Preparation and adsorption characteristics of rosin-based polymer microspheres for berberine hydrochloride and separation of total alkaloids from coptidis rhizoma

Coptidis rhizoma, the dried rhizome of the plant Coptis, is a source of potentially valuable alkaloids, including berberine hydrochloride (BBH). However, extraction of these compounds is challenging, and existing resins for adsorption-based separation and purification are based on synthetic compounds, which can leach into the product. Therefore, we prepared separation microspheres from a natural compound. The rosin-based polymer microspheres (RBPMs) were synthesized using ethylene glycol maleic rosinate acrylate as a cross-linker and methacrylic acid as a functional monomer. The physical and chemical properties of the RBPMs were characterized by different analytical techniques. The RBPMs had a clean surface, narrow particle size distribution, mesoporous structure, and good thermal stability. BBH was adsorbed onto the RBPMs very efficiently, and the adsorption process was fitted well to the pseudo second-order kinetics, intra-particle diffusion, and Langmuir isotherm model. The thermodynamic parameters indicate that the adsorption process was spontaneous, exothermic, physical, and involved weak chemical bonds. The comprehensive analysis of experimental results suggested that the ion exchange may drive the uptake process of BBH. Dynamic adsorption and desorption tests revealed that the dynamic adsorption capacity of BBH on RBPMs was 612.4 mg/g. Moreover, the separation capability of RBPMs for concentrating coptidis total alkaloids was established using chromatographic column breakthrough experiments, and the content of coptidis total alkaloid increases from 34.2% to over 91.0%. These results suggested that RBPMs are a very promising polymeric adsorption material for concentrating coptidis total alkaloids and purifying BBH from the coptidis rhizoma extracts.