Search

U poslednjih nekoliko decenija, interes za izučavanjem poznatih i pronalaženjem novih vrsta koje mogu imati značajan antioksidativni potencijal sve više raste. Imajući u vidu da su fenolna jedinjenja poznata kao jako dobri antioksidansi, a da su glavni izvori ovih jedinjenja biljke, konstantno se izučavaju biljne vrste koje potencijalno poseduju visok sadržaj prirodnih antioksidanasa. Familija Rosaceae obuhvata veliki broj biljnih vrsta koje ljudi od davnina koriste u svojoj ishrani, ali su mnoge divlje vrste nedovoljno proučavane, pa je deo ove disertacije baziran na analizi fenolnih jedinjenja u divljim plodovima jabuke, maline i trešnje. U cilju dobijanja maksimalnog prinosa ovih jedinjenja iz biljnog materijala, izvršena je optimizacija metode ekstrakcije fenolnih jedinjenja, i definisani su optimalni uslovi za ekstrakciju, koji obuhvataju pravilan odabir rastvarača (i njegove koncentracije), odnos mase uzorka i zapremine rastvarača, vreme i temperaturu ekstrakcije. U ovako dobijenim ekstraktima, analiziran je ukupan sadržaj fenolnih jedinjenja (ukupnih fenola, fenolnih kiselina, flavonoida i antocijanina), a rezultati su omogućili određivanje optimalnih uslova ekstrakcije ovih jedinjenja u uzorcima primenom softvera Design-Expert® i metodologije odziva površine (eng. Response Surface Methodology). Kvantifikacija pojedinačnih fenolnih jedinjenja u uzorcima dobijenim ekstrakcijom pod optimalnim uslovima izvršena je HPLC metodom, pri čemu su dobijeni rezultati potvrdili da su ovi plodovi bogati sadržajem biološki važnih fenolnih jedinjenja. Dobijene vrednosti koncentracija pojedinačnih fenolnih jedinjenja ukazale su da plodovi ispitivanih samoniklih vrsta familije Rosaceae mogu biti značajan izvor ove grupe jedinjenja u ishrani ljudi. Rezultati i metodologija analize fenolnog sastava ovih plodova, mogu biti od značaja i za buduća ispitivanja i analizu sadržaja fenolnih jedinjenja u plodovima biljaka sličnih karakteristika. Ispitana je i stabilnost i biodostupnost ovih komponenti u organizmu, simulacijom uslova in vitro Ugastrointestinalne digestije. Da bi se rasvetlio antioksidativni potencijal testiranih uzoraka, primenjen je niz metoda koje ispituju njihovu sposobnost da neutrališu štetne slobodno-radikalske vrste. Iako postoji sve veća težnja za nalaženjem i upotrebom prirodnih antioksidanasa, mogućnosti njihove univerzalne primene su često ograničene, pa se pribegava dobijanju antioksidativnih jedinjenja sintetičkim putem. U tom smislu, u ovom radu je izvršena sintetička modifikacija odabranih fenolnih kiselina, sa ciljem nalaženja novih jedinjenja sa boljim biološkim aktivnostima, pre svega antioksidativnom. Na ovaj način su dobijene dve serije jedinjenja, 1,2,4- triazol-3-tioni i 1,3,4-oksadiazoli. Dobijeni rezultati daju doprinos analizi fenolnih jedinjenja u prirodnim proizvodima, njihovoj funkcionalizaciji i primeni In the past several decades, the interest in studying well-known and discovery of new species that may have significant antioxidant potential is constantly growing. Taking into account that phenolic compounds are known as good antioxidants, and that the main sources of these compounds are plants, there is a constant pursuit for plant species potentially possessing a high content of natural antioxidants. The Rosaceae family includes a large number of plant species that humans have used in their diet for a long time, but many wild species are insufficiently studied, therefore part of this PhD thesis is based on the analysis of phenolic compounds in wild apples, raspberries, and cherries (family Rosaceae). In order to obtain the maximum yield of these compounds, optimization of the extraction method of phenolic compounds from plant material was performed, and optimal conditions for extraction, including the appropriate choice of the solvent (and its concentration), the solid to solvent ratio, the time and temperature of the extraction, were defined. The total content of phenolic compounds (total phenols, phenolic acids, flavonoids, and anthocyanins) was analyzed in the obtained extracts, and the obtained results were used in determination of optimal conditions for the extraction of these compounds in the samples using the DesignExpert® software and the response surface methodology. The quantification of individual phenolic compounds in the samples obtained by extraction under optimal conditions was performed by HPLC method and the results confirmed that these fruits are rich in the biologically important phenolic compounds. The obtained concentrations of individual phenolic compounds indicated that the studied wild fruit species of the Rosaceae family could be a significant source of phenolic compounds in human nutrition. The results and methodology of analyzing the phenolic composition of these fruits can be of importance for future research and analysis of phenolic compounds content in fruit or plants with similar characteristics. Furthermore, the stability and bioaccessibility of these components in the organism were examined by the simulation of the in vitro gastrointestinal digestion conditions. In order to clarify the Iantioxidant potential of the tested samples, a number of methods for determination of the ability of obtained extracts to neutralize harmful free-radical species have been applied. Although there is a growing tendency to find and use natural antioxidants, the possibilities of their universal application are often limited, therefore antioxidant compounds are often synthetically obtained. The synthetic modification of selected phenolic acids was carried out with the aim of finding a new series of compounds with better biological activities, mainly antioxidant activity. Two series of novel compounds were synthesized, 1,2,4-triazol-3-thiones and 1,3,4-oxadiazoles. The obtained results in this PhD thesis contribute to the analysis of phenolic compounds in natural products, their functionalization, and application.

Eight 1,3,4-oxadiazole derivatives containing phenolic acid moieties (7a–h) and eight of their diacylhydrazine precursors (6a–h) were synthesized, characterized using spectroscopic methods and examined by scavenging of stable DPPH (2,2-diphenyl-1-picrylhydrazyl) radicals. The most potent phenolic 1,3,4-oxadiazoles showed better DPPH scavenging activity in comparison with their corresponding diacylhydrazine precursors as a result of participation of both aromatic rings and a 1,3,4-oxadiazole moiety in resonance stabilization of the formed phenoxyl radical. Four diacylhydrazines (6d, 6e, 6g, and 6h) and four 1,3,4-oxadiazoles (7d, 7e, 7g and 7h) with the best DPPH scavenging activity, were chosen for further evaluation of their antioxidant potential through various assays. The investigated compounds exerted pronounced ABTS radical scavenging capacity, moderate to good H2O2 scavenging properties and strong ferric ion reducing capacity. Further in vitro evaluation of the antioxidant properties of the most active compounds demonstrated their protective effects in normal lung fibroblasts MRC-5 against hydrogen peroxide induced oxidative stress. Diacylhydrazine 6h increased two times the activity of glutathione peroxidase in treated cells in comparison with a control sample and did not affect the superoxide dismutase activity.

A simple field trial was performed to investigate the influence of less successful miscanthus culture establishment due to scarce planting on the yield of aboveground biomass. The trial was carried out on highly productive soil of non-carbonate chernozem type. Two months old miscanthus sprouting rhizomes with 1-2 developed stems were planted. The experiment included three levels of planting density: 0.50, 0.65 and 1.00 sprouting rhizomes/m2. At the lowest planting density (0.50), the average yield of 4-8 years old plantation, which is the stage with the highest aboveground biomass yield, amounted to 13.5±2.9 t dry matter (d.m.)/ha, while at the planting density of 1.00, the achieved yield was 21.2±4.5 t d.m./ha. Our results show that, at the recommended planting density of 15000 rhizomes/ha, on a highly productive soil, even with low survival of planted seedlings (> 43 %), satisfying yields of aboveground miscanthus biomass may be obtained. Cilj istraživanja je da se jednostavnim ogledom u poljskim uslovima ustanovi uticaj nižih nivoa uspešnosti zasnivanja miskantusa kroz proređenu sadnju (presađivanje) biljčica miskantusa na obrazovanje prinosa nadzemne biomase. Poljski ogled je zasnovan na visoko-produktivnom zemljištu tipa izluženi černozem. Sađeni su busenovi miskantusa starosti 2 meseca, sa 1-2 razvijena stabla. Ogled je obuhvatio 3 gustine sadnje: 0,50; 0,65 i 1,00 busenova miskantusa po m2. Faza zasnivanja useva trajala je 3 godine. Pri najnižoj gustini sadnje (0,50) prosečan prinos useva od 4-8 godine gajenja, kada se dostižu maksimumi prinosa nadzemne biomase, iznosio je 13,5±2,9 tona suve materije (s.m.)/ha, naspram 21,2±4,5 tona s.m./ha pri gustini sadnje 1,00. Rezultatipokazaju da se kod preporučene gustine sadnje rizoma miskantusa od 15000 rizoma/ha, na visoko produktivnom zemljištu, u povoljnim agroekološkim uslovima i pri relativno niskom prijemu (>43%) mogu dobiti zadovoljavajući prinosi nadzemne biomase miskantusa.

M20 M21