► DPPH assay is a common antioxidant assay. ► Variations in antiradical properties using DPPH Assay observed in literature. ► Examples highlighted with case studies along with our findings and ...remedies suggested.
Applications of antioxidants are increasing due to their multiple roles in minimising harmful effects of oxidative stress. 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging assay is routinely practiced for the assessment of antiradical properties of different compounds. A detailed literature survey revealed use of different materials and methods for DPPH assay by different investigators resulted in variation in the values of reference standards and measured parameters of new antioxidants. In the present work a detailed kinetic study of antioxidants has been performed and comprehensive results in terms of effective concentration which scavenges 50% radical (EC50), antioxidant reducing power (ARP), stoichiometry and second order rate constant (k2) values have been reported with DPPH assay. Importance of selection of appropriate reference compounds and kinetic calculations are suggested. Few case studies of standard antioxidants have been discussed to emphasise the utilisation of appropriate methodology and reference compounds.
Aqueous extracts of 30 plants were investigated for their antioxidant properties using DPPH and ABTS radical scavenging capacity assay, oxygen radical absorbance capacity (ORAC) assay, superoxide ...dismutase (SOD) assay, and ferric reducing antioxidant potential (FRAP) assay. Total phenolic content was also determined by the Folin-Ciocalteu method. Antioxidant properties and total phenolic content differed significantly among selected plants. It was found that oak (Quercus robur), pine (Pinus maritima), and cinnamon (Cinnamomum zeylanicum) aqueous extracts possessed the highest antioxidant capacities in most of the methods used, and thus could be potential rich sources of natural antioxidants. These extracts presented the highest phenolic content (300-400 mg GAE/g). Mate (Ilex paraguariensis) and clove (Eugenia caryophyllus clovis) aqueous extracts also showed strong antioxidant properties and a high phenolic content (about 200 mg GAE/g). A significant relationship between antioxidant capacity and total phenolic content was found, indicating that phenolic compounds are the major contributors to the antioxidant properties of these plants.
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•DPTU is better than BPTU in capturing DPPH• and ABTS•+ free radicals.•HAT mechanism is preferred over SET when thiourea derivatives react with HOO•.•Antioxidant ability of DPTU and ...BPTU are assessed by thermochemical and kinetic study.•Quantum chemistry calculations are consistent with the experimental results.
Antioxidant ability of thiourea derivatives was characterized based on the measurement of the color change of 2,2-diphenyl-1-picrylhydrazyl (DPPH) and 2,2′-azinobis(3-ethylbenzothiazoline-6-sulfonate) (ABTS+) when reacting with the studied compounds. The values of IC50DPPH/ IC50ABTS of DPTU (1,3-diphenyl-2-thiourea) and BPTU (1-benzyl-3-phenyl-2-thiourea) are of 0.710 ± 0.001 mM/0.044 ± 0.001 mM and 11.000 ± 0.015 mM/2.400 ± 0.021 mM, respectively. As a result, it could be concluded that DPTU could capture free radicals better than BPTU and quantum chemical calculations also confirmed this evaluation. Although bond dissociation energy values of bonds in BPTU molecule are less than those in DPTU molecule, but the reaction rates of DPTU are greater than those of BPTU when reacting with HOO (selected as a representative free radical), so the IC50 values of DPTU were smaller than IC50 of BPTU. On the basis of kinetic calculations, hydrogen atom transfer (HAT) is supposed to be a preferred mechanism over single electron transfer (SET) when thiourea derivatives reacted with free radicals. The amount of products obtained according to HAT mechanism accounts for 99.99% compared with the product amount of HAT and SET mechanisms.
The free radicals that people face in their daily activities require humans to get additional antioxidants from the outside. To overcome this problem, it is necessary to look for many sources of ...natural antioxidants considering the need for antioxidants that are increasingly needed Katimaha (K. hospita L.) is believed to have many benefits in the field of medicine. Therefore, katimaha has the potential to be used as a source of natural antioxidants. The research methods carried out were refining katimaha leaf simplicia, extraction, fractionation, antioxidant activity test with TLC plate, purification, determination of compound class, and antioxidant activity test using the DPPH method. The results showed that the active fraction of Katimaha leaf was the n-hexane fraction and the ethyl acetate fraction. Column chromatography on the active fraction found six pure eluates that had antioxidant activity, namely N1, N3, N5, E1, E2, and E4. Groups of compounds N1, N3, N5, E1 are terpenoids, group E2 eluates are tannins, while E3 eluates are flavonoid compounds. The pure eluate antioxidant activity test using the DPPH method obtained IC50 values of N1 are 40,142 ppm, N3 80,057 ppm, N5 271,643 ppm and E1 89,16 ppm, E2 124.91 ppm and E4 52.51 ppm.
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•Highly accurate QSPR models for the anti-DPPH activity of phenols obtained.•GFN1-xTB and GFN2-xTB levels of theory are compared for CDFT descriptors.•SET-PT and SPLET are the leading ...mechanisms of action for phenolic antioxidants.•Over 85% internal and external accuracy across all models with LOOCV.•RandomTree, J48 and JCHAID* algorithms are compared for predictive modelling.
Phenolic compounds (PC) are important antioxidant biomolecules for medicine and foods industries. The DDPH test is used for testing antioxidant capacity. A fully No-Code methodology is presented for building QSPR models for the anti-DPPH activity of 202 PC. Machine learning (ML) algorithms were used for dimensionality reduction (PCA, InfoGain, GainRatio, CfsSubset) and predictive model training (J48, RandomTree, JCHAID*). Conceptual Density Functional Theory (CDFT) descriptors are calculated at the GFN1-xTB and GFN2-xTB levels of theory and the resulting global reactivity descriptors are used to train the ML models. The obtained Decision Tree (DT) models all present over 85% accuracy and Substantial Agreement with Reality, both for the internal and external validation. All the developed models adhere to the OECD guidelines for regulatory QSPR developments and are discussed in a mechanistic context. This research presents a novel, simple and codeless methodology for developing highly precise predictive models for the anti-DPPH activity of PC, successfully bridging the gap between experimental chemistry, theoretical physical chemistry, and ML.
•Guava polysaccharides showed remarkably higher α-glucosidase inhibition than acarbose.•A novel polysaccharide (GP90-1B) was obtained from guava polysaccharides.•The structural characterization of ...GP90-1B was reported for the first time.•GP90-1B comprises a backbone of α-l-Ara with α-l-Ara and α-d-Glu branched chains.
To explore the chemicals responsible for the health benefits of guava, water-soluble polysaccharides were extracted including GP90 and P90. They exhibited excellent α-glucosidase inhibition activity with an EC50 of 2.27μg/mL and 0.18mg/mL. This suggests that their activities were 1379- and 17-fold higher than the positive control. The DPPH scavenging activities of GP90 was even higher than Vc at some concentrations. Upon further isolation, a novel polysaccharide termed GB90-1B was obtained. Monosaccharide analysis, methylation analysis, and NMR were used to analyze the structural characterization of GB90-1B. Structural analysis revealed that its backbone consisted of (1→5)-linked-α-l-arabinose, (1→2,3,5)-linked-α-l-arabinose and (1→3)-linked-α-l-arabinose. Branch linkages included (1→6)-linked-α-d-glucose, (1→)-linked-α-d-glucose and (1→)-linked-α-l-arabinose. The structure of the repeating unit of GP90-1B was predicted.
The aim of this study was to determine the anthocyanins, ascorbic acid content and the antiradical activity in less common fruit species native in the territory of Slovakia (black mulberries, ...cornelian cherries, blackberries, blackthorn, rowanberries) and honeyberries (Lonicera kamtschatica) originated from Kamtschatka. Anthocyanins were evaluated after extraction from solid materials with acidified ethanol or after direct solution of liquid samples with HCl in ethanol solution by spectrophotometer measurement. To evaluate the antiradical activity, a spectrophotometer method based on the reaction of antioxidants with a stable radical 2,2- diphenyl- 1- picrylhydrazyle (DPPH•) in methanol solution was used. The reduction properties of ascorbic acid are used in the measurement. The highest value of anthocyanin pigments was found out in honeyberries (Lonicera kamtschatica) of all analyzed clones. Black mulberries of the genotype M104 and cornelian cherries of the genotypes 55 a 44 are the most significant sources of ascorbic acid among analysed less common fruit species. It is an interesting fact that blackthorns (Prunus spinosa) contenting the lowest value of ascorbic acid (10.31±1.016 mg.100 g-1) and medium value of anthocyanins (1.71±0.08 g.kg-1) shows the highest level of antiradical activity (461.25±3.69 % ≈ EC50= 0.1084 ± 0.0101). A similar phenomenon was observed in honeysuckles, too. According to these results we can suppose that another flavonoids (flavonols, flavons and flavanols) can also significantly contributed to antiradical activity of the blackthorns and edible honeysuckles. In summary, analysed less known fruit species are important sources of nutritive compounds, particularly anthocyanins, ascorbic acid and show significant free radical scavenging ability.
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