doctoral dissertation
Milena Ivanović (Author), Mitja Kolar (Mentor), Maša Islamčević Razboršek (Co-mentor)

Abstract

The objective of this doctoral dissertation was to develop different analytical approaches for the extraction, separation, identification and quantitative determination of various phenolic compounds from different plants and their products. This dissertation is divided into the following four major segments, which, to some extent, can stand alone, but when it comes to the research, they are mutually very related: - Segment 1: Short-term (up to 24 h) and long-term (up to 1 month) stability studies of trans-caffeic acid (trans-CA) and trans-ferulic acid (trans-FA) dissolved in two organic solvents (methanol and tetrahydrofuran) and exposed to a range of storage conditions (temperature, organic solvents used, influence of daylight and UV irradiation) were performed for the first time. Gas chromatography with mass spectrometry (GC-MS) was used to study the degradation of the samples and structural identification of the degradation products. - Segment 2: The research within this segment focused on the optimization of a simple, fast and quantitative extraction method for the isolation of phenolic acids (PAs) from Slovenian red wine samples. Different extraction techniques were tested, and solid phase extraction (SPE) using HLB cartridges was selected as the optimal technique. For the identification and quantification of extracted analytes, the GC-MS method was optimized and validated. Different statistical and chemometrical tools were applied, and the wines were classified according to the Slovenian wine-growing regions and vine varieties. - Segment 3: The main goal within this research segment was the development of an ultrasound-assisted extraction (UAE) method for the isolation of different polyphenol classes from coriander fruits. Additionally, for the isolation of total PAs (free and bound), two analytical steps were applied: UAE alkaline hydrolysis and clean-up using SPE HLB cartridges. The response surface methodology (RSM) combined with a Box-Behnken experimental design (BBD) were used for the optimization of the alkaline hydrolysis and for increasing the extraction yields of the PAs. In this way, most influencing factors (temperature, sonication time and NaOH concentration) were studied as independent variables. Extracted PAs were determined using the previously optimized GC-MS method. - Segment 4: The main goal of this segment of the dissertation was to show the application of deep eutectic solvents (DESs) as a ‘green’ alternative to the conventional organic solvents for the isolation of phenolic compounds from plants such as Aronia melanocarpa (dried chokeberry) and Olea europaea (olive leaves). Different extraction techniques and instrumental methods were applied for the determination of phenolic profiles. Phenols from chokeberries were obtained through UAE. Furthermore, for the simultaneous identification and quantitative determination of 21 different phenolic compounds from Aronia melanocarpa, the HPLC-UV method was optimized and validated. On the other hand, microwave-assisted extraction (MAE) was used to improve the extraction yields of phenolic compounds from olive leave samples, which were subsequently determined by using validated HPLC-DAD-ESI-TOF-MS method.

Keywords

phenolic compounds;phenolic acids;extraction;method optimization;deep eutectic solvents;plant material;

Data

Language: English
Year of publishing:
Typology: 2.08 - Doctoral Dissertation
Organization: UM FKKT - Faculty of Chemistry and Chemical Engineering
Publisher: [M. Ivanović]
UDC: 664.1.033:665.662.3(043.3)
COBISS: 21337366 Link will open in a new window
Views: 1391
Downloads: 125
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Other data

Secondary language: Slovenian
Secondary title: Razvoj analiznih metod za sočasno identifikacijo in določevanje fenolnih spojin
Secondary abstract: Cilj doktorske disertacije je bil razvoj različnih analitskih pristopov za ekstrakcijo, ločevanje, identifikacijo in kvantitativno določanje različnih fenolnih spojin iz različnih rastlin in njihovih produktov. Raziskovalna vsebina disertacije je razdeljena na štiri glavne segmente, ki so v določeni meri samostojni, vendar so raziskave medsebojno tesno povezane. - Segment 1: ta segment je zajemal kratkoročne (do 24 h) in dolgoročne (do 1 meseca) študije stabilnosti trans-kavne kisline in trans-ferulne kisline, ki so bile izvedene pod različnimi pogoji hranjenja: temperatura, uporabljena organska topila, vpliv dnevne svetlobe in UV-sevanja. Prvič je bila uporabljena plinska kromatografija v povezavi z masno spektrometrijo (GC-MS) za študij degradacije vzorcev in strukturne identifikacije razgradnih produktov. - Segment 2: raziskave v tem segmentu je bil poudarek na optimizaciji enostavne, hitre in kvantitativne metode za ekstrakcijo in izolacijo fenolnih kislin iz vzorcev slovenskih rdečih vin. Testirane so bile različne tehnike ekstrakcije, kot optimalna pa je bila izbrana ekstrakcija na trdno fazo (SPE) ob uporabi HLB kolonic. Za identifikacijo in kvantifikacijo ekstrahiranih analitov je bila optimizirana in validira GC-MS metoda. Uporabili smo različna statistična in kemometrična orodja, da smo lahko vina razvrstili glede na slovenska vinorodna območja in sorte vinske trte. - Segment 3: glavni cilj tega raziskovalnega segmenta je bil razvoj ultrazvočne metode (UAE) za izolacijo različnih polifenolov iz koriandra. Poleg tega sta bila za izolacijo skupnih fenolnih kislin (prostih in vezanih) uporabljena dva analitska pristopa: alkalna hidroliza z UAE in čiščenje ob uporabi SPE in HLB kolonic. Optimizacijo alkalne hidrolize in povečanje izkoristkov ekstrakcije fenolnih kislin iz koriandra smo dosegli z metodologijo odzivne površine (RSM) z zasnovo Box-Behnken-ovega (BBD) eksperimentalnega načrta. Na ta način so bili kot neodvisne spremenljivke preučevani najbolj vplivni parametri (temperatura, ultrazvok in koncentracija NaOH). Ekstrahirane fenolne kisline so bile določene z uporabo predhodno optimizirane GC-MS metode. - Segment 4: v tem delu disertacije je predstavljena uporaba globokih eutektičnih topil (DES), kot "zelena" alternativa običajnim organskim topilom, za izolacijo fenolnih spojin iz rastlin, kot so Aronia melanocarpa (posušena aronija) in Olea Europaea (oljčni listi). Za določitev fenolnih profilov smo uporabili različne ekstrakcijske tehnike in instrumentalne metode. Fenoli iz posušene aronije so bili ekstrahirani s pomočjo UAE. Za sočasno identifikacijo in kvantitativno določitev enaindvajsetih različnih fenolnih spojin iz aronije je bila optimizirana in validirana HPLC-UV metoda. Za ekstrakcijo fenolnih spojin iz oljčnih listov pa je bila uporabljena ekstrakcija s pomočjo mikrovalov (MAE), spojine pa so določene z uporabo validirane HPLC-DAD-ESI-TOF-MS metode.
Secondary keywords: fenolne spojine;fenolne kisline;optimizacija metod;globoko eutektična topila;rastlinski materiali;doktorske disertacije;
URN: URN:SI:UM:
Type (COBISS): Doctoral dissertation
Thesis comment: Univ. v Mariboru, Fak. za kemijo in kemijsko tehnologijo
Pages: XVIII, 149 str.
ID: 10860547