Changes in bioactive compounds and antioxidant activity of three Amaranthus L. genotypes from a model to household processing.

Amaranthus L. leaves are consumed as vegetables and are a rich source of secondary plant metabolites. The phenolic profiles of the three analyzed genotypes by LC-Q-TOF-MS/MS and HPLC-DAD were characterized by high amounts of hydroxycinnamic glucaric and -isocitric acids. 'Gartenfuchsschwanz' (A. hybridus L.) and 'Red Callaloo' (A. tricolor L.) had similar profiles. 'Gemüse-Amaranth' (A. tricolor L.) had a high amount of caffeoylglucaric acid 4, which was isolated, and afterward identified by NMR. Its antioxidant activity, measured by TEAC, DPPH, and TPC, was similar to 5-caffeoylquinic acid, common in many plant species. The antioxidant activity of Amaranthus L. can be explained rather by their different phenolic- and ascorbic acid concentrations than by their species. Household cooking reduces antioxidant activity due to oxidation processes while leaching into cooking water could be neglected. Amaranthus L. baked into a wheat-dough-matrix showed lower phenolic concentrations, presumably due to the formation of phenol-protein-bounds and thermal degradation.

Edible Wild Vegetables Urtica dioica L. and Aegopodium podagraria L.-Antioxidants Affected by Processing.

Urtica dioica L. and Aegopodium podagraria L., also known as stinging nettle and ground elder, are edible wild green vegetables rich in bioactive and antioxidant polyphenols, vitamins, and minerals. Antioxidant activity assays (TEAC-, DPPH-, and TPC-assay) in combination with HPLC measurements, to qualify and quantify their chemical compositions, were used. Firstly, the drying methods affected the antioxidant activity of further processing stages, and outcomes were dependent on the species. Secondly, cooking increased the antioxidant activity due to higher concentrations of bioactive compounds, and released bound compounds through the rupture of cell structures. Furthermore, fridge storage (3 days at 7 °C) resulted in the lowest antioxidant activity, compared to freezer storage (30 days at -20 °C). Added 5-caffeoylquinic acid (0.3 mM) led to an increased antioxidant activity, most noticeably in freeze-dried samples. Synergistic effects of 5-caffeoylquinic acid were primary found in freeze-dried samples, analyzed fresh or after storage in the fridge. Metal-chelates can lower the antioxidant activity in plant matrices. Edible wild green vegetables are rich in polyphenols and processing can even increase their concentrations to boost the potential health effects. In general, selected quantified phenolics are not solely responsible for the antioxidant activity; minerals, processing, and interactions in plant matrices also contribute decisively.

Interactions of Ascorbic Acid, 5-Caffeoylquinic Acid, and Quercetin-3-Rutinoside in the Presence and Absence of Iron during Thermal Processing and the Influence on Antioxidant Activity.

Bioactive compounds in fruit and vegetables influence each other's antioxidant activity. Pure standards, and mixtures of the common plant compounds, namely ascorbic acid, 5-caffeoylquinic acid, and quercetin-3-rutinoside (sum 0.3 mM), in the presence and absence of iron, were analyzed pre- and post-thermal processing in an aqueous solution. Antioxidant activity was measured by total phenolic content (TPC), 1,1-diphenyl-2-picrylhydrazyl (DPPH), and 2,2'-azino-bis (3-ethylbenzothiazoline-6-sulfonic acid) (TEAC) radical-scavenging assays. Ionic ferrous iron (Fe2+) and ferric iron (Fe3+) were measured photometrically. For qualification and quantification of reaction products, HPLC was used. Results showed that thermal processing does not necessarily lead to a decreased antioxidant activity, even if the compound concentrations decreased, as then degradation products themselves have an antioxidant activity. In all used antioxidant assays the 2:1 ratio of ascorbic acid and 5-caffeoylquinic acid in the presence of iron had strong synergistic effects, while the 1:2 ratio had strong antagonistic effects. The pro-oxidant iron positively influenced the antioxidant activity in combination with the used antioxidants, while ferrous iron itself interacted with common in vitro assays for total antioxidant activity. These results indicate that the antioxidant activity of compounds is influenced by factors such as interaction with other molecules, temperature, and the minerals present.

High intake of orange juice and cola differently affects metabolic risk in healthy subjects.

BACKGROUND: Higher consumption of sugar-containing beverages has been associated with an elevated risk of type 2 diabetes and gout. Whether this equally applies to cola with an unhealthy image and orange juice (OJ) having a healthy image remains unknown. METHODS: In order to investigate whether OJ and cola differently affect metabolic risk 26 healthy adults (24.7 ± 3.2 y; BMI 23.2 ± 3.3 kg/m2) participated in a 2 × 2-wk intervention and consumed either OJ or caffeine-free cola (20% Ereq as sugar from beverages) in-between 3 meals/d at ad libitum energy intake. Glycemic control, uric acid metabolism and gut microbiota were assessed as outcome parameters. RESULTS: Fecal microbiota, body weight, basal and OGTT-derived insulin sensitivity remained unchanged in both intervention periods. Levels of uric acid were normal at baseline and did not change with 2-wk cola consumption (-0.03 ± 0.67 mg/dL; p > 0.05), whereas they decreased with OJ intervention (-0.43 ± 0.56 mg/dL; p < 0.01) due to increased uric acid excretion (+130.2 ± 130.0 mg/d; p < 0.001). Compared to OJ, consumption of cola led to a higher daylong glycemia (ΔiAUC: 36.9 ± 83.2; p < 0.05), an increase in glucose variability (ΔMAGE-Index: 0.29 ± 0.44; p < 0.05), and a lower 24 h-insulin secretion (ΔC-peptide excretion: -31.76 ± 38.61 µg/d; p < 0.001), which may be explained by a decrease in serum potassium levels (-0.11 ± 0.24 mmol/L; p < 0.05). CONCLUSION: Despite its sugar content, regular consumption of large amounts of OJ do not increase the risk of gout but may even contribute to lower uric acid levels. The etiology of impaired insulin secretion with cola consumption needs to be further investigated.

Impact of Cultivation Method and Cultivar Selection on Soluble Carbohydrates and Pungent Principles in Onions ( Allium cepa L.).

The composition of soluble carbohydrates such as fructooligosaccharides (FOS) in onions ( Allium cepa L.) plays a role regarding their digestibility, long-term storability, and processability. Qualitative and quantitative profiles of soluble carbohydrates were determined in 23 different onion samples comprising 20 cultivars grown at two different locations in 2014 and 2015. FOS concentrations were 1.1-fold higher in set grown onions than in seed grown onions ( p = 0.001). FOS levels of dehydrator cultivars were higher (overall average: 130.8 ± 42.4 g/L FOS) than those of common set and seed (61.8 ± 20.0 and 29.4 ± 14.7 g/L FOS) grown cultivars. Consequently, cultivation method (seed vs. set planting) and cultivar selection were crucial when aiming at onions with defined FOS contents. Besides FOS and other carbohydrate-related parameters, levels of alk(en)yl cysteine sulfoxides, indicating onion oil yield and pungency of onions, were determined to be different in dehydrator onions (13.1 ± 2.6 µmol/mL), seed (8.4 ± 1.3 µmol/mL), and set grown onions (7.5 ± 1.6 µmol/mL).