Amido surface-functionalized magnetic molecularly imprinted polymers for the efficient extraction of Sibiskoside from Sibiraea angustata.

A general method for efficient and selective extraction of a target compound from complex natural products remains elusive, despite decades of research. By introducing a functional amido group on the surface of dispersity-enhanced magnetic nanoparticles, a nanoparticle receptor to selectively recognize Sibiskoside (a monoterpene) from the aerial portion of Sibiraea angustata by hydrogen bond interaction was synthesized. The superparamagnetic Fe₃O₄ nanoparticles were successively modified with tetraethyl orthosilicate (TEOS), amino and amido functional groups, and 4-vinylbenzoic acid (VBZA) was used as the functional monomer. A thin layer of poly (VBZA) imprinted with Sibiskoside was immobilized on the surface of magnetic carriers. Attributing to the amido group introduced into the magnetic particles, the template could attract and bind to the surface and promote the formation of a hydrogen bond system between the carrier, template molecules and functional monomer. High-density molecular recognition sites grew on the surface of magnetic substrate. The adsorption reached equilibrium at approximately 150 min, while fast adsorption occurred during the first 60 min. The maximum adsorption capacity has been found to be 13.75 mg g^-1 according to calculation with the Langmuir isotherm. The selectivity coefficients of Molecular imprinting polypers (MIPs) for Sibiskoside with respect to Andrographolide, Loganin, Gastrodin, geraniol-1-O-[α-l-rhamnopyranosyl-(1 → 6)-1-β-d-glucopyranoside] (GRG), Sibiscolacton and Sibiraic acid were 2.26, 1.43, 1.701.56, 1.05, 0.73 and, respectively. The results indicated that the MIPs possessed good specific adsorption capacity and selectivity toward Sibiskoside and had the potential to be a candidate for the separation and purification of monoterpenes from Sibiraea angustata, which is of great significance to obesity management.