Preparation,Application And Mechanism Analysis Of Ligninbased Flavonoids Molecularly Imprinted Polymers

Hibiscus manihot L.is rich in bioflavonoids,and its quality depends to a large extent on the effect of separation and extraction.The best way to achieve efficient separation is to develop new separation functional materials and improve the selectivity of target compounds.To guide the rational picking of flower buds and flowers,the composition and the difference in the content of total flavonoids in flower buds and flowers were analyzed using multi-index high performance liquid chromatography.Aiming at the problems of improving binding capacity,increasing selectivity and analyzing the mass transfer mechanism faced by flavonoids molecular imprinting separation,the methods combined quantum chemical calculations,kinetic simulations and molecular docking with experiments were used to systematically study the selection of functional monomers,the synthesis of molecularly imprinted polymers,the formation of hydrogen bonds and the mechanism of imprinting recognition.The structure and properties of flavonoids and functional monomers,and the interactions of their compounds with different molar ratios were studied theoretically using density functional theory.The results showed that the quality of flower buds was far better than that of flowers.Itaconic acid(IA)was the best functional monomer,followed by acrylamide(AM).The dual polymerization mechanism was used to double cross-link IA,ethylene glycol dimethacrylate(EGDMA)and lignin,and the theoretical models of quercetin molecularly imprinted polymers(QUE-MIP)were constructed,and QUE-MIP was experimentally prepared,optimized,and characterized.Molecular docking and kinetic simulations were performed to study the imprinting interaction of QUE-MIP on quercetin(QUE),hyperoside(HYP),isoquercetin(ISO),quercetin-3'-O-glucopyranoside(ISO-3'),gossypetin-8-O-?-D-glucuronide(HIB)and rutin(RUT).Combining theoretical research with experiments,the formation and imprinting recognition mechanism of QUE-MIP and the main factors affecting the adsorption capacity were discussed.The results showed that the imprinting recognition performance of QUE-MIP was QUE > ISO-3' > ISO > HYP > RUT > HIB.QUEMIP2:4:6:22:9 and QUE-MIP2:8:10:30:9 were the best theoretical models that best match the adsorption process.The proper cross-linking of IA and EGDMA could enhance the imprinting recognition performance.The reversible addition-fragmentation chain transfer(RAFT)polymerization technology was used to construct AM into the theoretical model of lignin grafted polymers,and lignin grafted polymers were experimentally prepared,optimized and characterized.Molecular dynamics simulations were used to predict the effects of glass transition temperature,static mechanical properties,radial distribution function and mean square displacement,as well as combining molecular docking methods,the adsorption sites,the size and formation mechanism of the interaction,the effects of the degree of polymerization and temperature were analyzed.The results showed that RAFT reagents mainly played a role of increasing the number of segments.The proper grafting polymerization of AM and elevating temperature could enhance imprinting interactions.High concentration of adsorption solution could increase the adsorption capacity of QUE-MIP on HIB,ISO-3' and QUE.The adsorption and separation mechanism of itaconic acid cross-linked lignin-based polymers and lignin grafted polymers was studied by adsorption isotherm,kinetics,selectivity and repeatability.The results showed that they conformed to the Langmuir isotherm adsorption model and pseudo-second-order kinetic equation,and had good regeneration ability in five cycles.The two imprinted adsorption materials had maximum adsorption capacities of 19.69 mg/g and 17.28 mg/g,respectively,and total adsorption amounts in the extracts of flower buds were 8.63 mg/g(6 mg/m L)and 8.27 mg/g(10 mg/m L).The new collocation of molecularly imprinted adsorption materials proposed in this paper improves the imprinting recognition performance and the preparation efficiency of molecularly imprinted polymers,and provides new solutions for the industrial preparation and efficient separation of flavonoids molecularly imprinted adsorption materials and the efficient utilization of lignin.