scholarly journals Complexes of Copper and Iron with Pyridoxamine, Ascorbic Acid, and a Model Amadori Compound: Exploring Pyridoxamine’s Secondary Antioxidant Activity

Antioxidants ◽  
2021 ◽  
Vol 10 (2) ◽  
pp. 208
Author(s):  
Guillermo García-Díez ◽  
Roger Monreal-Corona ◽  
Nelaine Mora-Diez
Keyword(s):  
Antioxidant Activity ◽  
Ascorbic Acid ◽  
Rate Constant ◽  
Stable Complex ◽  
Aqueous Environment ◽  
Oh Radicals ◽  
Bidentate Ligands ◽  
Superoxide Radical Anion ◽  
Amadori Compound ◽  
The Stability

The thermodynamic stability of 11 complexes of Cu(II) and 26 complexes of Fe(III) is studied, comprising the ligands pyridoxamine (PM), ascorbic acid (ASC), and a model Amadori compound (AMD). In addition, the secondary antioxidant activity of PM is analyzed when chelating both Cu(II) and Fe(III), relative to the rate constant of the first step of the Haber-Weiss cycle, in the presence of the superoxide radical anion (O2•−) or ascorbate (ASC−). Calculations are performed at the M05(SMD)/6-311+G(d,p) level of theory. The aqueous environment is modeled by making use of the SMD solvation method in all calculations. This level of theory accurately reproduces the experimental data available. When put in perspective with the stability of various complexes of aminoguanidine (AG) (which we have previously studied), the following stability trends can be found for the Cu(II) and Fe(III) complexes, respectively: ASC < AG < AMD < PM and AG < ASC < AMD < PM. The most stable complex of Cu(II) with PM (with two bidentate ligands) presents a ΔGf0 value of −35.8 kcal/mol, whereas the Fe(III) complex with the highest stability (with three bidentate ligands) possesses a ΔGf0 of −58.9 kcal/mol. These complexes can significantly reduce the rate constant of the first step of the Haber-Weiss cycle with both O2•− and ASC−. In the case of the copper-containing reaction, the rates are reduced up to 9.70 × 103 and 4.09 × 1013 times, respectively. With iron, the rates become 1.78 × 103 and 4.45 × 1015 times smaller, respectively. Thus, PM presents significant secondary antioxidant activity since it is able to inhibit the production of ·OH radicals. This work concludes a series of studies on secondary antioxidant activity and allows potentially new glycation inhibitors to be investigated and compared relative to both PM and AG.

scholarly journals Theoretical Study of the Iron Complexes with Aminoguanidine: Investigating Secondary Antioxidant Activity

Antioxidants ◽  
2020 ◽  
Vol 9 (8) ◽  
pp. 756
Author(s):  
Guillermo García-Díez ◽  
Nelaine Mora-Diez
Keyword(s):  
Antioxidant Activity ◽  
Rate Constant ◽  
Thermodynamic Stability ◽  
Radical Anion ◽  
Superoxide Radical ◽  
Theoretical Study ◽  
Initial Step ◽  
Stable Complex ◽  
Oh Radicals ◽  
Superoxide Radical Anion

A thorough analysis of the thermodynamic stability of various complexes of aminoguanidine (AG) with Fe(III) at a physiological pH is presented. Moreover, the secondary antioxidant activity of AG is studied with respect to its kinetic role in the Fe(III) reduction to Fe(II) when reacting with the superoxide radical anion or ascorbate. Calculations are performed at the M05(SMD)/6-311+G(d,p) level of theory. Solvent effects (water) are taken into account in both geometry optimizations and frequency calculations employing the SMD solvation method. Even though the results of this study show that AG can form an extensive number of stable complexes with Fe(III), none of these can reduce the rate constant of the initial step of the Haber–Weiss cycle when the reducing agent is O2•−. However, when the reductant is the ascorbate anion, AG is capable of reducing the rate constant of this reaction significantly, to the point of inhibiting the production of •OH radicals. In fact, the most stable complex of Fe(III) with AG, having a ∆Gf° of −37.9 kcal/mol, can reduce the rate constant of this reaction by 7.9 × 105 times. Thus, AG possesses secondary antioxidant activity relative to the Fe(III)/Fe(II) reduction with ascorbate, but not with O2•−. Similar results have also been found for AG relative to the Cu(II)/Cu(I) reduction, in agreement with experimental results.

scholarly journals Theoretical Study of the Iron Complexes with Lipoic and Dihydrolipoic Acids: Exploring Secondary Antioxidant Activity

Antioxidants ◽  
2020 ◽  
Vol 9 (8) ◽  
pp. 674
Author(s):  
Roger Monreal-Corona ◽  
Jesse Biddlecombe ◽  
Angela Ippolito ◽  
Nelaine Mora-Diez
Keyword(s):  
Antioxidant Activity ◽  
Electron Transfer ◽  
Rate Constant ◽  
Thermodynamic Stability ◽  
Rate Constants ◽  
Theoretical Study ◽  
Oh Radicals ◽  
Single Electron Transfer ◽  
Coordination Numbers ◽  
Ph Conditions

The thermodynamic stability of twenty-nine Fe(III) complexes with various deprotonated forms of lipoic (LA) and dihydrolipoic (DHLA) acids, with coordination numbers 4, 5 and 6, is studied at the M06(SMD)/6-31++G(d,p) level of theory in water under physiological pH conditions at 298.15 K. Even though the complexes with LA- are more stable than those with DHLA−, the most thermodynamically stable Fe(III) complexes involve DHLA2−. The twenty-four exergonic complexes are used to evaluate the secondary antioxidant activity of DHLA and LA relative to the Fe(III)/Fe(II) reduction by O2•− and ascorbate. Rate constants for the single-electron transfer (SET) reactions are calculated. The thermodynamic stability of the Fe(III) complexes does not fully correlate with the rate constant of their SET reactions, but more exergonic complexes usually exhibit smaller SET rate constants. Some Cu(II) complexes and their reduction to Cu(I) are also studied at the same level of theory for comparison. The Fe(III) complexes appear to be more stable than their Cu(II) counterparts. Relative to the Fe(III)/Fe(II) reduction with ascorbate, DHLA can fully inhibit the formation of •OH radicals, but not by reaction with O2•−. Relative to the Cu(II)/Cu(I) reduction with ascorbate, the effects of DHLA are moderate/high, and with O2•− they are minor. LA has minor to negligible inhibition effects in all the cases considered.

scholarly journals Strawberry Puree Functionalized with Natural Hydroxytyrosol: Effects on Vitamin C and Antioxidant Activity

Molecules ◽  
2020 ◽  
Vol 25 (24) ◽  
pp. 5829
Author(s):  
Alejandra Bermúdez-Oria ◽  
Yougourthane Bouchal ◽  
África Fernández-Prior ◽  
Blanca Vioque ◽  
Juan Fernández-Bolaños
Keyword(s):  
Antioxidant Activity ◽  
Ascorbic Acid ◽  
Vitamin C ◽  
Functional Food ◽  
Dehydroascorbic Acid ◽  
Model System ◽  
Human Diet ◽  
Low Concentrations ◽  
High Concentrations ◽  
The Stability

The natural antioxidant hydroxytyrosol (HT) was used to functionalize a strawberry puree. The effect of the antioxidant on the stability of the two bioactive forms of vitamin C (ascorbic acid-AA and dehydroascorbic acid-DHAA) in strawberry puree stored at 4 °C, compared with the effect on a model system of AA in water, was investigated. In the absence of HT, the concentration of vitamin C in strawberry puree decreased but not in the model system. Low concentrations of HT in strawberry puree (0.05 and 0.1 mg HT/g puree) stabilized vitamin C and improved its antioxidant activity. However, at high concentrations of HT (from 0.5 mg HT/g puree), although the antioxidant activity improved, degradation of vitamin C occurred. Therefore, the concentration of HT used to obtain a functionalized strawberry puree it is very important. An adequate concentration increases the antioxidant activity and protects vitamin C from degradation, developing a functional food. However, an inadequate concentration of HT affects the vitamin C content, which is essential for the human diet because it cannot be biosynthetized by the organism.

scholarly journals Polyphenols, L-Ascorbic Acid, and Antioxidant Activity in Wines from Rose Fruits (Rosa rugosa)

Molecules ◽  
2021 ◽  
Vol 26 (9) ◽  
pp. 2561
Author(s):  
Andrzej Cendrowski ◽  
Marcin Królak ◽  
Stanisław Kalisz
Keyword(s):  
Antioxidant Activity ◽  
Ascorbic Acid ◽  
Phenolic Compounds ◽  
Antioxidant Capacity ◽  
Quality Characteristics ◽  
Raw Material ◽  
Rosa Rugosa ◽  
Fruit Wine ◽  
High Antioxidant Activity ◽  
The Stability

The aim of the present study was to determine the influence of the winemaking process on the antioxidant potential and content of phenolic compounds and L-ascorbic acid in wines from the fruits of Rosa rugosa. The results obtained in this study clearly indicate that the fruits of the Rosa rugosa are a desirable raw material for the production of fruit wine. The parameters of the technological process of producing wines from rose fruits had a diversified influence on the tested quality characteristics. Aged wines contained phenolics levels of 473–958 mg/100 mL GAE. The final concentrations of ascorbic acid ranged from 61 to 155 mg/100 mL for the different variants of the wine. Wines revealed high antioxidant activity in assay with DPPH. On the basis of the obtained results, it can be assumed that all the applied variants of the winemaking process are suitable for rose fruit wine. Each variant ensured at least the stability of the antioxidant capacity.

scholarly journals AN EXPERIMENTAL AND THEORETICAL STUDY OF THE REACTIVITY OF SELECTED CATECHOLAMINES AND THEIR PRECURSORS TOWARDS ASCORBYL RADICAL

2020 ◽  
pp. 1-12
Author(s):  
Dušan Dimić ◽  
Đura Nakarada ◽  
Miloš Mojović ◽  
Jasmina Dimitrić Marković
Keyword(s):  
Antioxidant Activity ◽  
Ascorbic Acid ◽  
Structural Parameters ◽  
Hydrogen Atom Transfer ◽  
Human Organism ◽  
Vanillylmandelic Acid ◽  
Dft Methods ◽  
Ascorbyl Radical ◽  
The Stability ◽  
First Time

Ascorbyl radical is often used as a biomarker of oxidative stress in human organism. It is a product of the antioxidant activity of ascorbic acid and it is not expected to react further with biologically important molecules. For the first time, the reactivity of catecholamines and their precursors was investigated theoretically and experimentally towards ascorbyl radical and the main structural parameters governing activity were analyzed. It was shown that catechol moiety plays an important role, which classifies norepinephrine and 3,4-dihydroxyphenylacetic acid as the most reactive when compared to homovanillic acid, vanillylmandelic acid, and octopamine. DFT methods have been employed to determine the most probable mechanism of the reaction. Based on the change in reaction enthalpy it was concluded that Hydrogen Atom Transfer (HAT) is a preferred mechanism both in water and pentyl ethanoate. The stabilization interactions in ascorbic acid, its anion and radical are carefully analyzed in order to understand the preferability of the mentioned mechanism. The stability of the ascorbyl radical is explained in detail. The results prove that ascorbyl radical is not just a product of antioxidant activity, but also a potentially harmful species in an organism.

scholarly journals Antioxidant activity of acerola extracts

2004 ◽  
Vol 22 (SI - Chem. Reactions in Foods V) ◽  
pp. S155-S158 ◽  
Author(s):  
I. Nagamine ◽  
H. Sakurai ◽  
H. T T Nguyen ◽  
M. Miyahara ◽  
J. Parkányiová ◽  
...  
Keyword(s):  
Antioxidant Activity ◽  
Ascorbic Acid ◽  
Linoleic Acid ◽  
Ferulic Acid ◽  
Phenolic Antioxidants ◽  
Zeroth Order ◽  
The Stability ◽  
In The Beginning ◽  
Β Carotene

West Indian cherries or acerola fruits (Malpighia glabra L.) are very rich in ascorbic acid, and also contain flavonoids and anthocyanins. Therefore, their antioxidant activity is interesting. Aqueous and methanolic acerola extracts increased the stability of β-carotene-linoleic acid emulsions against oxidation. Flavonoids and anthocyanins obviously enhanced the effect of ascorbic acid. The effect of natural acerola antioxidants was comparable to that of phenolic antioxidants, such as ferulic acid. During the determination of antioxidant activity in emulsions, carotene was destroyed following a complex kinetics in the beginning of oxidation, but the zeroth order kinetics in later stages of oxidation.

Sorbitol enhances the physicochemical stability of B12 vitamers

2020 ◽  
Vol 90 (5-6) ◽  
pp. 439-447 ◽  
Author(s):  
Andrew Hadinata Lie ◽  
Maria V Chandra-Hioe ◽  
Jayashree Arcot
Keyword(s):  
Ascorbic Acid ◽  
Uv Light ◽  
Heat Exposure ◽  
Water Soluble ◽  
Uv Exposure ◽  
Physicochemical Stability ◽  
Before And After ◽  
The Stability

Abstract. The stability of B12 vitamers is affected by interaction with other water-soluble vitamins, UV light, heat, and pH. This study compared the degradation losses in cyanocobalamin, hydroxocobalamin and methylcobalamin due to the physicochemical exposure before and after the addition of sorbitol. The degradation losses of cyanocobalamin in the presence of increasing concentrations of thiamin and niacin ranged between 6%-13% and added sorbitol significantly prevented the loss of cyanocobalamin (p<0.05). Hydroxocobalamin and methylcobalamin exhibited degradation losses ranging from 24%–26% and 48%–76%, respectively; added sorbitol significantly minimised the loss to 10% and 20%, respectively (p < 0.05). Methylcobalamin was the most susceptible to degradation when co-existing with ascorbic acid, followed by hydroxocobalamin and cyanocobalamin. The presence of ascorbic acid caused the greatest degradation loss in methylcobalamin (70%-76%), which was minimised to 16% with added sorbitol (p < 0.05). Heat exposure (100 °C, 60 minutes) caused a greater loss of cyanocobalamin (38%) than UV exposure (4%). However, degradation losses in hydroxocobalamin and methylcobalamin due to UV and heat exposures were comparable (>30%). At pH 3, methylcobalamin was the most unstable showing 79% degradation loss, which was down to 12% after sorbitol was added (p < 0.05). The losses of cyanocobalamin at pH 3 and pH 9 (~15%) were prevented by adding sorbitol. Addition of sorbitol to hydroxocobalamin at pH 3 and pH 9 reduced the loss by only 6%. The results showed that cyanocobalamin was the most stable, followed by hydroxocobalamin and methylcobalamin. Added sorbitol was sufficient to significantly enhance the stability of cobalamins against degradative agents and conditions.

Instant 99mTc-Labelled Glucoheptonate Kit for Kidney Imaging

1983 ◽  
Vol 22 (05) ◽  
pp. 246-250 ◽  
Author(s):  
M. Al-Hilli ◽  
H. M. A. Karim ◽  
M. H. S. Al-Hissoni ◽  
M. N. Jassim ◽  
N. H. Agha
Keyword(s):  
Sodium Hydroxide Solution ◽  
Normal Subjects ◽  
Organ Distribution ◽  
Stable Complex ◽  
Scintillation Camera ◽  
Ph Adjustment ◽  
The Mean ◽  
The Stability ◽  
Kidney Imaging ◽  
Mean Concentration

Gelchromatography column scanning has been used to study the fractions of reduced hydrolyzed 99mTc, 99mTc-pertechnetate and 99mTc-chelate in a 99mTc-glucoheptonate (GH) preparation. A stable high labelling yield of 99mTc-GH complex in the radiopharmaceutical has been obtained with a concentration of 40-50 mg of glucoheptonic acid-calcium salt and not less than 0.45 mg of SnCl2 2 H2O at an optimal pH between 6.5 and 7.0. The stability of the complex has been found significantly affected when sodium hydroxide solution was used for the pH adjustment. However, an alternative procedure for final pH adjustment of the preparation has been investigated providing a stable complex for the usual period of time prior to the injection. The organ distribution and the blood clearance data of 99mTc-GH in rabbits were relatively similar to those reported earlier. The mean concentration of the radiopharmaceutical in both kidneys has been studied in normal subjects for one hour with a scintillation camera and the results were satisfactory.

Variation of Phytochemicals Content in Pulp and Skin of Seven Romanian Apple Cultivars

2017 ◽  
Vol 68 (3) ◽  
pp. 474-477
Author(s):  
Lacramioara Oprica ◽  
Doina Atofanei ◽  
Vladimir Poroch
Keyword(s):  
Antioxidant Activity ◽  
Ascorbic Acid ◽  
Anthocyanin Content ◽  
Colour Intensity ◽  
Total Polyphenol ◽  
Valuable Source ◽  
Golden Delicious ◽  
Apple Cultivars ◽  
Apple Fruits

The amounts of anthocyanins, flavonoids, total polyphenol and ascorbic acid in seven apple cultivars from Romania were investigated. The amounts of polyphenol and flavonoids in pulp and skin of apple cultivars ranged between 17.18�7.52 mg GAE/g DW and 20.10�11.06 mg CE/g DW as well as 3.64�1.18 mg GAE/g DW and 10.31�5.57 mg CE/g DW, respectively. The highest and smallest values of ascorbic acid both in the skin and the pulp were observed in the cultivars Mutsu and Starkrimson. The anthocyanin content is positively correlated with the colour intensity of the apple epicarp, being about three-fold higher in Prima than Golden Delicious cultivar. The better antioxidant activity provided by the content of polyphenol, ascorbic acid and flavonoids was in apple fruits of Mutsu cultivar and for this reason it should be regarded as a valuable source of antioxidants.

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