A natural deep eutectic solvent (NaDES) composed of levulinic acid and glucose using a molar ratio of 5 : 1 (molHBA:molHBD) and 20% of water (w/w) (LeG_5_20) was found as a great alternative to the commonly used organic solvents for the extraction of hydroxynaphthoquinone enantiomers (HNQs) from Alkanna tinctoria (L.) Tausch roots. In the present work, a comparative investigation of recovery methods for HNQs, such as solid-phase extraction, macroporous resin, and water as an anti-solvent, was performed to face the main disadvantage of NaDES: the inability to be evaporated. The highest recovery of HNQs was recorded using the solid-phase extraction on a reversed-phase C8 cartridge with a total hydroxynaphthoquinone content (TNC) of 46.79 ± 0.952 mg/g of dry weight (DW). In addition, a great recovery of HNQs was also reported for the macroporous resin Amberlite XAD 4 with a TNC value of 37.21 ± 1.789 mg/g DW, while the precipitation of HNQs by using water as an anti-solvent (1 : 5, v/v) offered a TNC value of 28.68 ± 0.023 mg/g DW. The macroporous resin Amberlite XAD also showed a great potential for larger-scale applications. In fact, the developed scale-up process, involving Amberlite XAD 4, showed a great recovery efficiency for HNQs (34.126 ± 1.093 mg/g DW), an acceptable robustness (RSD < 15%), and the possibility of recycling LeG_5_20 with a recovery greater than 50%; therefore, it is an excellent green alternative extraction procedure for HNQs.

中文翻译：

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从天然深共熔溶剂中回收 Alkanna tinctoria （L.） 的羟基萘醌对映异构体的技术：比较分析

发现一种由乙酰丙酸和葡萄糖组成的天然低共熔溶剂 （NaDES），摩尔比为 5：1 （molHBA：molHBD） 和 20% 的水 （w/w） （LeG_5_20） 是常用有机溶剂的良好替代品，用于从 Alkanna tinctoria （L.） Tausch 根中提取羟基萘醌对映异构体 （HNQ）。在本工作中，对 HNQs 的回收方法进行了比较研究，例如固相萃取、大孔树脂和水作为反溶剂，以应对 NaDES 的主要缺点：无法蒸发。在总羟基萘醌含量 （TNC） 为 46.79 ± 0.952 mg/g 干重 （DW） 的反相 C8 小柱上使用固相萃取记录了 HNQs 的最高回收率。此外，据报道，大孔树脂 Amberlite XAD 4 的 HNQs 回收率也很高，TNC 值为 37.21 ± 1.789 mg/g DW，而使用水作为抗溶剂沉淀 HNQs （1 ： 5， v/v） 的 TNC 值为 28.68 ± 0.023 mg/g DW。大孔树脂 Amberlite XAD 也显示出更大规模应用的巨大潜力。事实上，涉及 Amberlite XAD 4 开发的放大工艺显示出对 HNQs 的高回收效率 （34.126 ± 1.093 mg/g DW）、可接受的稳健性 （RSD < 15%），以及回收率大于 50% 的回收LeG_5_20的可能性;因此，它是 HNQs 的优秀绿色替代提取程序。