title: Homogeneous and heterogeneous methods for laccase-mediated functionalization of chitosan by tannic acid and quercetin.
abstract: Homogeneous and heterogeneous methods for functionalization of chitosan with quercetin or tannic acid using laccase from Trametes versicolor is presented, yielding a bio-based product with synergistic antioxidant and antimicrobial properties. HPLC-SEC analysis and cyclic voltammetry kinetic studies showed that laccase catalyzes the oxidation of quercetin to electrophilic o-quinones, which undergo to an oligomer/polymer-forming structures. On the other hand, tannic acid was converted into gallic acid, its dimers, partially gallic acid esterified glucose and glucose, when exposed to laccases. ATR-FTIR spectroscopy provided evidence that quercetin o-quinones undergo coupling reactions with amino groups of chitosan via Schiff-base and Michael addition mechanisms under heterogeneous method, while oxidized tannic acid cross-linked with chitosan by hydrogen and electrostatic interactions under both methods. All polyphenols functionalized chitosans showed greatly improved ABTS(+) cation radicals scavenging capacity, compared with the untreated chitosan, while antimicrobial activities significantly depended on the mode of functionalization and type of microorganism.
authors.affiliation: Institute for Engineering Materials and Design, University of Maribor, Smetanova ul. 17, SI-2000 Maribor, Slovenia.
authors.forename: Mojca
authors.initials: M
authors.lastname: Božič
authors.forename: Selestina
authors.initials: S
authors.lastname: Gorgieva
authors.forename: Vanja
authors.initials: V
authors.lastname: Kokol
mesh_terms: D048271:Chitosan / Q000737:chemistry*; D002850:Chromatography, Gel; D002851:Chromatography, High Pressure Liquid; D042845:Laccase / Q000737:chemistry*; D011794:Quercetin / Q000737:chemistry*; D017550:Spectroscopy, Fourier Transform Infrared; D013634:Tannins / Q000737:chemistry*
chemical_list: D013634:Tannins; D048271:Chitosan; D011794:Quercetin; D042845:Laccase