20.500.12556/DKUM-99982 Izolacija in protolitsko ravnotežje punikalagina Isolation and protolytic equilibrium of punicalagin V diplomskem delu smo iz granatnega jabolka izolirali punikalagin in proučili njegovo protolitsko ravnotežje. Razvili analitsko metodo za spremljanje punikalagina v ekstraktu granatnega jabolka s tekočinsko kromatografijo visoke ločljivost. Iz olupkov granatnega jabolka smo z različnimi topili ekstrahirali različne polifenolne spojine. Največ punikalagina smo ekstrahirali z mešanico etanola in vode, nakisane z mravljično kislino. S preparativno kromatografijo smo nato v več korakih izolirali punikalagin in ocenili njegovo kromatografsko čistost, ki je bila 95,66 %. Njegovo istovetnost smo potrdili s primerjavo retencijskega časa z retencijskim časom standarda in analizo NMR. Punikalagin je bil prisoten v anomerih oblikah α in β, pri čemer je bil relativni delež α-PN 61,52 % in β-PN 38,48 %. Razmerje med α in β pa je 1,6:1,0. Nato smo raziskali stabilnost punikalagina s spektroskopijo UV-Vis in pokazali, da je stabilen vsaj eno uro do pH 7,14, medtem ko pri višjih pH pride do ireverzibilne oksidacije spojine. Spremljali smo njegovo ravnotežje s spektroskopijo UV-Vis ter izmerili spektre UV-Vis v območju pH 2–10. Pri največjih spremembah spektrov smo izrisali odvisnost absorbance oziroma valovne dolžine absorpcijskega vrha od pH. Pridobljene krivulje niso imele značilne sigmoidne oblike, značilne za deprotonacijo fenolnih skupin. S prileganjem sigmoidne funkcije določenim odsekom eksperimentalnih podatkov smo kljub temu poskušali ocenili vrednosti pKa skupine punikalagina. Z dokaj visoko zanesljivostjo nam je uspelo določiti le eno vrednost pKa. In this thesis, punicalagin was isolated from pomegranate, and its protolytic equilibrium was investigated. An analytical high-performance liquid chromatography method was developed to monitor punicalagin in the pomegranate extract. Compounds were extracted from pomegranate peels using different solvents. The highest amount of punicalagin was extracted using a mixture of ethanol and water acidified with formic acid. Punicalagin was subsequently isolated in several steps using preparative chromatography, and its chromatographic purity was estimated to be 95.66 %. Its presence was confirmed by comparison with a standard and by NMR analysis. Punicalagin was present as the α- and β-anomers, with relative proportions of 61.52 % α-PN and 38.48 % β-PN, corresponding to an α-PN:β-PN ratio of 1.6:1.0. The stability of punicalagin was then investigated using UV-Vis spectroscopy. It was demonstrated that the compounds were stable for at least one hour at pH 7.14, whereas irreversible oxidation occurred at higher pH values. Its protolytic equilibrium was also monitored by UV-Vis spectroscopy, with spectra recorded over the pH range 2–10. In the spectral regions where the greatest changes were observed, absorbance or the wavelength of the absorption maximum was plotted against pH. The resulting curves did not exhibit a sigmoidal shape characteristic for the deprotonation of phenolic groups. By fitting a sigmoidal function to the segments of experimental data, several pKa values were estimated, while only one pKa value could be determined with sufficient precision. granatno jabolko punikalagin izolacija protolitsko ravnotežje spektroskopija UV Vis pomegranate punicalagin isolation protolytic equilibrium UV-Vis spectroscopy true true false Slovenski jezik Angleški jezik Diplomsko delo/naloga 2026-09-01 12:21:05 2026-09-15 08:04:22 2026-09-16 03:11:25 0000-00-00 00:00:00 2026 0 Maribor 0 0000-00-00 NiDoloceno NiDoloceno NiDoloceno 0000-00-00 0000-00-00 0000-00-00 UN_Mladkovic_Masa_2026.pdf UN_Mladkovic_Masa_2026.pdf 1 26559F3FA286E6D17F734AA5A143A70A d4f19aa554e70188fc0ba18303e6a0dd2c390ece48801d4c6f4452ae21853eb0 30734c58-af89-11f1-873a-00155d0001be https://dk.um.si/Dokument.php?lang=slv&id=212287 Fakulteta za kemijo in kemijsko tehnologijo 0 0 0