doktorska disertacija
Povzetek
V okviru doktorskega dela smo identificirali in kvantificirali karotenoide v ekstraktih
listov v različnih rastnih fazah dveh invazivnih tujerodnih rastlinskih vrst – japonski
dresnik (Fallopia japonica Houtt) in češki dresnik (Fallopia x bohemica). Karotenoidni
profili so bili za obe rastlinski vrsti zelo podobni. Ugotovili smo, da se količina prostih
ksantofilov in karotenov v jesensko obarvanih listih bistveno zmanjša, po drugi strani pa
smo pokazali, da se pojavijo nove ksantofilne spojine – ksantofilni estri maščobnih kislin.
Zeleni listi obeh preučevanih dresnikov predstavljajo bogat in trajnosten naravni vir
bioaktivnih karotenoidov, predvsem β-karotena (69–97 mg/100g s.m.) in prostega luteina
(97–144 mg/100g s.m.), ki bi jih lahko uporabili za pripravo prehranskih dopolnil.
Obstaja pa težava. Ker so karotenoidi izven rastlinske matrice zelo nestabilni in v
prisotnosti povišane temperature, svetlobe, oksidantov, kislin ali kovin hitro razpadejo, je
njihova uporaba omejena. Navdih za reševanje tega problema smo dobili s posnemanjem
naravnih procesov, namreč, estrenje fotosintetskih ksantofilov naj bi v jeseni med drugim
povečalo njihovo kemijsko stabilnost. V ta namen smo razvili prvo okolju prijazno in
ekonomsko upravičljivo sintetsko platformo, kjer smo uporabili zelene, GRAS in
obnovljive reagente ter topila. V β-pinenu kot reakcijskem topilu in pri sobni temperaturi
ter atmosferskem tlaku smo s kombinacijo 5 modelnih ksantofilov in 11 strukturno in
elektronsko različnih kislinskih anhidridov pripravili 55 različnih ksantofilnih estrov.
Pokazali smo, da se estrenje lahko izvede tudi brez topila in z uporabo ekstrakta
odpadnega rastlinskega materiala zelenih listov japonskega dresnika in olupkov avokada,
ki predstavljata bogat obnovljiv vir luteina oziroma anteraksantina. Sintetizirane spojine
smo očistili in jih okarakterizirali na podlagi podatkov pridobljenih s pomočjo
HPLC-PDA-MSn in HRMS. Od 55 spojin jih je bilo 22 prvič uspešno sintetiziranih.
Uspešnost povečanja kemijske stabilnosti ksantofilov preko estrenja smo preverili na 13
različnih luteinskih diestrih, ki smo jih sintetizirali bodisi iz čistega luteina bodisi iz
ekstrakta zelenih listov japonskega dresnika. Vsak luteinski diester smo ločeno izpostavili
posameznemu stresnemu pogoju: povišani temperaturi (60 °C), svetlobi (UV-A),
oksidantu (H2O2) in kislemu okolju. Na podlagi sistematične stabilnostne študije smo prvi
pokazali povezavo med kemijsko stabilnostjo, kemijsko strukturo in okoljem luteinskih
estrov, v katerem se nahajajo. Od vseh pripravljenih estrov so se za najbolj obetavne
izkazali lutein di(2,2-dimetilpropanoat), lutein di(2-metilpropanoat) in lutein di(3-
metilbutanoat), saj so bili, ne glede na izbrani stresni pogoj, 1,4–20-krat bolj stabilni v
primerjavi s prostim luteinom. Ugotovili smo, da lahko matrica rastlinskega ekstrakta
močno vpliva na stabilnost ksantofilov (pozitivno ali negativno), odvisno od stresnega
pogoja in tipa estra. Listi japonskega dresnika torej predstavljajo odpadek, ki na trajnosten
način omogoča pripravo potencialnih izdelkov z visoko dodano vrednostjo – ksantofilnih
estrov s povečano kemijsko stabilnostjo.
Ključne besede
japonski dresnik;Fallopia japonica Houtt;ksantofili;estrenje;ksantofilni estri;stabilnostne študije;kromatografije;HPLC;HPTLC;GC;masna spektrometrija;doktorske disertacije;
Podatki
Jezik: |
Slovenski jezik |
Leto izida: |
2022 |
Tipologija: |
2.08 - Doktorska disertacija |
Organizacija: |
UL FKKT - Fakulteta za kemijo in kemijsko tehnologijo |
Založnik: |
[V. Metličar] |
UDK: |
547.979.8:543.544:543.51(043.3) |
COBISS: |
103075843
|
Št. ogledov: |
311 |
Št. prenosov: |
24 |
Ocena: |
0 (0 glasov) |
Metapodatki: |
|
Ostali podatki
Sekundarni jezik: |
Angleški jezik |
Sekundarni naslov: |
Stabilization of carotenoids isolated from invasive alien plant species and characterization of their preparations |
Sekundarni povzetek: |
Carotenoids in mature (green) and senescing leaves of invasive alien plant species
Japanese (Fallopia japonica Houtt) and Bohemian (Fallopia x bohemica) knotweed were
identified and quantified. Both plants showed similar pigment profiles.The amount of free
xanthophylls and carotenes was significantly lower in senescing leaves in comparison to
green leaves. On the other hand new xanthophyll compounds appeared in senescing
leaves – xanthophyll fatty acid esters. Particularly green leaves of both studied knotweeds
represent a rich and sustainable natural source of bioactive carotenoids, mainly β-carotene
(69–97 mg/100g D.W.) and xanthophyll lutein (97–144 mg/100g D.W.), thus exploitation
of these invaders can be used for the production of high added-value products. However,
due to carotenoids chemical structure, they are very unstable outside of the plant matrix
and they degrade fast in the presence of elevated temperature, light, oxidants, acids and
metals. We found an inspiration to solve this problem in nature itself, where in autumn
xanthophylls are converted into more chemically stable xanthophyll esters. To this end,
we developed the first environmentally friendly and economically viable synthetic
platform, where overall green, renewable, GRAS and recyclable materials were used. The
synthesis was carried out in β-pinene as the reaction solvent and at ambient conditions
(room temperaure, Atmospheric pressure), where 55 different xanthophyll esters
(combining 5 model xanthophylls with 11 structurally and electronically distinct acid
anhydrides) were prepared. We have shown that esterification can be performed also
without use of a solvent and by exploitation of a waste plant material, e.g. extract of green
leaves of Japanese knotweed or avocado peels, which represent rich renewable source of
lutein and anteraxanthin, respectively. The synthesized compounds were purified and
characterized by means of HPLC-PDA-MS and offline HRMS. Out of 55 compounds, 22
were successfully synthesized for the first time. The efficiency of our approach to achieve
higher chemical stability of xanthophylls via esterification was tested on 13 different
lutein diesters, which were synthesized either from pure lutein or from green leaves
extract of Japanese knotweed. Each individual lutein diester was separately examined at
each individual stress conditions: elevated temperature (60 °C), light (UV-A), oxidant
(H2O2) and acidic environment. Based on systematic stability studies, we were first to
identify a relationship between the chemical stability, chemical structure and the
environment by which lutein esters were surrounded. Of all the prepared lutein esters,
lutein di(2,2-dimethylpropanoate), lutein di(2-methylpropanoate) and lutein di(3-
methylbutanoate) proved to be the most stable. They showed to be 1,4–20 times more
stable than free lutein, regardless of the chosen stress condition. Depending on the stress
condition the plant matrix can strongly (positively or negatively) affect the stability of an
individual xanthophyll. The green leaves of Japanese knotweed, therefore, represent a
suitable plant waste material that enables the preparation of potential high value-added
products – xanthophyll esters with increased chemical stability. |
Sekundarne ključne besede: |
Japanese knotweed;carotenoids;xanthophylls;esterification;xantophyll esters;stability;chromatography;mass spectrometry;Karotenoidi;Disertacije;Univerzitetna in visokošolska dela; |
Vrsta dela (COBISS): |
Doktorsko delo/naloga |
Študijski program: |
1000381 |
Komentar na gradivo: |
Univ. v Ljubljani, Fak. za kemijo in kemijsko tehnologijo |
Strani: |
XV f., 120 str. |
ID: |
14900676 |