The Synthesis of 2´, 3' - Dideoxynucleozides

U radu je ostvarena višefazna transformacija D-ksiloze u pogodno funkcionalizovane derivate koji su kuplovanjem sa siliranim timinom selektivno dali nukleozide sa beta-konfiguracijom na anomernom centru. Takođe, u cilju sinteze nukleozida L-serije, ispitana je mogućnost izomerizacije nekih derivata D-šečera u odgovarajuće L-stereoizomere.Muitistep transformation of D-xylose to suitabte functional derivatives were achieved. Coupling of these derivatives with silylated thymine gave the nucleosides with beta-configuration on anomeric centre. In order to synthesis nucleosides of L-series, the possibility for isomerization of some kinds D-sugar derivatives in corresponding L-stereisomeric compounds, were investigatet, too

The Synthesis of 2´, 3' - Dideoxynucleozides

U radu je ostvarena višefazna transformacija D-ksiloze u pogodno funkcionalizovane derivate koji su kuplovanjem sa siliranim timinom selektivno dali nukleozide sa beta-konfiguracijom na anomernom centru. Takođe, u cilju sinteze nukleozida L-serije, ispitana je mogućnost izomerizacije nekih derivata D-šečera u odgovarajuće L-stereoizomere.Muitistep transformation of D-xylose to suitabte functional derivatives were achieved. Coupling of these derivatives with silylated thymine gave the nucleosides with beta-configuration on anomeric centre. In order to synthesis nucleosides of L-series, the possibility for isomerization of some kinds D-sugar derivatives in corresponding L-stereisomeric compounds, were investigatet, too

Utilization of tomato waste as a source of polyphenolic antioxidants

This study is concerned with the effects of two extraction procedures (using ultrasonic bath and high performance homogenizer) on the extraction efficiency of polyphenolics present in the tomato waste. The isolation of flavonoid fraction of obtained extracts was performed by solid-phase extraction. The antioxidant activity of flavonoid fractions was determined using different spectrophotometric tests, including reducing power and 2,2- diphenyl-1-picrylhydrazyl (DPPH) free radical scavenging assays. The content of total polyphenolics and flavonoids in extract obtained employing homogenizer (E2) was higher than in the extract obtained employing ultrasonic bath (E1), and it was 14.33 mg/g and 7.70 mg/g, respectively. The flavonoid fraction (EF2) of extract E2 showed higher antioxidant activity than flavonoid fraction (EF1) of extract E1. The DPPH free radical scavenging activity of fractions EF1 and EF2, expressed as EC50 value, were 0.78 mg/ml and 0.45 mg/ml, respectively. The obtained results show that tomato wastes can be used as an easily accessible source of antioxidant polyphenolics

Kinetic behaviour of DPPH radical scavenging activity of tomato waste extracts

The kinetic behaviour of tomato waste extracts (obtained from six genotypes) and standard antioxidant compounds (ascorbic and caffeic acid) were investigated using 2,2-diphenyl-1-picrylhydrazyl radical test. Based on the time needed for the reaction to reach steady state, the investigated extracts show very slow (steady state ≥ 180 min) antiradical behaviour, ascorbic acid act as rapid antioxidant (steady state < 5min) while caffeic acid is rapidintermediate antioxidant (5 min < steady state < 20 min). The efficient concentrations at different kinetic times EC50,t were determined for all extracts, ascorbic and caffeic acid. EC50,t was used as a parameter to screen and compare antiradical activities of food extracts with slow kinetic action. Irrespective of the time considered, the comparison of the EC50,t for extracts showed that the DPPH radicals scavenging activity of extracts decreased in the order of O2 > Knjaz > Bačka > Saint Pierre > Rutgers > Novosadski niski. Tomato waste extracts showed very slow kinetic action, which is probably result of the different kinetic bevaviour of phenolic compounds, present in tomato waste, as well as other antioxidants (vitamins, carotenoids etc)

Hplc analysis of phenolic acids in mountain germander (Teucrium montanum L) extracts

The methanol, petroleum ether, chloroform, ethyl acetate, 1-butanol and water extracts were obtained by extraction of mountain germander (Teucrium montanum L). The total phenolic content in extracts was measured by Folin-Ciocalteu method. The 1-butanol extract had the highest phenolic content (296.00 mg/g). High performance liquid chromatography (HPLC) was employed to define qualitative and quantitative content of phenolic acids in mountain germander extracts. The largest number of phenolic acids were determined in ethyl acetate and 1-butanol extracts, while these acids were not present in petroleum ether extract. The highest content of phenolic acids (28.619 mg/g) had ethyl acetate extract and gentisic acid (14.432 mg/g) was its major component. Despite of a large number of phenolic acids in 1-butanol extract their content was only 3.740 mg/g

Chemical composition and antioxidant activity of two strawberry cultivars

The macro- and micro-chemical composition, as well as antioxidant activity of two strawberry cultivars, Marmolada and Clery, were studied. Results showed a noticeable difference in the sugar, protein and pectin contents. Clery had 6.92% and Marmolada 4.93% of total sugar. Also, protein and pectin contents were higher in the Clery cultivar. No significant difference was observed in acidity, as well as in ash and cellulose content. Marmolada had a higher content of total phenolics and flavonoids (228.04 mg GAE /100 g FW and 136.01 mg RE/100 g FW, respectively ). The anthocyanins content in Marmolada (32.0 mg CGE/100 g FW) was slightly lower than in Clery (36.0 mg CGE/100 g FW). The antioxidant activity was evaluated spectrophotometrically, using 2,2-diphenyl- 1-picrylhydrazyl (DPPH) radical scavenging activity assay. The DPPH free radical scavenging activity, expressed as EC50 value, of Marmolada (0.77 mg/ml )was higher than of Clery (0.83 mg/ml). There was a significant positive correlation (R2>0.90) between the concentration of phenolics/flavonoids/anthocyanins and DPPH radical scavenging activity of both strawberry cultivars. These results also showed that the antioxidant value of 100 g FW Marmolada and Clery is equivalent to 237.91 mg and 219.01 mg of vitamin C, respectively

Influence of different combinations of wall materials on the encapsulation of butternut squash waste extract

The aim of this study was to evaluate the effect of different amounts of carrier agents (maltodextrin, inulin and pea protein) on the content of phenolics and carotenoids from butternut squash waste extract in encapsulates obtained by freeze-drying technique. Using Simplex-Centroid experimental design and response surface methodology (RSM), the highest content of both phenolics and carotenoids in the encapsulate was determined for a wall blend ratio 53.9 % pea protein, 46.1 % maltodextrin and 0% inulin

Encapsulation and Degradation Kinetics of Bioactive Compounds from Sweet Potato Peel During Storage

Pozadina istraživanja. Svrha je ovog istraživanja bila procijeniti mogućnost korištenja ljuske slatkog krumpira kao izvora bioaktivnih spojeva. Ispitan je utjecaj otapala (acetona i smjese acetona i etanola) na učinkovitost ekstrakcije ukupnih karotenoida i polifenola iz gomolja, mesa i ljuske slatkog krumpira. Ekstrakt ljuske slatkog krumpira isticao se dobrom antioksidativnom aktivnošću, pa je odabran za inkapsulaciju pomoću sušenja raspršivanjem i liofilizacije. Eksperimentalni pristup. Inkapsulacija je učinkovita metoda poboljšavanja stabilnosti fitokemikalija zadržavanjem aktivne komponente unutar nosača. U ovom su radu tehnike sušenja raspršivanjem i liofilizacijom upotrijebljene za poboljšanje stabilnosti bioaktivnih spojeva (karotenoida i polifenola), uz korištenje proteina sirutke kao nosača. Glavne prednosti primjenjenih metoda u odnosu na ostale tehnike inkapsulacije su jednostavnost, kontinuitet, efikasnost, dostupnost i primjenjivost. Rezultati i zaključci. Na osnovi rezultata fizičko-kemijske karakterizacije može se zaključiti da su tehnikom sušenja raspršivanjem dobivene čestice inkapsulata manjih dimenzija, s boljim svojstvima protočnosti i boljom učinkovitosti inkapsulacije karotenoida. Retencija inkapsuliranih i neinkapsuliranih bioaktivnih spojeva praćena je tijekom skladištenja na dnevnoj svjetlosti i u mraku. Uvjeti skladištenja utjecali su na retenciju karotenoida, dok je veća brzina degradacije karotenoida zamijećena u svim uzorcima skladištenim na dnevnoj svjetlosti. Fenolni spojevi imali su veću retenciju u svim ispitanim uzorcima. Kinetički parametri degradacije sugeriraju da je dulji rok trajanja inkapsuliranog ekstrakta postignut sušenjem raspršivanjem, te da je ta metoda dobra za stabilizaciju ispitanih bioaktivnih spojeva. Novina i znanstveni doprinos: Ovo istraživanje pokazuje da sušenje raspršivanjem i upotreba ljuske slatkog krumpira imaju velik potencijal za razvoj funkcionalnih dodataka hrani s poboljšanim hranjivim i bioakivnim svojstvima, te ljepšom bojom proizvoda.Research background. The aim of this work is to evaluate utilization of sweet potato peel as a source of bioactive compounds. The effect of solvents (acetone and acetone/ethanol mixture) on the extraction efficiency of total carotenoids and phenolics from sweet potato tuber, flesh and peel, and antioxidant activity were investigated. Sweet potato peel extract stood out in terms of antioxidant activity and was chosen for encapsulation by spray and freeze-drying. Experimental approach. Encapsulation is an effective method to improve phytochemical stability by entrapping the core material with a coating agent. In this study, spray and freeze-drying techniques were applied for improving the stability of bioactive compounds (carotenoids and phenolics) using whey protein as a coating material. The main advantages of the applied techniques over the other encapsulation techniques are simplicity, continuity, effectiveness, availability and applicability. Results and conclusions. Physicochemical characteristics revealed that spray drying resulted in the formation of lower size particles, better flow properties and encapsulation efficiency of carotenoids. The retention of encapsulated and non-encapsulated bioactive compounds was monitored during storage in daylight and dark conditions. Storage conditions affected the carotenoid retention, whereas higher degradation rate of all samples was observable in daylight. Phenolic compounds exhibited higher retention in all investigated samples. Degradation kinetic parameters suggest the longer shelf life of spray dried encapsulated extract and potent method for stabilization of bioactive ingredients. Novelty and scientific contribution. This study demonstrates that the spray drying technique and utilization of sweet potato peel have a big potential for the development of functional additives with improved nutritional, colour and bioactive properties

Cranberry: A good source of natural antioxidants

The influence of extracts of cranbeny fruit and mixed tea (containing 40% cranberry) on stable 1,1-diphenyl-2-picrylhydrazyl (DPPH) radicals has been investigated by electron spin resonance (ESR) spectroscopy. All investigated extracts possess very high antioxidant activity, which increased dose-dependently at mass concentrations ranging from 0.5 to 3.5 mg/ml. The high contents of phenolic s (3.60-4.52 mg/g), anthocyanins (0.23-1.52 mg/g), flavan-3-ols (1.25-3.05 mg/g) and vitamin C (0.07-0.15 mg/g) in investigated extracts indicated that these compounds significantly contributed to the antioxidant activity. All these results show that the extracts of cranberry fruit and mixed tea can be used as easily accessible source of natural antioxidants and as a possible food supplement