doctoral dissertation
Nika Kučuk (Author), Maja Leitgeb (Mentor), Mateja Primožič (Co-mentor)

Abstract

Doktorska disertacija je razdeljena na štiri dele, v katerih sta obravnavana študija biološke aktivnosti ekstraktov olupkov manga (MPE) ter optimiranje sinteznih metod transportnih sistemov (alginatne kroglice, liposomi in micelarne membrane mikrobnega izvora), vključno z njihovo funkcionalizacijo z MPE za različne terapevtske aplikacije (in vitro). V prvem delu smo s pomočjo različnih ekstrakcijskih metod iz svežih in suhih olupkov manga pridobili MPE z visoko vsebnostjo totalnih fenolov, proantocianidinov, posameznih fenolnih spojin, proteinov in nekaterih encimov v aktivnih oblikah ter z visoko antioksidativno aktivnostjo. Nadalje smo potrdili protibakterijske lastnosti testiranih MPE na rast Gram-negativnih (Escherichia coli, Pseudomonas aeruginosa) ter Gram-pozitivnih bakterij (Bacillus cereus, Staphylococcus aureus). Z uporabo nizkocenovnega postopka sušenja olupkov manga na zraku smo ohranili biološko aktivnost MPE. Na vsebnost bioaktivnih spojin in biološko aktivnost pa sta vplivala tudi uporabljena ekstrakcijska metoda in topilo. Ultrazvočni etanolni MPE iz suhih olupkov je zagotovil dobro protibakterijsko in antioksidativno delovanje, zato smo ga v nadaljevanju vgradili v različne transportne sisteme. V drugem delu smo MPE enkapsulirali v alginatne kroglice, proizvedene z metodo ionotropske gelacije. Sintetizirani napredni biološko aktivni sistem izkazuje dobro termično stabilnost s temperaturo degradacije nad 270 °C. Prav tako ni bilo prisotnih razpok na površini sintetiziranih liofiliziranih alginatnih kroglic. Alginatne kroglice so se izkazale kot odličen transportni sistem za enkapsuliran MPE zaradi stabilnosti pri kislih želodčnih pogojih in posledično doseganje tarčnega mesta (črevesje), kjer smo dosegli postopno sproščanje MPE, kar pomembno vpliva na uspešno absorpcijo v telesu. S protibakterijsko študijo smo dokazali pomemben inhibitorni učinek alginatnih kroglic z MPE na rast patogenih črevesnih bakterij E. coli in S. aureus. V tretjem delu smo optimirali sintezo liposomov za uspešno enkapsulacijo MPE. Za formulacijo liposomov smo uporabili metodo hidracije tankega lipidnega filma z dodatkom 5 mm steklenih kroglic in 24-h stresanjem. Zelo stabilno in monodisperzno formulacijo liposomov z velikostjo delcev <300 nm smo dosegli z uporabo polarnega organskega topila etanola, z uporabo nepolarnih topil pa so najboljšo stabilnost izkazovali liposomi, proizvedeni s kloroformom. Uspešno smo enkapsulirali MPE v liposome in potrdili profil enakomernega sproščanja MPE, vključno z inhibitorno aktivnostjo na rast E. coli in S. aureus. Sintetizirani liposomi z enkapsuliranim MPE se med postopkom liofilizacije niso degradirali, prav tako so bili termično stabilni in ni bilo zaznati signifikantnih kemijskih interakcij med enkapsulirano bioaktivno spojino ter lipidi fosfolipidnega dvosloja. V četrtem delu smo optimirali gojenje terapevtskih gob Ganoderma lucidum in Pleurotus ostreatus s submerzno kultivacijo za doseganje najvišjega prirasta in posledično najintenzivnejše tvorbe micelarnih membran s sposobnostjo visoke absorpcije vode. Sestava in pH rastnega medija sta imela ključen vpliv na tvorbo membran ter njihove karakteristike. Najustreznejši rastni pogoji so bili zagotovljeni pri bazičnem pH v mediju, ki je vseboval sladni ekstrakt za G. lucidum, in v mediju z dodatkom glukoze za P. ostreatus. Zaradi hidrofilne spodnje površine micelarnih membran so te izkazovale visoko sposobnost absorpcije vode, in sicer več kot 600 % za P. ostreatus in do 500 % za G. lucidum. Potrdili smo prisotnost širokega spektra funkcionalnih skupin, termično stabilnost s temperaturo degradacije nad 260 °C ter vlaknasto in porozno strukturo nastalih micelarnih membran. Micelarne membrane obeh gob smo nadalje uspešno funkcionalizirali z MPE ter dosegli enakomeren in postopen profil sproščanja MPE, vključno z uspešnim protibakterijskim delovanjem funkcionaliziranih membran na rast E. coli in S. aureus.

Keywords

mango;ekstrakcija;polifenolne spojine;protibakterijska aktivnost;transportni sistemi;alginatne kroglice;liposomi;micelarne membrane;funkcionalizacija;enkapsulacija;vgrajevanje;in vitro sproščanje;karakterizacija;doktorske diseratcije;

Data

Language: Slovenian
Year of publishing:
Typology: 2.08 - Doctoral Dissertation
Organization: UM FKKT - Faculty of Chemistry and Chemical Engineering
Publisher: [N. Kučuk]
UDC: [66.061.3:634.441]:[604.4:615.33](043.3)
COBISS: 209878019 Link will open in a new window
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Other data

Secondary language: English
Secondary title: Advanced biologically active delivery systems of mango extracts (Mangifera indica) for therapeutic applications in vitro
Secondary abstract: The dissertation is divided into four parts dealing with the study of the biological activity of mango peel extracts (MPEs) and the optimization of the synthesis methods of delivery systems (alginate beads, liposomes, and micellar membranes of microbial origin), including their functionalization with MPE for various therapeutic applications (in vitro). In the first part, MPEs with a high content of total phenols, proanthocyanidins, individual phenolic compounds, proteins, certain enzymes in active form, and high antioxidant activity were obtained from fresh and dry mango peels using various extraction methods. In addition, the antibacterial properties of the tested MPEs on the growth of Gram-negative (Escherichia coli, Pseudomonas aeruginosa) and Gram-positive bacteria (Bacillus cereus, Staphylococcus aureus) were confirmed. The biological activity of the MPE could be maintained by a cost-effective method of air-drying mango peels. The extraction method and the solvent used influenced the content of bioactive compounds and their biological activity. The ethanolic ultrasonic MPE from dried peels showed good antibacterial and antioxidant activity and was subsequently incorporated into various delivery systems. In the second part, the MPE was encapsulated in alginate beads prepared by ionotropic gelation. The synthesized advanced bioactive system showed good thermal stability with a decomposition temperature above 270 °C. Moreover, no cracks were observed on the surface of the synthesized freeze-dried alginate beads. The alginate beads proved to be an excellent delivery system for encapsulated MPE due to their stability under acidic gastric conditions. Consequently, they reached the target site (intestine), where a gradual release of MPE was achieved, which significantly impacts the successful absorption in the body. An antibacterial study showed a significant inhibitory effect of alginate beads with MPE on the growth of the pathogenic intestinal bacteria E. coli and S. aureus. In the third part, the synthesis of liposomes was optimized for the successful encapsulation of MPE. The thin lipid film hydration method with the addition of 5 mm glass beads and shaking for 24 hours was used to formulate the liposomes. A highly stable and monodisperse formulation of liposomes with a particle size <300 nm was achieved with the polar organic solvent ethanol, while liposomes prepared with chloroform showed the best stability among the non-polar solvents. Successful encapsulation of MPE in liposomes and a sustained release profile of MPE were achieved, including an inhibitory effect on E. coli and S. aureus growth. The synthesized MPE-encapsulated liposomes did not degrade upon freeze-drying and were thermally stable. In the fourth part, the cultivation of the medicinal mushrooms Ganoderma lucidum and Pleurotus ostreatus was optimized by submerged cultivation to achieve the highest growth and, thus, the most intensive formation of micellar membranes with a high water absorption capacity. The composition and pH of the growth medium had a decisive influence on membrane formation and its characteristics. The most suitable growth conditions were provided at alkaline pH in the medium with malt extract for G. lucidum and in the medium with added glucose for P. ostreatus. Due to the hydrophilic underside of the micellar membranes, they showed a high water uptake capacity of more than 600% for P. ostreatus and up to 500% for G. lucidum. The presence of a broad spectrum of functional groups, the thermal stability with decomposition temperatures above 260 °C, and the fibrous and porous structure of the resulting micellar membranes were confirmed. The micellar membranes of both mushrooms were further successfully functionalized with MPE, and a uniform and gradual release profile of MPE was achieved, including a successful antimicrobial activity of the functionalized membranes on the growth of E. coli and S. aureus.
Secondary keywords: mango;extraction;polyphenolic compounds;antibacterial;delivery systems;alginate beads;liposomes;micellar membranes;functionalization;encapsulation;incorporation;in vitro release;characterization;
Type (COBISS): Doctoral dissertation
Thesis comment: Univ. v Mariboru, Fak. za kemijo in kemijsko tehnologijo
Pages: XVII, 167 str.
ID: 23740093