Green synthesis and evaluation of isoquercitrin imprinted polymers for class-selective separation and purification of flavonol glycosides

Abstract

A method for solid-phase extraction (SPE) of isoquercitrin (ISO) from natural plant extracts was proposed based on molecularly imprinted polymers (MIPs). The efforts in the present work aim at the emphasis on the topic of “green” chemistry, i.e., the use of green solvent and ionic liquid with a high percentage (63.2–69.3%) in the total volume of porogenic solvent. For the preparation of ISO-MIP monoliths, 4-vinylpyridine was used as the functional monomer, and ethylene glycol dimethacrylate was used as the cross-linking monomer, using a mixture of 1-butyl-3-methylimidazoliumtetrafluoroborate (ionic liquid)-N′N-dimethylformamide (DMF)-dimethyl sulfoxide as a porogen. It was found that the type of functional monomer, the ratio of template to functional monomer, the crosslinking degree, and the level of DMF, and the composition of the mobile phase greatly affected the retention of the template and performance of molecular recognition. The optimal MIPs were used as solid-phase extraction (SPE) sorbents for purification of ISO, hyperoside, and astragalin and a SPE protocol was optimised for the type of loading solvent, amount of MIPs, and washing and elution solvents. It was found that the most suitable solvents for loading, washing and elution steps were methanol–water (70 : 30, v/v), methanol–water (20 : 80, v/v) and acetonitrile–water (30 : 70, v/v), respectively. The highest recovery rate of ISO, hyperoside, and astragalin was 87.78%, 93.26% and 83.25%, respectively, from the crude extract of cotton flowers.