Extraction of weak hydrophobic sulforaphane from broccoli by salting-out assisted hydrophobic deep eutectic solvent extraction

In order to extract sulforaphane (SFN) from broccoli via green and efficient ways, a novel method based on salting-out assisted deep eutectic solvent (DES) has been developed. Compared to known organic solvent- (such as dichloromethane, ethyl acetate, n-hexane, etc.) based liquid–liquid extraction, this new N8881Cl-based DES method exhibited excellent extraction efficiency for SFN, including a significant improvement due to the salting-out effect of KH2PO4. Under optimal conditions, 97.77 % of SFN was extracted by N8881Cl-EG DES and more than 82.5 % of SFN was recovered by activated carbon from DES. In addition, further studies with Kamlet-Taft parameters and density functional theory showed that the H-bond accepting capacity of hydrophobic DES, the existing vdW interaction, and the electrostatic interaction between N8881Cl-EG DES all contributed to efficient extraction of SFN. This is the first time that the underlying mechanism for SFN extraction by DES was revealed.