Organic-NaH2PO4-H2O aqueous biphasic system for extraction of paeonol from cortex moutan: Solvent selection and mechanism probing

Aqueous biphasic system (ABS) for extraction of active components attracted increasing attention due to advantages of high extraction efficiency and high product purity. However, solvent factors ruling extraction is still unclear. Four new ABSs with different organic solvent were designed for paeonol extraction, and the extraction conditions such as NaH2PO4 concentration, organic solvent fraction, extraction period and temperature were examined with single factor method. The paeonol extraction yield, partition coefficient and paeonol purity with ABSs at optimized conditions were in the order as follows: ABS-THF-EA (33.6 +/- 1.5 mg/g) approximate to ABS-Ac-EA (33.0 +/- 1.3 mg/g) > ABS-EtOH-EA (31.6 +/- 1.6 mg/g)approximate to 70 % ethanol (v/v) (31. 2 +/- 1.4 mg/g) > ABS-THF (28.8 +/- 1.0 mg/g) > ABS-Ac (27.6 +/- 1.2 mg/g) > ABS-EtOH (25.2 +/- 1.2 mg/g), suggesting that replacing fraction of acetone/THF with ethyl acetate (EA) in ABSs could improve paeonol yield. Compositions and solvatochromic parameters for top phase of 12 ABSs were detected. Using LSER model, paeonol yield was strongly correlated to the dipolarity/dipolarizability (pi*), hydrogen bond acidity (alpha) and hydrogen bond basicity (beta) of top-phase medium in ABS (r(2) = 0.982, n = 12); and partition coefficient was reasonably correlated to pi*, alpha and beta (r(2) = 0.942, n = 12). Hydrogen-bond interaction and hydrophobicity interaction between paeonol and top-phase medium were crucial for efficient extraction. Solvatochromic parameters can offer guidance to solvent selection in extraction with ABS. (C) 2022 Elsevier B.V. All rights reserved.

Automated summary

Aqueous biphasic systems (ABSs) have gained increasing attention for the extraction of active components due to their high extraction efficiency and product purity. This study investigated the solvent factors influencing extraction by designing four new ABSs with different organic solvents for paeonol extraction. The results showed that replacing acetone/thf with ethyl acetate (EA) in ABSs improved the paeonol yield. Furthermore, the solvatochromic parameters of the top phase in ABSs were detected, and it was found that the dipolarity/dipolarizability, hydrogen bond acidity, and hydrogen bond basicity of the top phase medium were strongly correlated with paeonol yield and partition coefficient. These findings highlight the importance of hydrogen bonding and hydrophobic interactions in efficient extraction, and the solvatochromic parameters can provide guidance for solvent selection in ABS extraction.