Molecularly imprinted polymer for the specific solid-phase extraction of kirenol from Siegesbeckia pubescens herbal extract

Molecular imprinted polymers (MIPs) were prepared by thermal polymerization using a non-covalent molecularly imprinting strategy with kirenol as the template, acrylamide (AM) as the functional monomer and ethylene glycol dimethacrylamide (EGDMA) as the cross-linker in the porogen of tetrahydrofuran (THF). The synthesized MIPs were characterized by scanning electron microscopy (SEM) and Fourier transform infrared (FT-IR). Its molecular recognition property was investigated by UV spectrogram. High-pressure liquid chromatography (HPLC) was used for analysis of target analytes. The polymers were evaluated further by batch rebinding experiments, and from the derived isotherms their binding capacity and binding strength were determined. Then the selectivity of the MIPs was checked toward the selected structurally related compounds and the recognition coefficients for kirenol, darutigenol, and ent-2-oxo-15, 16, 19-trihydroxypimar-8(14)-ene (TD) were 2.47, 3.43 and 3.40, respectively. The properties of MIPs for SPE were also evaluated. The results obtained demonstrate that the good imprinting effect and the excellent selectivity of MIPs were obtained. The optimized molecular imprinted SPE procedure was applied to extract kirenol directly from the extracts of the aerial part of Siegesbeckia pubescens herb. A selective extraction of kirenol from traditional Chinese medicine (TCM) was achieved with extraction yield of 80.9%.