Search results for "ascorbic acid"
showing 10 items of 295 documents
Spectrophotometric determination of chlorhexidine with bromocresol green by flow-injection and manual methods
1986
Abstract A spectrophotometric study of the chlorhexidine/bromocresol green/Triton X-100 system is reported; at pH 5.3, both 2:1 and 1:1 bromocresol green/chlorhexidine complexes are formed. In the manual spectrophotometric method, Beer's law is obeyed for chlorhexidine concentrations of 2.9–32.2 μg ml −1 (r.s.d. 0.4–1.3%); the molar absorptivity is 12 500 l mol −1 cm −1 . In the flow-injection method, the calibration graph is linear for the chlorhexidine range 23.0–83.9 μg ml −1 (r.s.d. 0.8%); the injection is ca. 60 h −1 . Benzocaine, acetylsalicylic acid, ascorbic acid and sucrose are tolerated at 10 −2 −10 −3 M levels. Hibitane 5% was analyzed successfully.
Chromatographic analysis of phenethylamine-antihistamine combinations using C8, C18 or cyano columns and micellar sodium dodecyl sulfate-pentanol mix…
2001
The chromatographic behaviour of binary and ternary mixtures of several phenethylamines (phenylephrine, phenylpropanolamine, ephedrine, pseudoephedrine and methoxyphenamine) and antihistamines (pheniramine, carbinoxamine, doxylamine, chlorpheniramine, dexchlorpheniramine, dexbrompheniramine, diphenhydramine, tripolidine, azatadine and phenyltoloxamine), found in cough-cold pharmaceutical preparations, was studied using C8, C18 and cyano columns, micellar mobile phases of sodium dodecyl sulfate (SDS) and pentanol and UV detection. Using a C8 column and mobile phases of 0.05 mol l-1 SDS-6% v/v pentanol or 0.15 mol l-1 SDS-2% v/v pentanol at pH 7, more than 30 different phenethylamine-antihist…
Antioxidant capacity in fruit of Citrus cultivars with marked differences in pulp coloration: Contribution of carotenoids and vitamin C.
2020
The purpose of this study was to evaluate the specific contribution of carotenoids and vitamin C to the lipophilic and hydrophilic antioxidant capacity, respectively, of the pulp of citrus fruits using the genetic diversity in pigmentation and in the carotenoid complement. To this end, six citrus varieties were selected: two mandarins, Clemenules (Citrus clementina) and Nadorcott (C. reticulata); two grapefruits (C. paradisi), Marsh and Star Ruby; and two sweet oranges (C. sinensis), Valencia late and Valencia Ruby. Total carotenoid content and composition in the pulp of fruits were very different, in relation to their color singularities. Valencia Ruby and Nadorcott had the highest caroten…
Influence of orange cultivar and mandarin postharvest storage on polyphenols, ascorbic acid and antioxidant activity during gastrointestinal digestio…
2017
Polyphenols, ascorbic acid content and antioxidant activity of two sweet oranges (Navel-N and Cara Cara-CC) and mandarin (Clementine-M) as well as their bioaccessibilities were evaluated in pulps and compared to those in fresh juice. Thus, pulps of oranges and mandarins displayed higher hesperidin (HES), narirutin (NAR), total flavonoids (TF), total phenols (TP) and antioxidant activity (AAC) than their corresponding juices. Also, CC products presented higher bioactive compounds content than N ones. Bioaccessibility of bioactive compounds and AAC were higher in pulps of both oranges and mandarin than in their corresponding juices. Oranges (N and CC) pulps and juices presented higher bioacce…
Effect of storage period under variable conditions on the chemical and physical composition and colour of Spanish refrigerated orange juices
2005
The effects of the physicochemical and quality characteristics of various minimally pasteurized refrigerated orange Spanish juices and their changes with storage time and temperature were investigated. Essential oils, acidity, conductivity, diacetyl index, hydroxymethylfurfural, formol index, viscosity and ascorbic acid varied with storage time more significantly at 10 degrees C than at 4 degrees C. Density, colour and pectinmethylesterase did not vary at 4 degrees C. Some of the parameters could be used as indicators of quality loss or spoilage of the juices. The degradation kinetics of the concentration of remaining ascorbic acid against time follows a straight line whose slope indicates …
Ascorbic acid content and transcriptional profiling of genes involved in its metabolism during development of petals, leaves, and fruits of orange (C…
2021
Citrus fruit is one of the most important contributors to the ascorbic acid (AsA) intake in humans. Here, we report a comparative analysis of AsA content and transcriptional changes of genes related to its metabolism during development of petals, leaves and fruits of Valencia Late oranges (Citrus sinensis). Petals of close flowers and at anthesis contained the highest concentration of AsA. In fruits, AsA content in the flavedo reached a maximum at color break, whereas the pulp accumulated lower levels and experienced minor fluctuations during development. AsA levels in leaves were similar to those in the flavedo at breaker stage. The transcriptional profiling of AsA biosynthetic, degradatio…
Effect of Nitrogen Fertilization on the Quality of Swiss Chard at Harvest and during Storage as Minimally Processed Produce
2014
The effects of different levels of nitrogen fertilization (0–50–100–150–200 kg/ha), minimal processing and cold storage (14 days at 4C) on yield and quality of fresh-cut Swiss chard (Beta vulgaris L. var. cicla L.) were evaluated. Increasing the level of nitrogen fertilization over 100 kg N/ha, plants had a higher fresh weight, reduced their dry matter content and resulted taller and leafier. Total and marketable yield increased linearly with increasing nitrogen level. Both nitrate and ascorbic acid content at harvest increased with increasing nitrogen supply. Nitrogen fertilization negatively affected the yield of minimal processing. No effect on appearance and quality loss during cold sto…
Comparison of voltammetric and high performance liquid chromatographic methods for ascorbic acid determination in infant formulas
1995
Abstract Two methods — voltammetric and high performance liquid Chromatographic (HPLC) — useful for determining ascorbic acid in foods, were compared to ascertain which of them could be used for routine determination of ascorbic acid in infant formulas. Both methods were used to assay 10 identical samples of an adapted cow's milk infant formula and 10 samples of soya protein formula. Precision was determined, the variance of each method was measured, and the methods were compared with each other. The variances of the two methods were not statistically different nor was there any significant difference between the results from the two methods. Therefore, it was concluded that both methods ca…
Antioxidants Response of Two Varieties of Tomato to Fungicides and Acetylsalicylic Acid Treatments
2015
The antioxidants (ascorbic acid and total phenolics) activity was evaluated as a comparative study regarding the influence of selected systemic fungicides, CuSO 4 mixture and acetylsalicylic acid on tomato fruits. Experimental crop consisted of two tomato varieties on which three types of treatments were applied. The antioxidants analysis was performed by spectrophotometric methods both for ascorbic acid and total phenolics determination. Our results showed significant differences regarding the antioxidants level in the experimental tomato crops.
Thermal frontal polymerization with a thermally released redox catalyst
2012
ABSTRACT: We studied thermal frontal polymerization using a re-dox systeminan attempt to lower the temperature of thefrontallypolymerizable system while increasing the front velocity so as toobtain a self-sustaining front in a thinner layer than without theredox components. A cobalt-containing polymer with a meltingpoint of 63 C (Intelimer 6050X11) and cumene hydroperoxidewere used with a triacrylate. The use of the Intelimer decreasedthe front velocity but allowed fronts to propagate in thinner layersand with more filler while still having a pot life of days. Nonplanarmodes of propagation occurred. Fronts propagated faster when6-O-palmitoyl- L -ascorbic acid was used as a reductant. Intere…