A theoretical study of ascorbic acid oxidation andHOO˙/O2˙−radical scavenging

2017 ◽  
Vol 15 (20) ◽  
pp. 4417-4431 ◽  
Author(s):  
Yi-Jung Tu ◽  
David Njus ◽  
H. Bernhard Schlegel
Keyword(s):  
Ascorbic Acid ◽  
Theoretical Study ◽  
Radical Scavenging ◽  
Dehydroascorbic Acid ◽  
Acid Oxidation ◽  
Acid Radical

Ascorbate radical disproportionates by forming a dimer, cyclizing and dissociating to yield ascorbic acid and the most stable hydrated, bicyclic form of dehydroascorbic acid; radical scavenging by ascorbate radical can proceed by a similar mechanism.

scholarly journals THE EFFECT OF ASCORBIC ACID OXIDATION ON THE INCORPORATION OF SULFATE BY SLICES OF CALF COSTAL CARTILAGE

1958 ◽  
Vol 42 (2) ◽  
pp. 303-318 ◽  
Author(s):  
S. J. Klebanoff ◽  
D. D. Dziewiatkowski ◽  
G. J. Okinaka
Keyword(s):  
Hydrogen Peroxide ◽  
Ascorbic Acid ◽  
Sodium Azide ◽  
Costal Cartilage ◽  
Dehydroascorbic Acid ◽  
Inhibitory Effect ◽  
Considerable Extent ◽  
Acid Oxidation ◽  
Marked Inhibition ◽  
Production Of Hydrogen

A marked inhibition of the incorporation of S35-sulfate by normal calf costal cartilage was produced by potassium ascorbate in the presence of catalytic amounts of cupric ions. The effect of the various components of the ascorbic acid oxidizing system (potassium ascorbate, cupric ions, cuprous ions, hydrogen peroxide, dehydroascorbic acid) was investigated. The results of experiments in which hydrogen peroxide, catalase, or sodium azide were used singly or in combination suggest that the inhibition produced by the ascorbic acid oxidizing system is due, to a considerable extent, to the production of hydrogen peroxide. Dehydroascorbic acid was also found to inhibit the incorporation of S35-sulfate by cartilage slices. However, the gradual fall in pH which resulted from the addition of dehydroascorbic acid could account to a large extent for the inhibitory effect observed because the incorporation of S35-sulfate by cartilage slices decreases sharply as the pH is lowered. The incorporation of S35-sulfate by cartilage slices is inhibited also by increasing the concentration of phosphate.

scholarly journals Increases of Lipophilic Antioxidants and Anticancer Activity of Coix Seed Fermented by Monascus purpureus

Foods ◽  
2021 ◽  
Vol 10 (3) ◽  
pp. 566
Author(s):  
Haiying Zeng ◽  
Likang Qin ◽  
Xiaoyan Liu ◽  
Song Miao
Keyword(s):  
Anticancer Activity ◽  
Radical Scavenging ◽  
Monascus Purpureus ◽  
Acid Oxidation ◽  
Anticancer Activities ◽  
Lipophilic Extract ◽  
Coix Seed ◽  
Before And After ◽  
Health Promoting ◽  
Human Laryngeal Carcinoma

Lipophilic tocols, γ-oryzanol, and coixenolide in coix seed before and after fermentation by Monascus purpureus were determined. Antioxidant and anticancer activities of raw and fermented coix seed were evaluated using free-radical-scavenging assays and polyunsaturated fatty acid oxidation model, and human laryngeal carcinoma cell HEp2, respectively. Compared to the raw seed, the tocols, γ-oryzanol, and coixenolide contents increased approximately 4, 25, and 2 times, respectively, in the fermented coix seed. Especially, γ-tocotrienol and γ-oryzanol reached 72.5 and 655.0 μg/g in the fermented coix seed. The lipophilic extract from fermented coix seed exhibited higher antioxidant activity in scavenging free radicals and inhibiting lipid oxidation. The inhibitory concentrations for 50% cell survival (IC50) of lipophilic extract from fermented coix seed in inhibiting HEp2 cells decreased by 42%. This study showed that coix seed fermented by M. purpureus increased free and readily bioavailable lipophilic antioxidants and anticancer activity. Therefore, fermentation could enhance the efficacy of the health promoting function of coix seeds.

scholarly journals (−)-Epicatechin—An Important Contributor to the Antioxidant Activity of Japanese Knotweed Rhizome Bark Extract as Determined by Antioxidant Activity-Guided Fractionation

Antioxidants ◽  
2021 ◽  
Vol 10 (1) ◽  
pp. 133
Author(s):  
Urška Jug ◽  
Katerina Naumoska ◽  
Irena Vovk
Keyword(s):  
Antioxidant Activity ◽  
Ascorbic Acid ◽  
High Performance ◽  
Radical Scavenging ◽  
Size Exclusion ◽  
Solvent Mixtures ◽  
Japanese Knotweed ◽  
Compound Identification ◽  
Rp Hplc ◽  
Ic50 Value

The antioxidant activities of Japanese knotweed rhizome bark extracts, prepared with eight different solvents or solvent mixtures (water, methanol, 80% methanol(aq), acetone, 70% acetone(aq), ethanol, 70% ethanol(aq), and 90% ethyl acetate(aq)), were determined using a 2,2-diphenyl-1-picrylhydrazyl (DPPH) free radical-scavenging assay. Low half maximal inhibitory concentration (IC50) values (2.632–3.720 µg mL−1) for all the extracts were in the range of the IC50 value of the known antioxidant ascorbic acid at t0 (3.115 µg mL−1). Due to the highest extraction yield (~44%), 70% ethanol(aq) was selected for the preparation of the extract for further investigations. The IC50 value calculated for its antioxidant activity remained stable for at least 14 days, while the IC50 of ascorbic acid increased over time. The stability study showed that the container material was of great importance for the light-protected storage of the ascorbic acid(aq) solution in a refrigerator. Size exclusion–high-performance liquid chromatography (SEC-HPLC)–UV and reversed phase (RP)-HPLC-UV coupled with multistage mass spectrometry (MSn) were developed for fractionation of the 70% ethanol(aq) extract and for further compound identification, respectively. In the most potent antioxidant SEC fraction, determined using an on-line post-column SEC-HPLC-DPPH assay, epicatechin, resveratrol malonyl hexoside, and its in-source fragments (resveratrol and resveratrol acetyl hexoside) were tentatively identified by RP-HPLC-MSn. Moreover, epicatechin was additionally confirmed by two orthogonal methods, SEC-HPLC-UV and high-performance thin-layer chromatography (HPTLC) coupled with densitometry. Finally, the latter technique enabled the identification of (−)-epicatechin. (−)-Epicatechin demonstrated potent and stable time-dependent antioxidant activity (IC50 value ~1.5 µg mL−1) for at least 14 days.

scholarly journals Antioxidative, Antifungal and Additive Activity of the Antimicrobial Peptides Leg1 and Leg2 from Chickpea

Foods ◽  
2021 ◽  
Vol 10 (3) ◽  
pp. 585
Author(s):  
Marie-Louise Heymich ◽  
Laura Nißl ◽  
Dominik Hahn ◽  
Matthias Noll ◽  
Monika Pischetsrieder
Keyword(s):  
Escherichia Coli ◽  
Saccharomyces Cerevisiae ◽  
Ascorbic Acid ◽  
Bacillus Subtilis ◽  
Antifungal Activity ◽  
Antimicrobial Peptides ◽  
Antioxidative Activity ◽  
Radical Scavenging ◽  
Cytotoxic Effects ◽  
Zygosaccharomyces Bailii

The fight against food waste benefits from novel agents inhibiting spoilage. The present study investigated the preservative potential of the antimicrobial peptides Leg1 (RIKTVTSFDLPALRFLKL) and Leg2 (RIKTVTSFDLPALRWLKL) recently identified in chickpea legumin hydrolysates. Checkerboard assays revealed strong additive antimicrobial effects of Leg1/Leg2 with sodium benzoate against Escherichia coli and Bacillus subtilis with fractional inhibitory concentrations of 0.625 and 0.75. Additionally, Leg1/Leg2 displayed antifungal activity with minimum inhibitory concentrations of 500/250 µM against Saccharomyces cerevisiae and 250/125 µM against Zygosaccharomyces bailii. In contrast, no cytotoxic effects were observed against human Caco-2 cells at concentrations below 2000 µM (Leg1) and 1000 µM (Leg2). Particularly Leg2 showed antioxidative activity by radical scavenging and reducing mechanisms (maximally 91.5/86.3% compared to 91.2/94.7% for the control ascorbic acid). The present results demonstrate that Leg1/Leg2 have the potential to be applied as preservatives protecting food and other products against bacterial, fungal and oxidative spoilage.

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