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U ovom radu ispitano je deset uzoraka vina hrvatskih proizvođača metodom cikličke voltametrije u fosfatnom puferu. Staklena ugljična elektroda korištena je kao radna elektroda, a antioksidacijski kapacitet određen ovom metodom uspoređen je s antioksidacijskim kapacitetom određenim kemijskim metodama: FRAP, ABTS i DPPH. Askorbinska kiseline, koja ima sličan mehanizam oksidacije kao i polifenolni spojevi niže molekulske mase koji u svojoj strukturi sadrže orto-dihidroksi fenolnu skupinu, korištena je kao standard za određivanje antioksidacijskog kapaciteta uzoraka vina kemijskim i elektrokemijskim metodama. Antioksidacijski kapacitet iskazan je kao ekvivalent askorbinske kiseline, izražen u jedinicama mmol AAE / 100 g uzorka. Postignuta je pozitivna, srednje jaka korelacija antioksidacijskog kapaciteta između ispitanih metoda. Kod svih metoda određivanja crna vina pokazala su značajno više vrijednosti antioksidacijskog kapaciteta u odnosu na bijela i ružičasta vina. This work examined ten samples of wines of Croatian producers' with the cyclic voltammetry method in phosphate buffer. The glassy carbon electrode was used as a working electrode, and the antioxidant capacity determined by this method was compared with the antioxidant capacity determined by the following chemical methods: FRAP, ABTS and DPPH. Ascorbic acid, having a mechanism of oxidation similar to the lower molecular weight polyphenolic compounds which contain ortho-dihydroxy phenol group in their structure, was used as a standard for determining the antioxidant capacity of wine samples by chemical and electrochemical methods. Antioxidant capacity is given in the equivalents of ascorbic acid and expressed in units of mmol AAE / 100 g sample. A positive correlation of medium strength was found between antioxidant capacities obtained by the tested methods. In all tested methods, black wines have shown significantly higher values of antioxidant capacity compared to white and pink wines.

Dosadašnja istraţivanja su dokazala kako antioksidansi produţuju čovjekov ţivot na način da sprečavaju razna oboljenja, kao što su bolesti kardiovaskularnog, probavnog, imunološkog sustava te središnjeg ţivčanog sustava. Novije studije potvrđuju pozitivan učinak hrane bogate antioksidansima, međutim znanstvenici poručuju da potreba za velikom količinom antioksidansa moţe značiti da nam u organizmu nedostaje prooksidansa. Dakle, visoke koncentracije antioksidansa mogu također imati prooksidacijsku aktivnost. To se najbolje moţe vidjeti u slučaju askorbinske kiseline, koja ''postaje'' prooksidant pri vrlo visokim koncentracijama. Zato je vrlo vaţno uspostaviti ravnoteţu između antioksidansa i prooksidansa te ne dozvoliti da ona bude narušena. Također, za neke od poznatih antioksidativnih spojeva, kao što su flavonoidi, pokazano je da djeluju kao prooksidanti, kada je u spoju prisutan prijelazni metal. Antioksidacijska i prooksidacijska aktivnost tih flavonoida koju pokreće upravo prijelazni metal, u ovom slučaju bakar, ovisi o njihovim strukturama. U eksperimentalnom dijelu završnog rada korištena je brza i jednostavna DPPH metoda, a mjerenja se mogu vršiti na običnom UV-VIS spektrofotometru. DPPH metodom smo pokušali odrediti prooksidacijski karakter odabranih boroksina te ustanoviti što se događa nakon kontakta sa askorbinskom kiselinom, koja je dokazano jaki antioksidans. Previous research has shown that antioxidants prolong human life by preventing various diseases such as cardiovascular, digestive, immune and cardiovascular diseases. Recent studies confirm the positive effect of food rich in antioxidants, but scientists confirm that the need for a large amount of antioxidants can suggest a lack of prooxidants in human body. Thus, high concentrations of antioxidants may also have prooxidative activity. This is best seen in the case of ascorbic acid, which becomes' proxidant at very high concentrations. It is therefore very important to establish a balance between antioxidants and prooxidants and not allow it to be disrupted. Also, some of the known antioxidant compounds, such as flavonoids, have been shown to act as prooxidants when a transition metal is present in the compound. The antioxidant and prooxidative activity of these flavonoids initiated by the transitional metal, in this case copper, depends on their structures. In the experimental part of the final work, the quick and easy the DPPH method was used, and measurements can be made on an ordinary UV-VIS spectrophotometer. By DPPH method we tried to determine the prooxidative character of the selected boroxine and determine what happens after contact with ascorbic acid, which is proven to be strong antioxidant.

Svrha: U uvjetima in vitro željelo se procijeniti utječe li i kako primjena 20-postotnog natrijeva askorbata na deproteinizirani dentin, a za to se rabio elektronski mikroskop/rendgenska spektroskopija raspršivanja energije (SEM/EDS). Materijal i metode: Sedam ekstrahiranih humanih trećih kutnjaka odabrano je za istodobnu analizu sastava i dentinske površine uz pomoć SEM/EDS-a. Bilo je odabrano i poduzeto sljedeće: G1 – zdrav dentinski supsrat; G2 – demineralizirani dentinski supstrat demineraliziran 15 sekundi 37-postotnom ortofosfornom kiselinom prema uputi proizvođača; G3 – deproteinizirani dentinski supstrat deproteiniziran 60 sekundi uz neprekidno miješanje u 10-postotnoj vodenoj otopini natrijeva hipoklorida; G4, G5, G6 i G7 – demineralizirani i deproteinizirani dentinski supstrat primjenom 10-postotne vodene otopine natrijeva askorbata tijekom 15, 30, 60 sekundi te jednu minutu prema redoslijedu navedenih grupa. Uzorci su pregledani elektronskim mikroskopom (Quanta 2000 – Fei Company) opremljenim spektrometrom raspršujuće energije i naponom ubrzanja od 10 KV pri povećanju od 2000 X u vakuumu. Rezultati: Analiza SEM/EDS-om pokazala je progresivno odlaganje kristala natrijeva askorbata usporedno s povećanjem antioksidacijskog sredstva, stvarajući koru koja može prouzročiti zatvaranje pojedinih dentinskih tubula. Nije bilo statistički značajne razlike između G2 i G3 (p>0,05). Primjena 10-postotnog natrijva askorbata 60 sekundi smanjila je razinu kisika (P=0,029), magnezija (P=0,019) i natrija (P=0,029). Zaključak: Nakon primjene 10-postotnog natrijeva askorbata, progresivno se talože njegovi kristali i stvaraju koru na dentinskom supstratu koja začepljuje pojedine dentinske kanaliće., Objective: To evaluate in vitro the influence of application time of sodium ascorbate to 10% on the deproteinized by scanning electron microscopy/energy dispersive x-ray spectroscopy (SEM/EDS). Methods: Seven extracted human third molars were selected. For analysis of the composition of the dentin surface by SEM/EDS, 7 samples were analyzed simultaneously as follows: G1: Healthy dentin substrate, G2: Demineralized dentin substrate with 37% phosphoric acid for 15 s (demineralization), strictly following the manufacturer’s recommendations, G3: Deproteinized dentin substrate after demineralization, 10% sodium hypochlorite aqueous solution for 60 s under constant agitation (deproteinization), G4, G5, G6 and G7: demineralized, deproteinized dentin substrate after application of 10% sodium ascorbate for 15 s, 30 s, 60 s, 10 min, respectively. The samples were examined by a scanning electron microscope (Quanta 2000 - Fei Company) equipped with an energy dispersive spectrometer with acceleration voltage 10 KV at ×2,000 magnification under vacuum. Results: The SEM/EDS analysis showed progressive deposition of sodium ascorbate crystals as the application time of the antioxidant agent increased, forming crusts which can cause occlusion of some dentinal tubules. There was no statistically significant difference between G2 and G3 (P>0.05). However, the application of 10% sodium ascorbate for 60 s resulted in a decrease in the oxygen (P=0.029), magnesium (P=0.019) and sodium (P=0.029) levels. Conclusion: After application of 10% sodium ascorbate, deposition of sodium ascorbate crystals occurred progressively forming crusts on dentin substrate, which causes occlusion of some dentinal tubules.

In this experiment thirty rats were exposed to 0 (Gr. I, healthy controls) or 10 ppm arsenic (sodium arsenite) through drinking water ad lib for eight weeks after dividing them into five groups of six rats each. Rats in Gr. III, IV and V were administered a daily oral dose of cysteine, methionine or ascorbic acid 25 mg/kg body mass respectively, while those in Gr. II served as the treated control. At the end of the experimental period oxidative stress indices viz. lipid peroxides level (LPO), superoxide dismutase (SOD) and catalase (CAT) activities were estimated in blood, liver and kidneys from sacrificed rats. Arsenic exposure resulted in a significant (P0.05) effects on the body mass of rats of different groups over time. It is concluded from the present study that prophylactic co-administration of cysteine, methionine and ascorbic acid could provide tissue specific protection from oxidative injury during sub-chronic exposure to arsenic, U istraživanju su štakori bili izloženi natrijevom arsenitu (10 ppm arsena) primijenjenom u vodi za piće tijekom 8 tjedana nakon čega su bili podijeljeni u 5 skupina po 6 štakora. Štakorima u skupinama 3, 4 i 5 oralnim je putem dnevno davan cistein, metionin ili askorbinska kiselina u količini od 25 mg/kg tjelesne mase. Štakori 2. skupine poslužili su kao kontrola. Na kraju pokusa određeni su pokazatelji oksidativnog stresa i to razina lipidnog peroksida, superoksidne dismutaze i katalaze u krvi, jetri i bubrezima. Izloženost arsenu očitovala se značajnim (P0,05) na tjelesnu masu štakora različitih skupina. Zaključeno je da istodobna profilaktička primjena cisteina, metionina ili askorbinske kiseline pruža specifičnu zaštitu tkiva od oksidacijskih oštećenja uzrokovanih supkroničnim izlaganjem arsenu.