity of the extract was not negatively affected up to this temperature. This novel green solvent is therefore proposed as a highly efficient means of recovering bioactive polyphenols from plant material.