Preparation and application of molecularly imprinted polymers for the selective extraction of naringin and genistein from herbal medicines

Flavonoids are a class of important bioactive chemical constituents in herbal medicines and the simple, fast and selective extraction of flavonoids from herbal samples is quite meaningful. In this study, a simple and selective sample pretreatment procedure coupling molecularly imprinted polymers and solid-phase extraction (MIPs-SPE) was developed for the extraction and purification of flavonoids from herbal medicine samples. MIPs for flavonoids were synthesized through a multi-step swelling and polymerization method, using 4-vinylpyridine as the functional monomer and ethylene glycol dimethacrylate as the cross-linker. Scanning electron microscopy, Fourier transform infrared spectroscopy and elemental analysis were used to characterize the structural features of the obtained MIPs. The recognition performance of the polymers was investigated and several parameters affecting the recognition performance were also studied including the pH value of the mobile phase, the ratio of acetonitrile, the column temperature, the injection volume and the flow-rate of the mobile phase. The results revealed that a relatively good mono-dispersity of MIPs was obtained, and the average size of the obtained polymers was about 3–5 μm. Under the optimum recognition conditions, the obtained MIPs were successfully employed as selective adsorbents for SPE for the specific recognition and purification of flavonoids from herbal medicine samples.