Antioxidant Power Test Research Articles

Sage-called plant species sold in Turkey and their antioxidant activities

Sage is commonly consumed as a herbal tea in Anatolia, where not only Salvia species, but also Sideritis species are called "sage" by the local people. Therefore, it was decided to investigate the most common species of sage-called plants sold in aktars. Eighty-seven samples randomly purchased from 21 provinces throughout Turkey were identified, which finally led to the identification of 7 species; Salvia tomentosa, Salvia fruticosa, Sideritis congesta, Sideritis pisidica var. termessi, Sideritis arguta, Sideritis perfoliata and Sideritis libanotica subsp. linearis. Infusions prepared from all samples were preliminarily tested for their antioxidant activity and 7 representative species were further evaluated by the 2,2-diphenyl-1-picrylhydrazyl (DPPH) free radical scavenging, ferrous ion-chelating and ferric-reducing antioxidant power (FRAP) tests at 0.25, 0.50, and 1.0 mg ml-1 and for their antiacetylcholinesterase activity. The infusions were subjected to the DPPH bioautographic revelatory test, which led to the conclusion that a flavonoid derivative seemed to be responsible for the antioxidant activity in Sideritis congesta and S. pisidica var. termessi.

Evaluation of natural antioxidants of Leuzea carthamoides as a result of a screening study of 88 plant extracts from the European Asteraceae and Cichoriaceae

In recently, there has been a great interest in natural antioxidants as bioactive components of food, nutraceuticals or potential drugs against several diseases. In our study, 88 extracts from various parts of plants from European Asteraceae and Cichoriaceae were assayed for radical scavenging activity by means of DPPH (1,1-diphenyl-2-picryl hydrazyl radical) test using the SIA (Sequential injection analysis) method developed for this purpose in our laboratory. DPPH radical scavenging activity of all tested plant extracts was evaluated according to the IC50 parameter. 29 extracts exhibited IC50 value lower than 0.1 mg/mL. The leaves of Leuzea carthamoides (IC50 = 0.046 mg/mL) were chosen as the most promising sample for a subsequent phytochemical study, which resulted in isolation of seven natural compounds, namely, 4′,5,7-trihydroxy-6-methoxyflavone (hispidulin) (1), 5, 7, 3′, 4′- tetrahydroxyflavanone (eriodictyol) (2), 3′,4′,5,7-pentahydroxy-6-methoxyflavonol (patuletin) (3), eriodictyol-7-β-glucopyranoside (4), 6-hydroxykaempferol-7-O-(6″-O-acetyl-β-D-glucopyranoside) (5), 4-hydroxybenzoic acid (6) and 3,4-dihydroxybenzoic acid (protocatechuic acid) (7). Antioxidant activity of the isolated compounds was evaluated by DPPH test and ferric reducing antioxidant power (FRAP) test and compared with trolox and quercetin. Both tests evaluated the flavonoid (5) as the most active antioxidant. This result was confirmed by comparison with known data concerning the structure/activity relationships of flavonoids.

Alterations of vitamin C, total phenolics, and antioxidant capacity as affected by processing tomatoes to different products.

This study was conducted to investigate the antioxidant vitamin C, the polyphenol content, and the hydrophilic antioxidant capacity of tomato juice, baked tomatoes, tomato sauce, and tomato soup. During the production of tomato juice and during the preparation of the other tomato products, samples were taken after different times, respectively, after each particular production step. High-performance liquid chromatography was used to determine the content of vitamin C. The total phenolics content was analyzed spectrophotometrically by using the Folin-Ciocalteu method. The hydrophilic antioxidant capacity was measured by using three different methods: the Trolox equivalent antioxidant capacity assay, the ferric reducing antioxidant power test, and the photochemiluminescence assay. The vitamin C contents of the tomato products decreased during the thermal processing of tomatoes. In contrast, the total phenolics concentration and the water soluble antioxidant capacity increased.