scholarly journals A Novel Stoichio-Kinetic Model for the DPPH• Assay: The Importance of the Side Reaction and Application to Complex Mixtures

Antioxidants ◽  
2021 ◽  
Vol 10 (7) ◽  
pp. 1019
Author(s):  
Lucrezia Angeli ◽  
Sebastian Imperiale ◽  
Yubin Ding ◽  
Matteo Scampicchio ◽  
Ksenia Morozova
Keyword(s):  
Antioxidant Activity ◽  
Kinetic Model ◽  
Rate Constant ◽  
High Resolution Mass Spectrometry ◽  
Sinapic Acid ◽  
Side Reaction ◽  
Main Reaction ◽  
Dpph Assay ◽  
Best Fitting ◽  
The Common

The 2,2-diphenyl-1-picrylhydrazyl (DPPH•) assay is widely used to determine the antioxidant activity of food products and extracts. However, the common DPPH• protocol uses a two-point measurement and does not give information about the kinetics of the reaction. A novel stoichio-kinetic model applied in this study monitors the consumption of DPPH• by common antioxidants following the second order reaction. The fitting of such decay yields the rate constant k1, which describes the main reaction between antioxidants and DPPH•, and the rate constant k2, which is attributed to a slower side reaction considering the products generated between the transient radicals (AO•) and another molecule of DPPH•. The model was first applied to antioxidant standards. Sinapic acid, Trolox and ascorbic and chlorogenic acids did not show any side reaction. Instead gallic, ferulic and caffeic acids achieved the best fitting with k2. The products of the side reaction for these compounds were confirmed and identified with high-resolution mass spectrometry. Finally, the kinetic model was applied to evaluate the antioxidant activity of eight herbal extracts. This study suggests a new kinetic approach to standardize the common DPPH• assay for the determination of antioxidant activity.

scholarly journals Evaluation of the Composition of Bioactive Compounds and Antioxidant Activity in Fourteen Apricot Varieties of North India

2017 ◽  
Vol 9 (5) ◽  
pp. 66 ◽  
Author(s):  
Sajad Mohd Wani ◽  
Peerzada Rashid Hussain ◽  
Farooq Ahmad Masoodi ◽  
Mukhtar Ahmad ◽  
Touseef Ahmad Wani ◽  
...  
Keyword(s):  
Antioxidant Activity ◽  
Bioactive Compounds ◽  
Phenolic Acids ◽  
Phenolic Acid ◽  
Radical Scavenging ◽  
Sinapic Acid ◽  
North India ◽  
Dpph Assay ◽  
Total Carotenoids ◽  
First Time

Variation in the content of bioactive compounds and antioxidant activity was evaluated in fourteen apricot varieties grown in north India. In the present study, the bioactive composition of apricot varieties of north Indian Kashmir was assessed by HPLC-MS/MS and their contribution towards free radical scavenging was assessed using DPPH, FRAP and ABTS assays. Studies revealed that content of bioactive compounds in apricot varieties was found to vary significantly (p ≤ 0.05) among cultivars. Content of total phenols was significantly (p ≤ 0.05) higher in Rakausilk variety (72.5±3.12 mg/100 g GAE) followed by Viva-gold (71.2±2.11 mg/100 g GAE) and Rakhchekarpo (69.6±1.65 mg/100 g GAE). Halman apricots exhibited the highest content of total carotenoids (12.2±2.13 mg/100 g) followed by Nugget (10.5±1.11 mg/100 g). HPLC analysis of apricot samples revealed the presence of fifteen phenolic acids in Halman, Venatchaa, Rakausilk and New Castle varieties; nine phenolic acid in Rakchekarpo and Sterling apricots; twelve phenolic acids in Shakanda, Nugget, Shakarpara and CITH-1 varieties; fourteen phenolic acid in Viva gold and Turkey varieties; seven phenolic acid in Khante and nineteen phenolic acids in CITH-2 apricots. Strong correlation existed between total phenolics and antioxidant activity for DPPH assay (r = 0.91) and ABTS radical inhibition (r = 0.86) while as moderate correlation existed for FRAP (r = 0.76). For DPPH and FRAP assays; EC50 values among apricot varieties were significantly (p ≤ 0.05) lower in Rakausilk (69.2, 123.6 mg/ml) followed by Viva Gold (74.3, 129.5 mg/ml) and Rakhchekarpo (77.4, 132.4 mg/ml). For ABTS.+ inhibition the EC50 values among apricot varieties were in the order of EC50(Rakausilk) < EC50(Khante) < EC50(Viva Gold). The present study reported the first time presence of p-coumaric acid-O-hexoside, isorhamnetin-O-glucouronide, Kaempferol-3-O-acetylhexoside, quercetin-3-O-rhamnoside, sinapic acid-O- hexoside, apigenin-7-O-glucoside, vitexin and luteolin-7-O-rutinoside compounds in apricot varieties of north India.

Phenolic Imidazole Derivatives with Dual Antioxidant/Antifungal Activity: Synthesis and Structure-Activity Relationship

2019 ◽  
Vol 15 (4) ◽  
pp. 341-351 ◽  
Author(s):  
Ana P. Bettencourt ◽  
Marián Castro ◽  
João P. Silva ◽  
Francisco Fernandes ◽  
Olga P. Coutinho ◽  
...  
Keyword(s):  
Antioxidant Activity ◽  
Antifungal Activity ◽  
Organic Molecules ◽  
Inhibitory Concentration ◽  
Yeast Species ◽  
Dpph Radical ◽  
Dpph Assay ◽  
Gram Negative ◽  
Structure Activity ◽  
Deoxyribose Degradation

Background: Previous publications show that the addition of a phenolic antioxidant to an antifungal agent, considerably enhances the antifungal activity. Objective: Synthesis of novel compounds combining phenolic units with linear or cyclic nitrogencontaining organic molecules with antioxidant/antifungal activity using methodologies previously developed in the group. Methods: Several N- [1,2-dicyano-2- (arylidenamino) vinyl]-O-alkylformamidoximes 3 were synthesized and cyclized to 4,5-dicyano-N- (N´-alcoxyformimidoyl)-2-arylimidazoles 4 upon reflux in DMF, in the presence of manganese dioxide or to 6-cyano-8-arylpurines 5 when the reagent was refluxed in acetonitrile with an excess of triethylamine. These compounds were tested for their antioxidant activity by cyclic voltammetry, DPPH radical (DPPH•) assay and deoxyribose degradation assay. The minimum inhibitory concentration (MIC) of all compounds was evaluated against two yeast species, Saccharomyces cerevisiae and Candida albicans, and against bacteria Bacillus subtilis (Gram-positive) and Escherichia coli (Gram negative). Their cytotoxicity was evaluated in fibroblasts. Results: Among the synthetised compounds, five presented higher antioxidant activity than reference antioxidant Trolox and from these compounds, four presented antifungal activity without toxic effects in fibroblasts and bacteria. Conclusion: Four novel compounds presented dual antioxidant/antifungal activity at concentrations that are not toxic to bacteria and fibroblasts. The active molecules can be used as an inspiration for further studies in this area.

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 Formulation Effects in the Antioxidant Activity of Extract from the Leaves of Cymbopogon citratus (DC) Stapf

Molecules ◽  
2021 ◽  
Vol 26 (15) ◽  
pp. 4518
Author(s):  
Raquel Sousa ◽  
Artur Figueirinha ◽  
Maria Teresa Batista ◽  
Maria Eugénia Pina
Keyword(s):  
Antioxidant Activity ◽  
Perennial Grass ◽  
Antioxidant Properties ◽  
Dosage Forms ◽  
Oral Dosage ◽  
Dpph Assay ◽  
Cymbopogon Citratus ◽  
The World ◽  
Food And Beverage ◽  
Oral Dosage Forms

Cymbopogon citratus DC (Stapf.) is a perennial grass and it is distributed around the world. It is used as a condiment for food and beverage flavouring in the form of infusions and decoctions of its dried leaves. Our previous studies have shown antioxidant, anti-inflammatory and gastroprotective activities for the infusion and its phenolic fractions. The aim of the present work was to develop oral dosage forms from a Cymbopogon citratus extract to be used as a functional food with antioxidant properties. Initially, an essential oil-free infusion was prepared, lyophilized and characterized by HPLC-PDA. Total phenols were quantified with the Folin–Ciocalteu method and the antioxidant activity was assessed by DPPH assay. Gelatine capsules containing the extract with different excipients, selected after DSC and IR trials, were prepared. A formulation exhibiting better antioxidant behaviour in a gastric environment was attained. These results suggest that the proposed formulation for this extract could be a valuable antioxidant product and, consequently, make an important contribution to “preventing” and minimizing diseases related to oxidative stress conditions.

Structural diversity of salts of terpyridine derivatives with europium(III) located in both, cation and anion, in comparison to molecular complexes

2020 ◽  
Vol 235 (8-9) ◽  
pp. 353-363
Author(s):  
Alexander E. Sedykh ◽  
Robin Bissert ◽  
Dirk G. Kurth ◽  
Klaus Müller-Buschbaum
Keyword(s):  
Thermal Properties ◽  
Crystal Packing ◽  
Side Reaction ◽  
Molecular Complexes ◽  
Structural Diversity ◽  
Organic Ligands ◽  
Ionic Complexes ◽  
Structural Variability ◽  
Dimeric Complexes ◽  
The Common

AbstractThree salts of the common composition [EuCl2(X-tpy)2][EuCl4(X-tpy)]·nMeCN were obtained from EuCl3·6H2O and the respective organic ligands (X-tpy = 4′-phenyl-2,2′:6′,2″-terpyridine ptpy, 4′-(pyridin-4-yl)-2,2′:6′,2″-terpyridine 4-pytpy, and 4′-(pyridin-3-yl)-2,2′:6′,2″-terpyridine 3-pytpy). These ionic complexes are examples of salts, in which both cation and anion contain Eu3+ with the same organic ligands and chlorine atoms coordinated. As side reaction, acetonitrile transforms into acetamide resulting in the crystallization of the complex [EuCl3(ptpy)(acetamide)] (4). Salts [EuCl2(ptpy)2][EuCl4(ptpy)]·2.34MeCN (1), [EuCl2(4-pytpy)2][EuCl4(4-pytpy)]·0.11MeCN (2), and [EuCl2(3-pytpy)2][EuCl4(3-pytpy)]·MeCN (3) crystallize in different structures (varying in space group and crystal packing) due to variation of the rear atom of the ligand to a coordinative site. Additionally, we show and compare structural variability through the dimeric complexes [Eu2Cl6(ptpy)2(N,N′-spacer)]·N,N′-spacer (5, 6, 7) obtained from [EuCl3(ptpy)(py)] by exchanging the end-on ligand pyridine with several bipyridines (4,4′-bipyridine bipy, 1,2-bis(4-pyridyl)ethane bpa, and 1,2-bis(2-pyridyl)ethylene bpe). In addition, photophysical (photoluminescence) and thermal properties are presented.

scholarly journals SYNTHESIS, CHARACTERIZATION AND ANTIOXIDANT ACTIVITY OF 2-ARYL BENZOTHIAZOLE DERIVATIVES

2018 ◽  
Vol 10 (5) ◽  
pp. 3
Author(s):  
Shaista Amin ◽  
Amrita Parle
Keyword(s):  
Antioxidant Activity ◽  
Radical Scavenging ◽  
Aromatic Aldehydes ◽  
Benzoic Acids ◽  
Dpph Assay ◽  
Abts Assay ◽  
Antioxidant Assay ◽  
Benzothiazole Derivatives ◽  
Comparable Activity ◽  
Layer Chromatography

Objective: To synthesize benzothiazole derivatives, characterize them by 1HNMR and ATIR techniques and evaluate for their antioxidant activity.Methods: In the present study 12 benzothiazole derivatives were synthesized by reacting 2-chloronitro benzene as the primary reactant with different aromatic aldehydes and benzoic acids. Reactions were monitored using thin layer chromatography technique, and the newly synthesized derivatives were characterized by ATIR and 1HNMR techniques. The antioxidant assay was performed using 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulphonic acid) or ABTS method and 2,2-diphenyl-1-picrylhydrazyl or DPPH method.Results: The antioxidant activity was found to be better in ABTS assay than DPPH assay. The compounds showed comparable activity to ascorbic acid at 100µg/ml.Conclusion: It was found that the synthesized benzothiazole derivatives showed significant radical scavenging potential.

scholarly journals Antioxidant Studies of Thiazole Ring Bearing Chalcone Derivatives

2021 ◽  
pp. 355-359
Author(s):  
Ashok Babu Kasetti ◽  
Jayesh Dwivedi ◽  
Ravindra Nagasuri
Keyword(s):  
Oxidative Stress ◽  
Antioxidant Activity ◽  
Antioxidant Activities ◽  
Thiazole Ring ◽  
Chalcone Derivatives ◽  
Antioxidant Agents ◽  
Ic50 Values ◽  
The Common ◽  
Common Problems

Oxidative stress is one of the common problems seen in a variety of diseases. Chalcones and in particular heteroaryl chalcones had reported with promising antioxidant activities. Hence, in the present work, we reported the antioxidant activity of twenty thiazole ring bearing chalcone derivatives (1-20). Among the tested compounds, compounds 17, 19 and 20 containing 2-pyridinyl, 3-pyridinyl and 2-thiazolyl scaffolds showed superior antioxidant activity than the standard with their IC50 values 4±1µg/mL, 3±1 µg/mL and 5±1 µg/mL respectively. The compound 19 is an interesting lead for the development of newer antioxidant agents.

scholarly journals Central Composite Design, Kinetic Model, Thermodynamics, and Chemical Composition of Pomelo (Citrus Maxima (Burm.) Merr.) Essential Oil Extraction by Steam Distillation

Processes ◽  
2021 ◽  
Vol 9 (11) ◽  
pp. 2075
Author(s):  
Tan Phat Dao ◽  
Thanh Viet Nguyen ◽  
Thi Yen Nhi Tran ◽  
Xuan Tien Le ◽  
Ton Nu Thuy An ◽  
...  
Keyword(s):  
Activation Energy ◽  
Kinetic Model ◽  
Essential Oil ◽  
Rate Constant ◽  
Flow Rate ◽  
Steam Distillation ◽  
Extraction Process ◽  
Oil Extraction ◽  
Extraction Time ◽  
Pomelo Peel

Pomelo peel-derived essential oils have been gaining popularity due to greater demand for stress relief therapy or hair care therapy. In this study, we first performed optimization of parameters in the pomelo essential oil extraction process on a pilot scale to gain better insights for application in larger scale production. Then extraction kinetics, activation energy, thermodynamics, and essential oil quality during the extraction process were investigated during the steam distillation process. Three experimental conditions including material mass, steam flow rate, and extraction time were taken into consideration in response surface methodology (RSM) optimization. The optimal conditions were found as follows: sample weight of 422 g for one distillation batch, steam flow rate of 2.16 mL/min and extraction time of 106 min with the coefficient of determination R2 of 0.9812. The nonlinear kinetics demonstrated the compatibility of the kinetic model with simultaneous washing and unhindered diffusion with a washing rate constant of 0.1515 min−1 and a diffusion rate constant of 0.0236 min−1. The activation energy of the washing and diffusion process was 167.43 kJ.mol−1 and 96.25 kJ.mol−1, respectively. The thermodynamic value obtained at the ΔG° value was −35.02 kJ.mol−1. The quality of pomelo peel essential oil obtained by steam distillation was characterized by its high limonene content (96.996%), determined by GC-MS.

scholarly journals Antioxidant Activity of Water Soaked in Saligrama Stone – A Preliminary Report

2021 ◽  
Vol 21 (1) ◽  
pp. 33
Author(s):  
M. R. Suchitra ◽  
S. Parthasarathy
Keyword(s):  
Antioxidant Activity ◽  
Preliminary Report ◽  
Good Health ◽  
Antioxidant Property ◽  
The Other ◽  
Plain Water ◽  
Dpph Assay ◽  
Beneficial Effects ◽  
Rare Elements

<em>Saligrama</em> otherwise called <em>Shaligram</em> or <em>Salagrama</em> is a fossilized shell stone usually recovered from the banks of the Gandaki river in Nepal. It is supposed to be a sacred symbol of Hindus. Soaking the stone in water for twenty to thirty minutes and partaking the water was considered to give good health. Hence, we mobilized two stones which were authorized as original by experts. The first one was worshipped for more than 5 years and the other one for two years. The water soaked was around 25 ml which was analysed for antioxidant activity by DPPH assay with plain water without soakage as control. The antioxidant property was significantly found in both the stones with more activity in the stone worshipped for more than 5 years. We did not standardize the volume and the duration of soakage to exact values while it was approximated to around 20 – 30 minutes. We suggest more refined studies with estimation of rare elements needs to be performed to establish the beneficial effects of this sacred <em>saligrama</em> stone.

Connecting charge transfer kinetics to device parameters of a narrow-bandgap polymer-based solar cell

2016 ◽  
Vol 18 (38) ◽  
pp. 26550-26561 ◽  
Author(s):  
Jongwoo Song ◽  
Younah Lee ◽  
Boa Jin ◽  
Jongdeok An ◽  
Hyunmin Park ◽  
...  
Keyword(s):  
Charge Transfer ◽  
Solar Cell ◽  
Kinetic Model ◽  
Rate Constant ◽  
Transfer Rate ◽  
Polymer Solar Cell ◽  
Transfer Rate Constant ◽  
Charge Transfer Rate ◽  
Narrow Bandgap

The spectroscopic charge transfer rate constant was compared with the PV properties of a polymer solar cell using a kinetic model.

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