The stability of Fe(III)-As(V) co-precipitate in the presence of ascorbic acid: Effect of pH and Fe/As molar ratio

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.

Download Full-text

Label-free proteomic analysis revealed the mechanisms of protein oxidation induced by hydroxyl radicals in whiteleg shrimp (Litopenaeus vannamei) muscle

Food & Function ◽

10.1039/d1fo00380a ◽

2021 ◽

Author(s):

Hui-min Lin ◽

Xue-er Qi ◽

Shan-shan Shui ◽

Soottawat Benjakul ◽

Santiago P. Aubourg ◽

...

Keyword(s):

Ascorbic Acid ◽

Hydroxyl Radicals ◽

Litopenaeus Vannamei ◽

Protein Oxidation ◽

Proteomic Analysis ◽

Muscle Proteins ◽

Label Free ◽

Whiteleg Shrimp ◽

The Stability ◽

Oxidative Effects

The oxidative effects of hydroxyl radicals derived from a FeCl3/ascorbic acid/H2O2 system on the stability of muscle proteins in peeled shrimp (Litopenaeus vannamei) were investigated.

Download Full-text

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

Antioxidants ◽

10.3390/antiox10020208 ◽

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.

Download Full-text

Charge Transfer Complexes of Ketotifen with 2,3-Dichloro-5,6-dicyano-p-benzoquinone and 7,7,8,8-Tetracyanoquodimethane: Spectroscopic Characterization Studies

Molecules ◽

10.3390/molecules26072039 ◽

2021 ◽

Vol 26 (7) ◽

pp. 2039

Author(s):

Gamal A. E. Mostafa ◽

Ahmed Bakheit ◽

Najla AlMasoud ◽

Haitham AlRabiah

Keyword(s):

Charge Transfer ◽

Spectroscopic Characterization ◽

Molar Ratio ◽

Charge Transfer Complexes ◽

Physical Parameters ◽

Spectrophotometric Methods ◽

Theoretical Approaches ◽

The Stability ◽

Ct Complexes

The reactions of ketotifen fumarate (KT) with 2,3-dichloro-5,6-dicyano-p-benzoquinone (DDQ) and 7,7,8,8-tetracyanoquinodimethane (TCNQ) as π acceptors to form charge transfer (CT) complexes were evaluated in this study. Experimental and theoretical approaches, including density function theory (DFT), were used to obtain the comprehensive, reliable, and accurate structure elucidation of the developed CT complexes. The CT complexes (KT-DDQ and KT-TCNQ) were monitored at 485 and 843 nm, respectively, and the calibration curve ranged from 10 to 100 ppm for KT-DDQ and 2.5 to 40 ppm for KT-TCNQ. The spectrophotometric methods were validated for the determination of KT, and the stability of the CT complexes was assessed by studying the corresponding spectroscopic physical parameters. The molar ratio of KT:DDQ and KT:TCNQ was estimated at 1:1 using Job’s method, which was compatible with the results obtained using the Benesi–Hildebrand equation. Using these complexes, the quantitative determination of KT in its dosage form was successful.

Download Full-text

Studies on the Coordination Reaction of VO2+ and Tannic Acid in the Tannin Extract Desulfurization

Applied Mechanics and Materials ◽

10.4028/www.scientific.net/amm.239-240.1573 ◽

2012 ◽

Vol 239-240 ◽

pp. 1573-1576

Author(s):

Zhu Qing Gao ◽

Xiao Dong Cai ◽

Kai Cheng Ling

Keyword(s):

Stability Constants ◽

Tannic Acid ◽

Ph Value ◽

Protonation Constants ◽

Conditional Stability ◽

Tannin Extract ◽

Acid Effect ◽

Different Temperatures ◽

The Stability ◽

Apparent Stability

At different temperatures, the protonation constants of tannic acid and the complex apparent stability constants between tannic acid and VO2+ were determined by using pH potentimetric method. The results showed that the protonation constants and the complex apparent stability constants slightly decreased with the raising temperature. In accordance with the pH value in the tannin extract technology, the conditional stability constants of the complex were calculated on the basis of the acid effect of tannic acid and the hydrolysis effect of VO2+. It was found that pH greatly affected the stability constants of the complex , so pH must be strictly controlled in the tannin extract technology.

Download Full-text

Investigation of the effect of pH adjustment on the stability of nanofluid

10.1063/1.5066987 ◽

2018 ◽

Cited By ~ 5

Author(s):

Sadik Umar ◽

Fauziah Sulaiman ◽

Nurhayati Abdullah ◽

Saiful Najmee Mohamad

Keyword(s):

Effect Of Ph ◽

Ph Adjustment ◽

The Stability

Download Full-text

On the stability of ascorbic acid in emulsified systems for topical and cosmetic use

International Journal of Pharmaceutics ◽

10.1016/s0378-5173(99)00228-8 ◽

1999 ◽

Vol 188 (2) ◽

pp. 233-241 ◽

Cited By ~ 163

Author(s):

M. Gallarate ◽

M.E. Carlotti ◽

M. Trotta ◽

S. Bovo

Keyword(s):

Ascorbic Acid ◽

The Stability

Download Full-text

The effect of freezing-drying, cloudiness and concentration on the keeping quality of various blackcurrant products

Agricultural and Food Science ◽

10.23986/afsci.71612 ◽

1964 ◽

Vol 36 (1) ◽

pp. 161-180

Author(s):

Taina Kuusi

Keyword(s):

Ascorbic Acid ◽

Relevant Literature ◽

Organoleptic Properties ◽

Black Currant ◽

Organoleptic Evaluation ◽

Freeze Dried ◽

Juice Concentrate ◽

The Stability ◽

And Storage

Experiments have been made in the development of various new black-currant products, such as cloudy juice, juice concentrate and various freeze-dried preparations, along with a study of the effect of these different methods of preparation on the initial quality and storage properties. The quality was assessed from the stability of ascorbic acid and colour, the aroma number, and organoleptic evaluation. Storage lasted up to 8 months. It was established that the cloudiness exercised a slight protective effect on ascorbic acid. However, the instability of the cloud meant that the appearance of the cloudy juice was less attractive than that of the clear juice. No well-founded advantage of the cloudy juice could be demonstrated. Concentration proved less suitable, as there occurred harmful changes in ascorbic acid, colour and organoleptic properties. The freezing-drying method was excellent with respect to ascorbic acid and colour. In contrast, considerable losses in aroma occurred, with consequent weakening of the organoleptic properties. This method would be of advantage only in combination with aroma recovery, and solution of the financial problems involved. The results are discussed in the light of relevant literature.

Download Full-text

Ascorbic Acid Influence on the Extraction Intensity of the Anthocyanin Pigment from Black Currant Berries and Its Stability

Food Industry ◽

10.29141/2500-1922-2020-5-4-10 ◽

2020 ◽

Vol 5 (4) ◽

pp. 68-73

Author(s):

Natalia Chesnokova ◽

Egor Ashikhmin

Keyword(s):

Ascorbic Acid ◽

Optical Density ◽

Raw Materials ◽

Solvent System ◽

Intensity Increase ◽

Anthocyanin Pigment ◽

Black Currant ◽

Plant Raw Materials ◽

Acid Effect ◽

Extraction Degree

The article considers the ascorbic acid effect on the extraction rate and stability of anthocyanin pigment exuded from black currant berries. The researchers treated defrosted and crushed black currant berries with 0.2–10.0 % solutions of ascorbic acid at temperatures of 20–90 °C for 5–150 minutes and 100 °C for 2.5 minutes, then filtered the solution out. They determined the color intensity of the solutions by the optical density using spectrophotometer SHIMADZU UV-1800 (Japan). To determine the anthocyanin pigment content, a man diluted samples with solvent system ethanol/water/hydrochloric acid (69/30/1) and measured their optical density at a wavelength of 540 nm. The authors calculate anthocyanins content in solutions using the formula and determine that the use of 0.2–1.0 % solution of ascorbic acid as an extractant leads to the extraction intensity increase of anthocyanin pigment from plant raw materials. Adding a 1.0 % ascorbic acid solution of to the system increases the extraction degree of anthocyanin pigment by 1.4 times. A further increase in the amount of ascorbic acid in the solution to 2.0–10.0 % leads to a slight increase in the extraction intensity of anthocyanin pigment. The most complete anthocyanin pigment is extracted from plant raw materials in the presence of ascorbic acid at exposure temperatures of 20-80 °C for 30 minutes and 100 °C for 2.5 minutes. An increase in the exposure time to 60-150 minutes leads to a drop in the extraction degree of anthocyanin pigment and a change in the solution color. The solution of the pigment color becomes brown.

Download Full-text

Ekstraksi dan Uji Stabilitas Zat Warna Alami dari Bayam Merah (Alternanthera amoena Voss)

KOVALEN ◽

10.22487/kovalen.2020.v6.i3.13670 ◽

2020 ◽

Vol 6 (3) ◽

pp. 212-217

Author(s):

Khairuddin ◽

Joy Noldy Baciang ◽

Indriani ◽

Nov Irmawati Inda

Keyword(s):

Sun Exposure ◽

Natural Dye ◽

Natural Dyes ◽

Stability Test ◽

Stability Testing ◽

Effect Of Ph ◽

Color Degradation ◽

The Stability ◽

Better Than

Research on the extraction and stability test of natural dye from red spinach (Alternanthera amoena Voss) has been carried out. This study aims to determine the effect of pH and length of sun exposure on the stability of the dye from red spinach. Extraction using the maceration method with ethanol solvent and measurement using a UV-Vis spectrophotometer. Stability testing is carried out at pH 2-5 and sun exposure for 1-4 hours using a dark and light container. The results obtained, at pH 2 and pH 3, anthocyanins were more stable, compared to pH 4 and 5 which had greater color degradation. In exposure to sunlight, dark containers with a degradation percentage of 31.70% were better than clear containers with a percentage of 48.78%. Keywords: Anthocyanin, red spinach, natural dyes stability.

Download Full-text