It would be desirable to establish and standardize methods that can measure the total antioxidant capacity level directly from vegetable extracts containing phenolics. Antioxidant capacity assays may be broadly classified as electron transfer (ET)- and hydrogen atom transfer (HAT)-based assays. The majority of HAT assays are kinetics-based, and involve a competitive reaction scheme in which antioxidant and substrate compete for peroxyl radicals thermally generated through the decomposition of azo compounds. ET-based assays measure the capacity of an antioxidant in the reduction of an oxidant, which changes colour when reduced. ET assays include the ABTS/TEAC, CUPRAC, DPPH, Folin-Ciocalteu and FRAP methods, each using different chromogenic redox reagents with different standard potentials. This review intends to offer a critical evaluation of existing antioxidant assays applied to phenolics, and reports the development by our research group of a simple and low-cost antioxidant capacity assay for dietary polyphenols, vitamins C and E, and human serum antioxidants, utilizing the copper(II)-neocuproine reagent as the chromogenic oxidizing agent, which we haved named the CUPRAC (cupric ion reducing antioxidant capacity) method. This method offers distinct advantages over other ET-based assays, namely the selection of working pH at physiological pH (as opposed to the Folin and FRAP methods, which work at alkaline and acidic pHs, respectively), applicability to both hydrophilic and lipophilic antioxidants (unlike Folin and DPPH), completion of the redox reactions for most common flavonoids (unlike FRAP), selective oxidation of antioxidant compounds without affecting sugars and citric acid commonly contained in foodstuffs and the capability to assay -SH bearing antioxidants (unlike FRAP). Other similar ET-based antioxidant assays that we have developed or modified for phenolics are the Fe(III)- and Ce(IV)-reducing capacity methods.

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Comparative Evaluation of Various Total Antioxidant Capacity Assays Applied to Phenolic Compounds with the CUPRAC Assay

http://www.italybylove.com/wp-content/uploads/2014/10/Polyphenol-constituents-and-antioxidant-activity-of-grape-pomace-extracts-from-five-Sicilian-red-grape-cultivars.pdf

Polyphenol constituents and antioxidant activity of grape pomace extracts from five Sicilian red grape cultivars

The study was aimed to investigate essential oil chemical composition (gas chromatography/flame ionization
detection [GC-FID] and gas chromatography/mass spectrometry [GC-MS]) and antioxidant (1,1-diphenyl-2-picrylhydrazyl free radical (DPPH) and 2,2’-azinobis--ethylbenzothiazoline-6-sulphonate [ABTS] assays) and antimicrobial (Gram-positive and Gram-negative bacteria, fungi, and yeast) activities of essential oils extracted from leaves of Mentha longifolia L. and Mentha viridis. GC-MS analysis revealed that M. longifolia was constituted by pulegone (54.41%) as a major component followed by isomenthone (12.02%), 1,8-cineole (7.41%), borneol (6.85%),and piperitenone oxide (3.19%). M. viridis was rich in carvone (50.47%), 1,8-cineole (9.14%), and limonene (4.87%).The antioxidant activity by ABTS assay showed IC50 values of 476.3 ± 11.7 and 195.1 ± 4.2 mg/L for M. longifolia and M. viridis, respectively, the DPPH assays have resulted in a moderate IC50 (>8000 mg/L and 3476.3 ± 133 mg/L for M. longifolia and M. viridis, respectively). Antimicrobial activity showed that Listeria monocytogenes and Klebsiella pneumoniae bacteria were more inhibited by the 2 essential oils tested. Escherichia coli was least susceptible. A strong activity was also observed on fungi and yeasts. Carvone, thymol, and piperitone oxide have not been detected in Tunisian M. longifolia. Camphor is reported for the 1st time for M. viridis. Antioxidant and antibacterial activities were correlated to chemical composition.

Chemical composition and antimicrobial and antioxidant activities of Mentha (longifolia L. and viridis) essential oils.

Antioxidant properties of Prangos ferulacea (L.) Lindl., Chaerophyllum macropodum Boiss. and Heracleum persicum Desf. from Apiaceae family used as food in Eastern Anatolia and their inhibitory effects on glutathione-S-transferase

The antioxidative effect of Iranian Mentha pulegium extracts and essential oil in sunflower oil

Antioxidant and 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging activities, reducing powers and the amount of total phenolic compounds of aqueous and/or methanolic extracts of some medicinal plants used in Eastern Turkey were studied. These plants are Prangos ferulacea (CASIR), Sedum sempervivoides (HOROZ LELESI), Malva neglecta (EBEMGUMECI), Cruciata taurica (SARILIK OTU), Rosa pimpinellifolia (KOYUN GOZU), Galium verum subsp. verum (MADAVUR OTU), Urtica dioica (ISIRGAN). The highest peroxidation inhibitions were shown by aqueous extracts of C. taurica and R. pimpinellifolia (IC(50): 0.00022 mg/l and IC(50): 23 mg/l, respectively). However, the highest DPPH radical scavenging activity, reducing power and the amount of phenolic compounds were shown by R. pimpinellifolia. The lowest antioxidant properties were shown by aqueous extract of M. neglecta.

Antioxidant properties of some medicinal plants: Prangos ferulacea (Apiaceae), Sedum sempervivoides (Crassulaceae), Malva neglecta (Malvaceae), Cruciata taurica (Rubiaceae), Rosa pimpinellifolia (Rosaceae), Galium verum subsp. verum (Rubiaceae), Urtica dioica (Urticaceae).

In this study, antioxidant properties of Thymus sipyleus. Boiss. subsp. sipyleus. var. sipyleus., Teucrium chamaedrys L.., Mentha longifolia. (L.) Hudson subsp. longifolia., Salvia limbata. C.A. Meyer, and Thymus fallax. Fisch. & Mey. were investigated. Antioxidant and 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging activities, reducing powers, and the amount of total phenolic compounds of the extracts were studied. The highest antioxidant activity was shown by T. chamaedrys. (decoction, IC50: 9.2 µg/ml), and the lowest one was S. limbata. (decoction, IC50: 619.5 µg/ml). The highest DPPH radical scavenging activity was shown by T. fallax. [decoction, IC50S: 56 µg/ml (IC50S is the extract concentration (µg/ml) required for 50% inhibition of the DPPH solution absorbance at 517 nm)] while the lowest one was S. limbata. (decoction, IC50S: 335.8 µg/ml). The highest reducing power and amount of total phenolic compounds was shown by T. chamaedrys. (decoction, 29.9 µg/ml ascorbic acid equivalent, ...

https://www.tandfonline.com/doi/pdf/10.1080/13880200600592061

Antioxidant Properties of Some Medicinal Lamiaceae (Labiatae) Species

Relationship between chemical structure and antioxidant activity of luteolin and its glycosides isolated from Thymus sipyleus subsp. sipyleus var. sipyleus

One triterpenic acid (ursolic acid), one phenolic acid (rosmarinic acid), and four flavonoids (luteolin, luteolin 7-O-(6”-feruloyl)-β-glucopyranoside, luteolin 5-O-β-glucopyranoside, and luteolin 7-O-β-glucuronide) were isolated from the aerial parts of Thymus sipyleus subsp. sipyleus var. sipyleus and identified by spectroscopic methods. In vitro lipid peroxidation inhibition effects of the compounds were determined using TBA test method in a bovine brain liposome system. All compounds inhibited lipid peroxidation in various degrees except for ursolic acid. The order of the lipid peroxidation activities of luteolin, its glycosides and rosmarinic acid were: Luteolin 7-O-β-glucuronide> luteolin 5-O-β-glucopyranoside> luteolin 7-O-(6”-feruloyl)β-glucopyranoside > rosmarinic acid >luteolin. However, the activity order of the compounds was completely different in DPPH radical-scavenging activity. None of the compounds shows Fe chelating activity. The results were discussed based on their chemical structures and polarities.

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Relationship Between Chemical Structure and Antioxidant Activity of Luteolin and Its Glycosides Isolated from T . sipyleus subsp. sipyleus var. sipyleus

Antioxidant and 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging activities, reducing powers and the amount of total phenolic compounds of some medicinal Asteraceae species used in folk medicine in Eastern Anatolia were studied. These species are Achillea biebersteinii, Achillea wilhelmsii, Artemisia absinthium, Artemisia austriaca, Cichorium intybus, Helichrysum arenarium subsp. rubicundum, Tripleurospermum oreades var. oreades. The highest antioxidant activity is shown by methanol extract of A. austriaca followed by water extract of A. austriaca, methanol extract of A. wilhelmsii, water extract of H. arenarium, water extract of A. biebersteinii, water extract of A. absinthium, water extract of C. intybus, water extract of A. wilhelmsii, water extract of T. oreades. The highest DPPH radical scavenging activity is also shown by methanol extract of A. austriaca followed by water extract of A. austriaca, water extract of H. arenarium, water extract of A. absinthium, water extract of A. biebersteinii, water extract of C. intybus, water extract of A. wilhelmsii, water extract of T. oreades, methanol extract of A. wilhelmsii.

http://www.e-kutuphane.teb.org.tr/pdf/tebakademi/vol1_no3_2004/6.pdf

Zeynep Terzi

Papers

Antioxidant properties of some medicinal plants: Prangos ferulacea (Apiaceae), Sedum sempervivoides (Crassulaceae), Malva neglecta (Malvaceae), Cruciata taurica (Rubiaceae), Rosa pimpinellifolia (Rosaceae), Galium verum subsp. verum (Rubiaceae), Urtica dioica (Urticaceae).

Antioxidant Properties of Some Medicinal Lamiaceae (Labiatae) Species

Relationship between chemical structure and antioxidant activity of luteolin and its glycosides isolated from Thymus sipyleus subsp. sipyleus var. sipyleus

Relationship Between Chemical Structure and Antioxidant Activity of Luteolin and Its Glycosides Isolated from T . sipyleus subsp. sipyleus var. sipyleus

Antioxidant activities and total phenolic compounds amount of some asteraceae species