ASCORBIС ACID DEGRADATION IN N, N-DIMETHYLFORMAMIDE SOLUTIONS

2020 ◽  
pp. 70-75
Author(s):  
A. V. SYROESHKIN ◽  
T. V. PLETENEVA ◽  
E. V. USPENSKAYA ◽  
I. I. SAYDINOV ◽  
O. V. LEVITSKAYA ◽  
...  
Keyword(s):  
Ascorbic Acid ◽  
Optical Rotation ◽  
Hydrolysis Product ◽  
Specific Rotation ◽  
Dimethyl Formamide ◽  
Absorption Bands ◽  
Decomposition Products ◽  
First Order ◽  
First Order Kinetics ◽  
Hydrolysis Of

Objective: Investigate the mechanisms of L-ascorbic acid transforтmation and formation of coloured enamines in N, N-dimethyl-formamide solutions. Methods: An automatic polarimeter Atago POL-1/2 was used for polarimetric investigation. Electronic spectra were recorded by UV-spectrometer Cary 60 (Agilent). The statistical analysis was carried out using the OriginPro 9.1 packages. Results: The Biot’s law violation was found in below 0.1% solutions of L-ascorbic acid (AA) in N, N-dimethylformamide (DMF). During the day, the specific rotation   of 1% AA solution varied from+37 to-1.0. Gradually, the solution acquired the red colour, and its intensity depended on the AA concentration. Spectrophotometrically, it was shown that after 15 min AA was absent in the n·10-3% solutions. The decomposition followed the first-order kinetics (k1=1.83·10-2с-1). At the same time, new absorption bands appeared at 273, 390, 533 nm. Model solutions containing dimethylamine (DMA) had a similar spectrum, and the intensity of the absorption bands increased in proportion to the concentration of DMA. Conclusion: The results show that the first step in the decomposition of ascorbic acid AA in DMF follows first-order kinetics. Numerous decomposition products are optically active compounds and reverse the sign of the optical rotation of the solution. The water resulting from the decomposition of AA is involved in the hydrolysis of the solvent. The hydrolysis product, the secondary amine DMA, interacts with the carbonyl groups of the AA decomposition products to form coloured enamines. Magnesium (II) accelerates the formation of coloured products.

Time course and vectorial nature of albumin metabolism in isolated perfused rabbit PCT

1988 ◽  
Vol 255 (3) ◽  
pp. F520-F528 ◽  
Author(s):  
C. H. Park
Keyword(s):  
Time Course ◽  
Hydrolysis Product ◽  
High Capacity ◽  
Intact Protein ◽  
Renal Metabolism ◽  
First Order ◽  
First Order Kinetics ◽  
Hydrolysis Products ◽  
Renal Tubular ◽  
Hydrolysis Of

The time course and vectorial nature of renal metabolism of albumin (Alb) were studied. The tubular absorption, accumulation, and hydrolysis of Alb and the release of the hydrolysis products were determined in the isolated rabbit proximal convoluted tubule (PCT) perfused with tritiated Alb ([3H3C]Alb) at 36.4 micrograms/ml. The Alb absorption across the apical membrane was constant (99.9 +/- 4.9 x 10(-3) ng.min-1.mm-1). In contrast, the accumulation and hydrolysis of Alb in the cells increased nonlinearly with time. The bulk of the tritium that accumulated in the cells was associated with intact [3H3C]Alb. Only the final hydrolysis products were released from the cells and these first appeared in the peritubular bath 6–7 min after the start of perfusion of the tubule with [3H3C]Alb. The hydrolysis product was not detectable in the tubule lumen. The proteolytic activity correlated linearly with the protein load to the cells, characteristic of first-order kinetics and a high-capacity system. The results suggest that the renal tubular handling of proteins proceeds from the apical to the basolateral aspect of the cell. The transcellular processing of Alb is rapid and can occur in 6–7 min. The accumulation of intact protein in the cell and the first-order kinetics of hydrolysis of the absorbed protein suggest that the rate-limiting step in proximal tubular handling of proteins may include the initial hydrolysis of protein or reside in steps that precede the hydrolysis.

Acid-catalyzed Solvolysis of Isonitriles. I

1971 ◽  
Vol 49 (14) ◽  
pp. 2455-2459 ◽  
Author(s):  
Y. Y. Lim ◽  
A. R. Stein
Keyword(s):  
Formic Acid ◽  
Acid Catalysis ◽  
Hydrolysis Product ◽  
Rate Dependence ◽  
Linear Rate ◽  
First Order ◽  
Methyl Amine ◽  
Acid Catalyzed ◽  
Pseudo First Order ◽  
Hydrolysis Of

The acid-catalyzed hydrolysis of methyl isonitrile has been examined. The initial hydrolysis product is N-methylformamide which is further hydrolyzed to methyl amine and formic acid at a much slower rate. The hydrolysis to N-methylformamide is pseudo-first order in methyl isonitrile and shows a linear rate dependence on concentration of general (buffer) acid at fixed pH. The significance of general acid-catalysis in terms of the mechanism of the hydrolysis is considered and taken as evidence for carbon protonation rather than nitrogen protonation as the initiating step.

Initial Reaction Intermediates in the Oxidation of Ascorbic Acid by Nitrous Acid

1981 ◽  
Vol 44 (1) ◽  
pp. 28-32 ◽  
Author(s):  
JAY B. FOX ◽  
ROSEMARY N. FIDDLER ◽  
AARON E. WASSERMAN
Keyword(s):  
Nitric Oxide ◽  
Ascorbic Acid ◽  
Nitrous Acid ◽  
Organic Radicals ◽  
Initial Reaction ◽  
Reaction Intermediates ◽  
Absorption Bands ◽  
Visible Absorption ◽  
Decomposition Products

Nitrite and ascorbate react to form nitric oxide at pH 5.5. In the initial stages of the reaction, seven intermediates can be identified spectrally and chromatographically; these include two colorless nitroso derivatives which contain 30–60% of the initial nitrite, two nitroso reductant derivatives absorbing at 345 and 412 nm, diketogulonic acid and two further decomposition products. None of the intermediates was paramagnetic; except for diketogulonic acid, all decomposed rapidly during or after isolation. Based on the order of appearance of the ultraviolet and visible absorption bands in the reaction mixtures, the observed characteristics of the intermediates, and the lack of organic radicals, a sequence is proposed for the initial steps in the oxidation of ascorbic acid by nitrous acid.

scholarly journals Interactions of natural antioxidants with red grape pomace anthocyanins in a liquid model matrix: Stability and copigmentation effects

2011 ◽  
Vol 17 (1) ◽  
pp. 59-66 ◽  
Author(s):  
Badherdine Sidani ◽  
Dimitris Makris
Keyword(s):  
Ascorbic Acid ◽  
Natural Antioxidants ◽  
Grape Pomace ◽  
First Order ◽  
First Order Kinetics ◽  
Model Matrix ◽  
Liquid Model ◽  
Matrix Stability ◽  
The Stability ◽  
Red Grape

The purpose of this study was an examination on the stability and colour enhancement of red grape pomace anthocyanins in a juice model matrix, and the effect of the addition of natural antioxidants. The approach was based on a juice-like liquid medium (10.1?Brix, pH 3.48), which was used as the model matrix to test the effect of the addition of natural antioxidants (L-cysteine, ascorbic acid, catechin and quercetin) on the degradability of anthocyanin pigments, extracted from grape pomace. It was found that treatment of the model solutions at 80?C induced anthocyanin decomposition, which obeyed first order kinetics. Addition of increasing amounts of antioxidants, including L-cysteine, ascorbic acid, catechin and quercetin, did not provoke a proportional impact, either positive or negative, with regard to anthocyanin stability. The best stabilising effect was seen after addition of ascorbic acid and catechin at concentrations of 4 and 2 mg L-1, respectively (P < 0.001). Quercetin, however, was demonstrated a very efficient co-pigment, inducing an increase in A520 by 63%, at pH 5.6 and a copigment-to-pigment ratio of 10.

Synthesis of anisomycin. Part I. The stereospecific synthesis of N-benzoyl-2-(p-methoxybenzyl)-3-hydroxy-4-carboxamido pyrrolidine and the absolute configuration of anisomycin

1968 ◽  
Vol 46 (7) ◽  
pp. 1101-1104 ◽  
Author(s):  
C. M. Wong
Keyword(s):  
Infrared Spectra ◽  
Absolute Configuration ◽  
Optical Rotation ◽  
Specific Rotation ◽  
Stereospecific Synthesis ◽  
Specific Optical Rotation ◽  
Synthetic Compound ◽  
The Absolute ◽  
Hydrolysis Of ◽  
Absolute Stereochemistry

L-Tyrosine was converted stereospecifically to N-benzoyl-2-(p-methoxybenzyl)-3-hydroxy-4-cyanopyrrolidine (10) which had a specific optical rotation [Formula: see text]. Anisomycin was converted also to N-benzoyl-2-(p-methoxybenzyl)-3-hydroxy-4-cyanopyrrolidine (16) which had a specific rotation [Formula: see text]. The infrared spectra of the synthetic compound and the derivative of anisomycin were superimposable with each other. This result showed that the absolute configuration of the three asymmetric centers in (10) of synthetic origin were 2S, 3S, 4S, and those in (16) were 2R, 3R, 4R. Thus, anisomycin should have the absolute stereochemistry 2R, 3S, 4S as depicted in the structure (2). Hydrolysis of the hydroxy nitriles (8) and (10) gave an identical amide (3) which should have the absolute stereochemistry 2S, 3S, 4R as shown in structure (3).

scholarly journals THE THE EFFECT OF THERMAL STERILIZATION AND EXCIPIENTS ON THE STABILITY OF ASCORBIC ACID IN AQUEOUS SOLUTIONS

2019 ◽  
pp. 313-316
Author(s):  
A. V. SYROESHKIN ◽  
T. V. PLETENEVA ◽  
E. V. USPENSKAYA ◽  
O. V. LEVITSKAYA ◽  
S. S. BARSEGYUN ◽  
...  
Keyword(s):  
Heat Treatment ◽  
Ascorbic Acid ◽  
Biological Activity ◽  
Aqueous Solutions ◽  
Radiation Treatment ◽  
Ph Value ◽  
Optical Rotation ◽  
Active Pharmaceutical Ingredient ◽  
Thermal Method ◽  
Decomposition Products

Objective: To investigate the thermal stability of aqueous solutions of L-ascorbic acid (AA) and its reactions with excipients for the improvement of the injection forms technology. Methods: Solutions of L-ascorbic acid were prepared using deuterium depleted water (DDW-«light» water, D/H=4 ppm) and natural deionized high-ohmic water (BD, D/H=140 ppm). The optical rotation was observed using an automatic polarimeter Atago POL-1/2. Electrospray tandem mass spectra were recorded by Sciex X500R QTOF. Electronic spectra were recorded by UV-spectrometer Cary 60 (Agilent). Unicellular biosensor (Spirotox-test) was used for investigation of excipients influence on the AA biological activity. The statistical analysis was carried out using the OriginPro®9 packages. Results: The results demonstrate the thermal instability of AA. The optical activity of injection forms of AA differs from model solutions with the same concentration and pH value but without heat treatment. Monitoring of solutions by the LC-ESI-MS/MS method made it possible to characterize the nature of some thermal decomposition products. Thermodynamic calculations and evaluation of biological activity (Spirotox-test) indicate that AA interacts with sulfite-ion by redox mechanisms. Excipients in AA aqueous solutions decrease, but DDW increases the biological object lifetime. Conclusion: The use of the set of physicochemical and biological methods to study the effect of heat treatment of L-ascorbic acid solutions in the presence of sulfur (IV) compounds as excipients made it possible to identify decomposition products of the active pharmaceutical ingredient. The results indicate the need to exclude sterilization of the AA injection form by the thermal method and replace it with an alternative one, for example, with gamma radiation treatment.

EFFECTS OF ASCORBIC ACID AND FERUM IONS CONCENTRATION ON THE HYDROLYSIS OF GLUCOSINOLATE AND MYROSINASE ACTIVITY IN THE WATERCRESS (Nasturtium officinale sp.)

2016 ◽  
Vol 78 (8) ◽  
Author(s):  
Syamimi Mohd Zul ◽  
Noumie Surugau
Keyword(s):  
Ascorbic Acid ◽  
Enzymatic Hydrolysis ◽  
Hydrolysis Product ◽  
Carcinogenic Activity ◽  
Nasturtium Officinale ◽  
Hydrolysis Products ◽  
Low Concentrations ◽  
Health Promoting ◽  
Hydrolysis Of ◽  
Myrosinase Activity

Watercress (Nasturtium officinale sp.) from the Brassicae family contains phenethyl glucosinolates (gluconasturtiin) as the main glucosinolate (GLS). The enzymatic hydrolysis products by naturally-occuring myrosinase produced phenethyl isothicyanate (PEITC) which reported to possess anti-carcinogenic activity. Depending on several factors, its counterpart, phenethyl nitrile (PEN) can also be formed as hydrolysis product. This study investigated the effects of adding ascorbic acid and Fe2+ ions at different concentration on the hydrolysis of gluconasturtiin. Hydrolysis products were extracted using dichloromethane and analyzed semi-quantitatively by using GCMS. The results showed that PEITC increased at the low concentration of ascorbic acid (up to 0.06M). Similarly, addition of up to 0.06M Fe2+ ions increased PEITC; higher than 0.06M inhibits the formation of PEITC. Interestingly, similar trend for the production of PEN was detected. This study also investigated myrosinase activity both by exogenous and endogenous methods at different concentrations of ascorbic acid and Fe2+ ions using standard sinigrin as subsrat. Overall, the myrosinase activity was more active at the low concentrations of ascorbic acid. Also, the exogenous method is more efficient than endogenous. This study proved that the presence of reducing agents such as ascorbic acid and Fe2+ ions during the preparation of watercress as food would affect the production of the health-promoting PEITC. 

scholarly journals Degradation kinetics and in vitro digestive stability of selected bioactive compounds from a beverage formulated with butterfly pea flowers

2022 ◽  
Vol 52 (5) ◽  
Author(s):  
Renata Oliveira Santos ◽  
Laura Monteiro Keller ◽  
Vanessa Sales de Oliveira ◽  
Carlos Alberto Bucher ◽  
José Lucena Barbosa Junior ◽  
...  
Keyword(s):  
Ascorbic Acid ◽  
Degradation Rate ◽  
Degradation Kinetics ◽  
Model Systems ◽  
First Order ◽  
Ph Values ◽  
First Order Kinetics ◽  
Butterfly Pea ◽  
Effects Of Temperature

ABSTRACT: This study evaluated the effects of temperature on the pH of extracts of ascorbic acid and anthocyanins from petals of butterfly pea, as well as their in vitro digestive stability in model systems at 60, 70, and 80 °C. The pH values significantly decreased with an increase in the temperature (P < 0.05). The findings were similar for the degradation of anthocyanins and ascorbic acid, which followed first-order kinetics in all the systems. The samples heated at 80 °C presented the highest degradation rate (kobs), as well as higher percentages of degradation at the end of digestive stability in vitro.

scholarly journals Acid Hydrolysis of Bis(2,2'; 6',2''–Terpyridyl) Iron(II) Complex in the Water Pools of CTAB/Hexane/Chloroform Reverse Micelles-A Kinetic Study in Confined Medium

2020 ◽  
Vol 15 (3) ◽  
pp. 853-860
Author(s):  
K. V. Nagalakshmi ◽  
P. Shyamala
Keyword(s):  
Ionic Strength ◽  
Acid Hydrolysis ◽  
Reverse Micelles ◽  
Order Rate Constant ◽  
Micellar Medium ◽  
First Order ◽  
First Order Kinetics ◽  
Rate Of Reaction ◽  
Kinetics Of ◽  
Hydrolysis Of

The kinetics of acid hydrolysis of bis(2,2';6',2''–terpyridyl) iron(II) complex has been studied in CTAB/Hexane/Chloroform reverse micelles. The reaction obeys first order kinetics with respect to each of the reactants at all values of W, {W= [H2O]/[CTAB]}. In the reverse micellar medium, the reaction is much slower compared to aqueous medium due to low micropolarity of the water pools which does not facilitate a reaction between reactants of same charge. The effect of variation of W {W=[H2O]/[CTAB]} at constant [CTAB] and variation of [CTAB] at fixed W has been studied. The second order rate constant (k2) of the reaction increases as the value of W increases up to W = 8.88 and remains constant thereafter and it is independent of concentration of [CTAB] at constant W. The variation of rate of reaction with W has been explained by considering variation of micropolarity and ionic strength of water pools of reverse micelles with W. Copyright © 2020 BCREC Group. All rights reserved 

Kinetics of hydrolysis of aromatic mono- and disulfonyl chlorides

1987 ◽  
Vol 65 (9) ◽  
pp. 2263-2267 ◽  
Author(s):  
Przemyslaw Sanecki ◽  
Edward Rokaszewski
Keyword(s):  
Aqueous Acetic Acid ◽  
Polarographic Method ◽  
Acid System ◽  
First Order ◽  
First Order Kinetics ◽  
Kinetics Of Hydrolysis ◽  
Consecutive Reactions ◽  
Pseudo First Order ◽  
Kinetics Of ◽  
Hydrolysis Of

A continuous polarographic method of recording instantaneous concentrations of —SO2Cl groups in an aqueous acetic acid system containing CH3CO2Na has been elaborated. Ten model monosulfonyl chlorides underwent hydrolysis according to pseudo-first order kinetics (20% H2O, 80% v.v. CH3CO2H, 0.5 mol × dm−3 CH3CO2Na). Plots of hydrolysis for seven disulfonyl dichlorides with different number of —CH3 groups have been determined. Pseudo-first order rate constants for two consecutive reactions of hydrolysis (k1 and k2) have been computed and the influence of —SO2Cl and [Formula: see text] groups on the reactivity of the second group —SO2Cl has been discussed. The mechanism of nucleophilic substitution has also been discussed.

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