No abstract

Despite the strong antihepatotoxic, antioxidant, and antitumor properties of lignans from Schisandra chinensis, their applications in new drug development, bioscience and functional foods, etc. are limited because of their low abundance and complex coextractions. In this study, a magnetic separation method has been developed based on polyethylenimine-modified magnetic nanoparticles to rapidly and effectively separate and purify the lignans from S. chinensis crude extracts through cation-π interaction and electrostatic adsorption. The magnetic nanoparticles were characterized by transmission electron microscopy, vibrating sample magnetometry, Fourier transform infrared spectroscopy, and X-ray diffraction. Polyethylenimine-modified magnetic nanoparticles showed a spherical-shaped morphology and the average size was about 10 nm with superparamagnetism. Under the pH 7.4, polyethylenimine modified magnetic nanoparticles can remove a lot of coextracts. The range of detection limits and quantification limits was 0.27-0.34 and 0.89-1.13 ng/mL, respectively. Compared with other common methods, the magnetic separation method proposed in this study is much simpler and more effective through both strong cation-π interaction and electrostatic interaction.

Abstract

J. Sep. Sci. 2018, 41, 2056–2063 DOI: https://doi.org/10.1002//jssc.201701098 The cover picture shows the selectivity between polyethyleneimine modified magnetic nanoparticles (PEI‐MNPs) and lignans by strong cation–π interaction. Lignans contain substantial amount of methoxyl and hydroxyl groups, which make them negatively charged. Polyethyleneimine modified magnetic nanoparticles are water‐soluble polycations that comprise a lot of amine functional groups. Due to the surface of MNPs that is full of −NH3+ under the condition about pH 7, MNPs' surface is full of positive charges, leading to a strong electrostatic interaction with lignans. At the same time, the −NH3+ groups on the PEI‐MNPs surface form a strong cation–π interaction with the benzene rings of lignans. The cation–π interaction is potentially stronger than the ammonium carboxylate salt bridges that are formed by PEI‐MNPs with interfering polar chemicals such as citric acid in aqueous media, and the several methoxyl groups on the benzene ring enhance the negative electron cloud density to increase the cation‐π interaction and electrostatic adsorption. By using these interactions, the lignans can be easily and effectively purified.

An open-tubular radially cyclical electric field-flow fractionation technique which realizes the on-line separation of microparticles in a functional annular channel is proposed in this study. The system was set up...