Preparation of a molecularly imprinted Poly(OA[AMI] supramolecular hydrogel) for selectively enriching oleanolic acid

Oleanolic acid possesses a wide variety of pharmacological activities and spreads in various plants, but always co-exist with its isomers ursolic acid. Separating oleanolic acid with high efficacy from ursolic acid contaminated plant extracts is quite important. This study prepared a molecularly imprinted poly(OA[AMI] supramolecular hydrogel) (MIPSHG@OA) for selectively enriching oleanolic acid, by using the 1-allyl-3-methylimidazolium oleanolic salt (OA[AMI]) as hydrogelator, template, functional monomer and basement. The preparation conditions were optimized as 12.5 mg OA[AMI], 40 mg MBA, 4 ml solvent, 10 mg APS, and 30 μl TEMED. The characterization by FT-IR spectra, TG analysis, SEM image and equilibrium swelling ratio showed a sheet and porous structure and a large equilibrium swelling ratio of the obtained MIPSHG@OA. The adsorption performance showed the obtained MIPSHG@OA was homogeneous on the surface and uniform on the adsorption sites, the adsorption of oleanolic acid on the polymers was chemisorption and monolayer, the adsorbed oleanolic acid molecules did not interact with each other, the MIPSHG@OA had high competitive recognition performance and imprinting efficiency on oleanolic acid, and had good recyclability. In the solid phase extraction application, the results demonstrated that the synthesized MIPSHG@OA could selectively enrich oleanolic acid.