Extraction and Preconcentration of the Main Target Polyphenols from Empetrum nigrum by Freeze-Ultrasonic Thawing Method Based on Synthetic Gemini Surfactant Aqueous Systems

Freeze-ultrasonic thawing extraction (FUTE) is a novel, green, and effective method for extracting bioactive compounds from plants, and the Gemini surfactant had the excellent properties especially for extracting hydrophobic and hydrophilic molecules. Therefore, the purpose of this study was to establish an effective method of synthetic Gemini surfactant aqueous system coupled with FUTE to extract the main individual polyphenols from the aerial parts of Empetrum nigrum. Based on identification of the polyphenols in the aerial parts of E. nigrum by ultra-high-performance liquid chromatography (UHPLC)–time of flight (TOF)–mass spectrometry (MS)/MS, the Gemini surfactant– N , N ʹ-bis(dodecyldimethyl)-1,4-butane dibromide (BBD)–FUTE technology was applied to extract the six main individual polyphenols. Under the optimum conditions, the extraction yields of neochlorogenic acid, catechin, rutin, hyperoside, quercetin, and guaijaverin were 8.48, 0.33, 4.23, 2.19, 1.12, and 0.32 mg/g, respectively, which were 1.01–1.96 and 1.15–2.39 times to those of ultrasonic-assisted extraction and freeze-thawing extraction methods, respectively. After cloud-point extraction, a preconcentration factor of 9.1 was obtained. All the results indicated that BBD-FUTE was a green and efficient method in the extraction of polyphenols from the aerial parts of E. nigrum . Therefore, it was suggested that the BBD-FUTE technology can be used as an alternative innovation method to effectively extract bioactive compounds from plant materials.