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Preparation of Molecularly Imprinted Adsorbents with Improved Retention Capability of Polyphenols and Their Application in Continuous Separation Processes

Gomes, Catarina P., Dias, Rolando C. S., Costa, Mário Rui P. F. N.
Chromatographia 2019 v.82 no.6 pp. 893-916
adsorbents, adsorption, binding sites, biorefining, carbon dioxide, chestnut shells, chromatography, cork, desorption, ellagic acid, evaporation, hydrophobic bonding, kaempferol, leaf extracts, molecular imprinting, oleuropein, olives, polymers, polyphenols, quercetin, red wines, resins, resveratrol, solubility, solvents, water content
This research explores the use of molecularly imprinted polymers (MIPs) in continuous adsorption processes to target polyphenols present in plant extracts. Different kinds of MIPs were prepared and tested in individual and competitive adsorption/desorption assays. High polyphenol retention was shown to be possible, even when solvents of low water content are used. A lower impact of hydrophobic interactions is observed with MIPs, namely in comparison with commercial synthetic resins, and so, despite the absence of a perfect selectivity, molecular imprinting was congenial in the functionalization and improved binding site accessibility. Moreover, the potential usefulness of the prepared MIPs to improve downstream processing of polyphenols is also demonstrated through their application in chromatographic separation processes. The direct use of plant extracts of high alcoholic content, avoiding the need for solvent change and water addition, the suppression of energetic costs associated to water evaporation and the possibility to work in a wide range of polyphenols solubility are possible advantages of the developed MIP adsorbents in such kinds of biorefining processes. The development of simulation tools to aid the design and optimization of the involved continuous adsorption/desorption is also here addressed. In this work, MIPs were tested with cork and chestnut shell extracts, a supercritical CO₂ olive leaf extract and red wine. Results here obtained show the successful isolation of ellagic acid with cork and chestnut shell extracts, oleuropein with the olive leaf extract and the clear simplification of the red wine extract, enabling the identification/quantification of resveratrol, quercetin, kaempferol and other polyphenols.