Oat-based breakfast cereals are a rich source of polyphenols and high in antioxidant potential

Oats are a rich source of β-glucans and bioactive phytochemicals. The established health-beneficial properties of oats have led to an increase in the consumption of oats and oat-based food products in recent years. The objective of the present study was to analyse and compare the polyphenol content and total antioxidant capacity (via FRAP (ferric ion reducing antioxidant power) and DPPH (2,2-diphenyl-1-picrylhydrazyl) inhibition) of 30 commercially available oat-based breakfast cereals. All of the breakfast cereals analysed were a significant source of polyphenols (1506–1853 μg gallic acid equivalents (GAE)/g) and antioxidants (1682–3542 μmol/l FRAP; 30–201% inhibition of DPPH compared to gallic acid standard). There was little difference between premium and budget brand varieties of the breakfast cereals. The polyphenol levels in an average serving (40 g) of an oat-based breakfast cereal are comparable to those found in fruits and vegetables. Overall, our findings suggest that consumption of oat-based breakfast cereals could be a significant contributor to the total polyphenol content and antioxidant potential of the diet.     

Isoflavone daidzein possesses no antioxidant activities in cell-free assays but induces the antioxidant enzyme catalase

Epidemiologic studies have shown that dietary intake of isoflavonones is associated with several properties beneficial to human health. It has been suggested that at least some of these effects are related to the antioxidant activity of isoflavonoids. We analyzed the antioxidant activity of the major isoflavones found in soybeans, but none of these compounds showed prominent antioxidant effects in cell-free assay systems (trolox equivalent antioxidant capacity assay and 2,2-diphenyl-1-picrylhydrazyl assay). Therefore, we examined the hypothesis that the antioxidative effects of isoflavones are caused indirectly by up-regulation of antioxidative enzymes, thereby lowering intracellular concentration of reactive oxygene species. Daidzein shows a significant induction of catalase promoter activity at 100 μmol/L in a reporter gene assay and at 200 μmol/L in Northern blot experiments. Another hypothesis for antioxidant effects caused by isoflavones is due to metabolism by intestinal bacteria. Analyzing the daidzein metabolites 3′-OH-daidzein and 6-OH-daidzein in our cell culture model, we found strong antioxidant effects (2,2-diphenyl-1-picrylhydrazyl and trolox equivalent antioxidant capacity assay). We conclude that isoflavone daidzein up-regulates the antioxidant enzyme catalase but shows only little antioxidant capacity per se. Antioxidant effects of this dietary isoflavonone may also be due to formation of the antioxidant metabolites 6-OH-daidzein and 3′-OH-daidzein.     

Characterization of phenolics,betacyanins and antioxidant activities of the seed,leaf, sprout,flower and stalk extracts of three Amaranthus species

Hydrophilic extracts from different parts including leaves, stalks, seeds, flowers and sprouts of 3 Amaranthus species (Amaranthus hypochondriacus, Amaranthus caudatus and Amaranthus cruentus) were characterized for their phytochemical profiles including the phenolics and betacyanins by UHPLC and LC–ESI–MS, and their antioxidant activities by FRAP and ORAC assays. The main betacyanins in Amaranthus samples were identified to be amaranthine and isoamaranthine. Eleven phenolic compounds (gallic acid, protocatechuic acid, chlorogenic acid, gentistic acid, 2,4-dihydroxybenzoic acid, ferulic acid, salicylic acid, rutin, ellagic acid, kaempferol-3-rutinoside and quercetin) were identified in the extracts of different parts of Amaranthus. The total phenolic content (TPC) ranged from 1.04 to 14.94 mg GAE/g DW; the total flavonoid content (TFC) ranged from 0.27 to 11.40 mg CAE/g DW; while the total betalain content (TBC) ranged from 0.07 to 20.93 mg/100 g DW. FRAP values ranged from 0.63 to 62.21 μmol AAE/g DW and ORAC ranged from 30.67 to 451.37 μmol TE/g DW. The leaves of Amaranthus showed the highest TPC, TFC, TBC, FRAP and ORAC values; while the seeds and stalks the lowest. There was a strong correlation between TPC, TBC, TFC and the antioxidant activity. The result suggests that all parts of the Amaranthus plant can be a good source of antioxidants.