A range of natural deep eutectic solvents (NADESs) as separation‐free media were applied as extraction solvents in combination with ultrasound‐assisted extraction (UAE) for the extraction of hydroxytyrosol from olive fruits. Following the investigation of 7 different NADESs, a tailor‐made DES composed of malic acid and betaine (BeMa) in a 1 : 1 molar ratio was screened for its efficiency. High performance liquid chromatography (HPLC) was used to test the content of hydroxytyrosol in the extraction. Response surface methodology (RSM) combined with central composite design (CCD) was used for the experimental design. The optimum extraction efficiency was obtained using a 1 : 20 sample: solvent mass/volume ratio upon sonication for 33.65 min in an aqueous solution containing 42.13 % (w/v) DES at 43.86 °C. In addition, the zebrafish embryo toxicity test showed that the selected DES exhibited essentially no biotoxicity, while BeMa was found to increase the antibacterial ability of the target subject. Our results indicated that NADESs are promising as green and safe solvents for the extraction and analysis of active substances from natural plants.

中文翻译：

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超声辅助的天然深共晶溶剂作为橄榄中羟基酪醇的无分离萃取介质

多种天然深共熔溶剂（NADES）作为无分离介质，与超声波辅助萃取（UAE）结合使用，用于从橄榄果实中萃取羟基酪醇。在对7种不同的NADES进行研究后，由苹果酸和甜菜碱组成的量身定制的DES（BeMa以1∶1的摩尔比筛选其效率。高效液相色谱法（HPLC）用于测试提取物中羟基酪醇的含量。响应面方法（RSM）与中央复合设计（CCD）相结合用于实验设计。在43.86°C的含42.13％（w / v）DES的水溶液中超声处理33.65分钟后，使用1:20样品：溶剂质量/体积比，可获得最佳萃取效率。此外，斑马鱼胚胎毒性试验表明，所选的DES基本上没有生物毒性，而BeMa发现增加目标对象的抗菌能力。我们的结果表明，NADES作为绿色和安全的溶剂，有望用于从天然植物中提取和分析活性物质。