Improving imprinting effect by reducing sites embedding: Selective extraction of 1,2,3,4,6-penta-O-galloyl-β-d-glucose from Paeonia lactiflora Pall by hydrophilic molecularly imprinted polymers based on macromonomer and metal ion pivot

Abstract

1,2,3,4,6-Penta-O-galloyl-β-d-glucose (β-PGG) is one of active component of polyphenol tannic acid in the rhizome of radix paeoniae alba, and isolating and purifying β-PGG from crude extract of Paeonia lactiflora Pall is rather challenge work. In this paper, to reduce the embedding of imprinted sites and increase the binding capacity, β-PGG imprinted monoliths were synthesized using a strategy of combination of hydrophilic macromonomer with metal ions as pivot. With a small side chain of oligoethylene glycol, oligo (ethyleneglycol) methyl ether methacrylate (OEG) was chosen as the hydrophilic macromonomer. 4-Vinylpyridine (4-VP) and ethyleneglycol dimethacrylate was used as functional monomer and crosslinker, respectively, and Ni2+ was adopted as metallic pivot. Polymerization parameters, including the ratio of functional monomer/template, ratios of 4-VP to Ni2+, and ratios of OEG to 4-VP on affinity of the resulting molecularly imprinted polymer (MIP) were systematically investigated. The structure and morphology of the obtained monolithic MIP was studied by field emission scanning electron microscopy and multipoint BET measurement. The greatest imprinting factor can be achieved to 68, which gave rise to excellent selectivity of the resulting MIP. When using the MIP as SPE absorbent, the mean recoveries for β-PGG were 74.1% with purity of 98.35%. The results demonstrated that the combination of metal ion pivot with hydrophilic macromonomer is effective approach to the balance of rigidity of imprinting cavities and polymer flexibility and increase the selectivity of the resulting MIP.