Deep Eutectic Solvents Extraction of Polyphenol from the stem of Broccoli :Optimization, Components , and Antioxidant Activity

The stem of broccoli has been reported to contain high levels of polyphenols and other active compounds.To extract polyphenol from broccoli stem more efficiently, a novel procedure of deep eutectic solvent extraction (DESE) was proposed in this paper.The extraction process was optimised by response surface methodology. The optimum extraction parameters to obtain the highest yield of polyphenol 5.10 ± 0.04 mg/g from broccoli stem powder via choline chloride-urea (molar ratio 1:3) were obtained at liquid-solid ratio of 41:1 mL/g, water content of 60%, extraction temperature of 80°C and extraction time of 55 min. The components of the main polyphenol were identified by high-performance liquid chromatography-electrospray ionisation-mass spectrometry (HPLC-ESI-MS/MS).Compositional analysis shows that the extracted polyphenols are rich, including quercetin, isochlorogenic acid, trans-cinnamic acid and sinapinic acid. Furthermore, in vitro tests proved that the extracted polyphenols obtained in (ChCl-urea) DES possessed excellent antioxidant activity.These results provided an effective and feasible method for the extraction and separation of polyphenols in broccoli stalks, providing some technical support and theoretical basis for the green extraction of broccoli waste stalks.