Recovery of chlorogenic acid from the DES-based extract of Eucommia ulmoides leaves by molecularly imprinted solid-phase extraction

To develop new ideas about the recovery of target components from the deep eutectic solvent (DES)-based extract, molecularly imprinted polymers (MIPs) were adopted as fillers for the solid-phase extraction to recover the chlorogenic acid (CGA) from the DES-based extract of Eucommia ulmoides leaves (EULs). Specifically, the CGA was taken as a template molecule to combine with three functional monomers (methacrylic acid (MAA), acrylamide (AM), and 2-vinylpyridine (2-VP)), respectively, through bulk polymerization to form MIPs. Then, the interaction between the CGA and these monomers by computational simulation was studied. Results show that MAA-MIPs are highly selective, with high adsorption capacity (120.70 mg/g) and rate (reaching the adsorption equilibrium at 40 min). Their static and dynamic adsorption behaviors conform to the Langmuir model and quasi-second-order kinetic model, respectively. In addition, the adsorption properties of these polymers confirm the conclusion that the pre-assembly system of CGA-MAA has the most hydrogen bonds and the largest binding energy. The recovery of CGA from the DES-based extract of EULs by MAA-MIPs are optimized to obtain the optimal solid-phase extraction conditions, in which the CGA shows a recovery rate of 75.15% and a purity of 65.20%. Notably, the addition of water in the loading solution could break the interaction between the components and DES to effectively improve the recovery. MAA-MIPs, as fillers for the molecularly imprinted solid-phase extraction, can achieve the specific adsorption and recycling of the template molecule CGA, which provides new ideas for the separation and purification of target products from the DES-based extract.