Mechanochemistry assisted aqueous two-phase extraction: an efficient technique to extract high-purity juglone from the bark of Juglans mandshurica

The bark of Juglans mandshurica (BJM) is a Chinese herbal medicine containing a variety of nutrients and pharmacologically active compounds. Juglone, one of the important active ingredients in BJM, has been shown by many pharmacological studies to have antioxidant, antibacterial, antiviral, anti-tumor, immunoregulatory and other pharmacological properties. Mechanochemistry assisted aqueous two-phase extraction (MAATPE) was successfully established to extract juglone from BJM, combining the purification effect of an alcohol/salt aqueous two-phase system (ATPS) with the high efficiency of mechanochemistry. The key parameters of MAATPE were systematically optimized through single factor analysis and response surface methodology. Under the optimal conditions of an ethanol/NaH₂PO₄ aqueous two-phase system as the liquid reagent, 21.5% (w/w) ethanol concentration, 28% (w/w) NaH₂PO₄ concentration, 458 rpm milling speed, 14 min milling time and 59 mL g⁻¹ reagent–material ratio, the maximum yield of juglone was 15.36 ± 0.16 mg g⁻¹ with a purity of 9.82 ± 0.12% in dry extracts. Compared with other extraction methods, it was found that MAATPE can not only improve the extraction efficiency of juglone, but also achieve higher juglone purity in the products. Finally, the mechanism of action, recyclability and industrial scalability of MAATPE are discussed. In conclusion, MAATPE is an appropriate alternative for the efficient preparation of high-purity products from natural resources.