Extraction of phenolic compounds from black mustard ( Brassica nigra L.) seed by deep eutectic solvents

This study reports for the first time the total extractive matter yield, total phenolics and total flavonoids content (TPC and TFC, respectively), chemical composition, and ability to scavenging 2,2-diphenyl-1-picrylhydrazyl (DPPH) radicals of the black mustard seed (BMS) extracts obtained by deep eutectic solvents (DESs). The following DESs: triethanolamine:glycerol (TEOA:G), triethanolamine:propylene glycol (TEOA:PEG), and choline chloride:urea (ChCl:U), as well as their mixtures with water and ethanol at a ratio of 1:4 (v/v), were used. Their extraction efficiencies were compared with the efficiency of ethanol that is most frequently used to extract phenolic compounds from BMS. The TPC and TFC of the obtained extracts were in the ranges of 19.9 ± 0.1 to 32.2 ± 0.2 mg gallic acid equivalents/g and 3.9 ± 0.1 to 7.4 ± 0.3 mg quercetin equivalents/g, respectively. The BMS extracts obtained with the pure ChCl:U and the mixtures of ChCl:U or TEOA:G with ethanol showed the best antioxidant activity (IC 50 = 100 mg/mL). The obtained extracts contained syringic acid, ellagic acid, gallic acid, caffeic acid, caftaric acid, rutin, kaempferol, apigenin, taxifolin, hyperoside, and vitexin.