Title Ravnotežna i kinetička istraživanja adsorpcije polifenolnih spojeva na β-glukanu Title (english) Equilibrium and kinetic study of polyphenolic compound adsorption onto β-glucan Author Petra Matić Mentor Lidija Jakobek Barron (mentor)Mentor Šime Ukić (mentor)Committee member Marko Rogošić (predsjednik povjerenstva)Committee member Tomislav Bolanča (član povjerenstva)Committee member Ana Mornar Turk (član povjerenstva)Granter University of Zagreb Defense date and country 2021-06-02, Croatia Scientific / art field, NATURAL SCIENCES Universal decimal classificationUDC ) 54 - Chemistry. Crystallography. Mineralogy Abstract U sklopu doktorskoga rada provedena su ravnotežna istraživanja adsorpcije fenolnih kiselina (galna, p-kumarinska, kafeinska, klorogenska kiselina), flavan-3-ola (procijanidin B1 i B2), dihidrokalkona (floretin, floretin-2-glukozid) te antocijanina (cijanidin-3-glukozid,
cijanidin-3-galaktozid) na prehrambenom vlaknu (β-glukan) pri različitim temperaturama i pH vrijednostima medija. Rezultati su modelirani jednadžbama adsorpcijskih izotermi nelinearnom regresijom. U svrhu kinetičkog istraživanja adsorpcija je ispitana u različitim vremenskim periodima, a podaci su analizirani kinetičkim modelima pseudo-prvog i pseudo-drugog reda. Galna kiselina pokazala je veći adsorpcijski kapacitet od p-kumarinske, kafeinske i klorogenske kiseline što može biti uzrokovano većim brojem OH-skupina na molekuli. Procijanidin B1 i B2 imali su slične adsorpcijske kapacitete. Cijanidin-3-glukozid pokazao je nešto veći adsorpcijski kapacitet od cijanidin-3-galaktozida, a floretin-2-glukozid od floretina, na što je mogla utjecati glikozilacija molekule. Adsorpcija je spontan i egzoterman proces te vjerojatno slijedi kinetiku pseudo-drugog reda s vremenom polureakcije 0,76 do 7,22 h. Snimljeni UV/Vis-spektri potvrdili su postojanje interakcija između polifenola i β-glukana. Postojanje razlika u adsorpcijskim kapacitetima na različitim pH može se objasniti različitim formama polifenola. Za fenolne kiseline važan je udio neprotoniranih/protoniranih skupina, za dihidrokalkone glikozilacija, a za antocijanine njihova različita struktura pri različitom pH. Parametri adsorpcijskih izotermi ukazuju na fizikalnu adsorpciju s H vezama i van der Waalsovim silama između polifenola i β-glukana s negativnom kooperacijom u vezanju na svim temperaturama i pH vrijednostima. Provedena je i adsorpcija polifenola iz ekstrakta mesa i kožice jabuke, a u takvom realnom sustavu koji se sastojao od više različitih polifenola, adsorpcija je bila ovisna o koncentraciji (viša koncentracija, veći adsorpcijski kapacitet) s predloženim vodikovim vezama ili van der Waalsovim silama između polifenola i β-glukana. Provedena istraživanja dala su bolji uvid u interakcije između polifenolnih spojeva i prehrambenih vlakana koje su važne za objašnjenje bioaktivnosti polifenolnih spojeva.
Abstract (english) In this dissertation, equilibrium studies of adsorption of phenolic acids (gallic, p-coumaric, caffeic, chlorogenic acid), flavan-3-ols (procyanidin B1 and B2), dihydrocalcones (floretin, floretin-2-glucoside) and anthocyanins (cyanidin-3-glucoside, cyanidin-3-galactoside) onto dietary fiber (β-glucan) at different temperatures and pH values of the medium are carried out. The results are modeled with adsorption isotherm equations by nonlinear regression. For the purpose of the kinetic research, adsorption was examined in different time periods, and the data were analyzed with kinetic models of pseudo-first and pseudo-second order. Gallic acid showed a higher adsorption capacity than p-coumaric, caffeic and chlorogenic acids which can be caused by a larger number of OH groups on the molecule. Procyanidin B1 and B2 showed similar adsorption capacity. Cyanidin-3-glucoside had a slightly higher adsorption capacity than cyanidin-3-galactoside, and floretin-2-glucoside than floretin, which may have been affected by glycosylation of the molecule. Adsorption was a spontaneous and exothermic process and probably follows pseudo-second order kinetics and the half-life is between 0.76 and 7.22 h. Scanned UV/Vis spectra confirmed the existence of interactions between polyphenols and β-glucan. The existence of differences in adsorption capacities at different pH can be explained by different forms of polyphenols. The proportion of non-protonated and protonated functional groups is important for phenolic acids, glycosylation is important for dihydrocalcones, and structural differences at different pH for anthocyanins. The parameters of the adsorption isotherms indicate physical adsorption with H-bonds and van der Waals forces between polyphenols and β-glucans, with negative cooperation in binding at all temperatures and pH values. Adsorption of polyphenols from the flesh and peel of apples was also performed, and in such a real system consisting of several different polyphenols, adsorption was concentration dependent (higher concentration yielding higher adsorption capacity), with hydrogen bonds or van der Waals forces between polyphenols and β-glucan again indicated. The conducted studies provided a better insight into the interactions between polyphenolic compounds and dietary fiber which are important for explaining the bioactivity of polyphenolic compounds.
Keywords
adsorpcija
kinetika
ravnotežni modeli
polifenoli
β-glukan
Keywords (english)
adsorption
kinetics
equilibrium models
polyphenols
β-glucan
Language croatian URN:NBN urn:nbn:hr:149:721050 Promotion 2021 Project Number: IP-2016-06-6777 Study programme Title: Chemical Engineering and Applied Chemistry - Doctoral course Type of resource Text Extent 109 str. ; 30 cm File origin Born digital Access conditions Open access Terms of use Created on 2023-06-02 10:55:22
