The effect of L(+)ascorbic acid and/or sodium nitrate in nitric oxide production by hepatocytes in vitro was studied. It was demonstrated that the compounds added into an incubation medium stimulated nitric oxide production in hepatocytes. The highest concentration of nitric oxide was assayed after the incubation of the cells with sodium nitrate and L(+)ascorbic acid. It was found that the addi...

A detailed study of the oxidation of L-ascorbic acid by dioxygen and nitrite in water at pH 5.8 and 7.0, catalyzed by the octasulfophenyltetrapyrazinoporphyrazine complex of cobalt(II), was carried out using conventional spectrophotometric, low-temperature and high-pressure stopped-flow techniques. The Co(II) complex activates L-ascorbic acid through an intramolecular one-electron oxidation ste...

A chemically modified carbon paste electrode with 2-chlorobenzoyl ferrocene (2CBF) and carbon nanotube (2CBFCNPE) was employed to study the electrocatalytic oxidation of ascorbic acid in aqueous solution using cyclic voltammetry, square wave voltammetry and chronoamperometry. The diffusion coefficient (D = 1.42 × 10-6 cm2 s-1), and the kinetic parameter such as ...

Given the widespread interest in antioxidant nutrients, we have developed a new procedure that will permit the automated determination of plasma ascorbic acid (AA) concentration with a Roche Fara centrifugal analyzer. After the deproteinization of plasma with metaphosphoric acid, AA is oxidized to dehydroascorbic acid by AA oxidase. The product is coupled to o-phenylenediamine to produce a chro...

The medium used contained 3g of substrate, 150ml of 1/15M phosphate buffer and 150ml of sterile distilled water. 0.5g (dry weight) of the adapted cells was added to the medium and the whole was incubated at 30•‹ for 20 hours. For detecting the intermediate products, paper chromatography was chiefly used. For developing the nonvolatile acids, n-butanol-acetic acid-water (4:1:1) was used and the ...

An amperometric sensor was constructed, by using humic acids to immobilize Fe3+ ions on a carbon paste electrode (CPE-HA-Fe), and used for ascorbic acid (H2A) determination. The cyclic voltammogram of the electrode showed electrochemical response due to the Fe3+/Fe2+ couple at E1/2=+0.78 V vs SCE, using 0.5 mol L-1 KCl and 0.2 mol L-1 acetate/0.020 mol L-1 phosphate buffer, at pH = 5.4, as supp...

Determination of Dopamine electrochemically by direct oxidation is difficult due to the co-oxidation of ascorbic acid present in high concentration in biological fluids in the same potential window. In this report, we present a non oxidative approach to electrochemically detect dopamine with high selectivity and sensitivity using our newly developed poly (anilineboronic acid ) composite with si...

A carbon-paste electrode spiked with 1-[4-(ferrocenyl ethynyl)phenyl]-1-ethanone was constructed by the incorporation of 1-[4-(ferrocenyl ethynyl)phenyl]-1-ethanone in a graphite powder silicon oil matrix. It shown by cyclic voltammetry and double potential-step chronoamperometry, which this ferrocene derivative modified a carbon-paste electrode, can catalyze the ascorbic acid oxidation in an a...

A method for the determination of ascorbic acid in vitamin C tablets based on a very simple paptode design on TLC strips is described. This procedure is based on the reduction of iron(III) with ascorbic acid and the formation of a colorful red complex with immobilized 2,2'-dipyridyl (dipy) on TLC strips. The linear range of the system was 20-200 ppm with a detection limit of 1 ppm and a relativ...