Surface Molecularly Imprinted Cellulose-Synthetic Hybrid Particles Prepared via ATRP for Enrichment of Flavonoids in Olive Leaf

Surface molecularly imprinted cellulose-synthetic hybrid particles are prepared via atom transfer radical polymerization (ATRP). The two-step process involves the immobilization of α-bromoisobutyryl bromide in the pristine microcrystalline cellulose, to generate ATRP macroinitiator particles, and then the creation of a crosslinked-imprinted shell in the particles surface considering ATRP of 4-vinylpyridine (4VP) and ethylene glycoldimethacrylate (EGDMA) with quercetin as imprinting template. Among the polymerization recipes tested, a system with ethanol as solvent preserves a final size of the hybrid particles suitable for application as adsorbent, while also incorporating the 4VP/EGDMA co-monomers. Testing of imprinted/non-imprinted particles for sorption/desorption of standard phenolic compounds shows the modification of the surface of the pristine cellulose and also the achievement of molecular imprinting (imprinting factor ≈2.6). Particles are used for the enrichment of flavonoids in olive leaf extracts and the special features of the developed molecularly imprinted adsorbents are again highlighted with this complex mixture of phenolic compounds. It is shown that production of fractions rich in luteolin-7-O-glucoside, apigenin-7-O-glucoside, or quercetin, among other flavonoids is possible (estimated enrichment factors up to 4). These results point up for the usefulness of natural-synthetic materials with processes to get high-added value compounds in the framework of circular bio-economy.