Riboflavin or vitamin B2 is an essential component of the coenzymes flavin mononucleotide and flavin adenine dinucleotide and is contained in numerous foods in free and mainly in conjugated forms. The physicochemical characteristics of riboflavin and its content in relevant foods are discussed as well as its reactive behavior in food under different conditions. Riboflavin is an effective trigger of reactive oxygen species and may induce photosensitized damage of food constituents, such as amino acids, proteins, vitamins, and antioxidants (polyphenols and flavonoids). Quantitative assessment of riboflavin in foods is most frequently performed by fluorimetric methods after high-performance liquid chromatography separation or by microbiological assay. An actual European standard method is described.

BACKGROUND:To evaluate health benefits attributed to Hibiscus sabdariffa L. a randomized, open-label, two-way crossover study was undertaken to compare the impact of an aqueous H. sabdariffa L. extract (HSE) on the systemic antioxidant potential (AOP; assayed by ferric reducing antioxidant power (FRAP)) with a reference treatment (water) in eight healthy volunteers. The biokinetic variables were the areas under the curve (AUC) of plasma FRAP, ascorbic acid and urate that are above the pre-dose concentration, and the amounts excreted into urine within 24 h (Ae(0-24) ) of antioxidants as assayed by FRAP, ascorbic acid, uric acid, malondialdehyde (biomarker for oxidative stress), and hippuric acid (metabolite and potential biomarker for total polyphenol intake).RESULTS:HSE caused significantly higher plasma AUC of FRAP, an increase in Ae(0-24) of FRAP, ascorbic acid and hippuric acid, whereas malondialdehyde excretion was reduced. Furthermore, the main hibiscus anthocyanins as well as one glucuronide conjugate could be quantified in the volunteers' urine (0.02% of the administered dose).CONCLUSION:The aqueous HSE investigated in this study enhanced the systemic AOP and reduced the oxidative stress in humans. Furthermore, the increased urinary hippuric acid excretion after HSE consumption indicates a high biotransformation of the ingested HSE polyphenols, most likely caused by the colonic microbiota.

The effect of tea polyphenols on the bioavailability of iron and the iron status of man is controversially discussed. Especially women prior to menopause are a vulnerable group regarding their iron status, with a vegetarian diet increasing this risk. This study aimed to determine several iron status parameters for men and women consuming a mixed diet or being vegetarians and drinking tea. In a cross-over study, the effect of tea consumption on the iron status of healthy male and female omnivorous compared to vegetarian volunteers was tested. All volunteers consumed either green tea or black tea (each 1L/d) for four weeks together with meals or avoided tea for four weeks (cross-over design). Blood samples were withdrawn prior to the one week depletion period, at the start of the intervention phase and thereafter weekly during intervention. The iron status parameters hemoglobin, hematocrit, transferrin, total iron and iron binding capacity were not affected by the consumption of tea. In contrast, plasma ferritin values were significantly reduced after tea consumption, especially in those women with basal ferritin values lower than 25μg/L, already after two weeks of intervention with tea (1L/d).

The antiproliferation activity of a black carrot anthocyanin-rich extract (BC-ARE) on human cancer cells (HT-29 colorectal adenocarcinoma and HL-60 promyelocytic leukaemia) and metabolism of its characteristic anthocyanins (acylated and nonacylated forms) in humans were investigated. Cancer cells were exposed for 24 h to 0.0-2.0 mg/mL of BC-ARE. Anthocyanin-rich extract inhibited proliferation of both types of cancer cells in a dose-dependent manner. After ingestion of a black carrot concentrate, three acylated and two nonacylated anthocyanins were excreted in the volunteers (n=4) urine (0.048% of the administered dose). The anthocyanins were characterized by HPLC-DAD-ESI-MS/MS. Urine recovery of nonacylated anthocyanins was 8-fold higher than that of acylated anthocyanins. (c) 2007 Elsevier Ltd. All rights reserved.

The concentration and the composition of secondary plant metabolites are strictly dependent on the apple varieties. In this study, twelve cloudy apple juices made from nine different cider apple cultivars of the harvests from 2001 to 2003 were produced and characterized analytically. The average values for total polyphenols (Folin and HPLC) were 1237 mg/l (822-2161 mg/l), and 520 mg/l (197-1229 mg/l), respectively. With antioxidant capacities up to 20 mmol Trolox/l (Mean 10 mmol/l, range 6-20 mmol/l), some of them matched or exceeded the values of red wine. The cultivars Bittenfelder and Bohnapfel showed the highest polyphenol concentrations. In comparison with commercial apple juices, the analyses of other chemical parameters revealed some peculiarities of apple juices made from special cider cultivars. For the sake of comparison, also apple juices of four dessert apples cultivars were investigated (Golden Delicious, Cox Orange, Granny Smith and Topaz). The polyphenol concentrations of 316-736 mg/l (Folin) and 22-221 mg/l (HPLC), respectively, as well as the antioxidative capacities (1-4 mmol/l Trolox) were far below that of cider apple varieties. The average value for the polyphenols (HPLC) of 102 mg/l in dessert apple juices was lower by a factor of five, compared to cider apple juice (average value 520 mg/l, HPLC). Boskoop had an antioxidative capacity of 6 mmol/l Trolox which is between dessert apple juices and cider apple juices. Four versions of juice were made from each table apple cultivar: cloudy direct juice, cloudy juice from concentrate, clear direct juice and clear juice from concentrate. The juices from concentrate did not differ from the direct juices in polyphenols and antioxidant capacity. On the other hand, the clarification of the apple juices had a pronounced effect on polyphenol contents and antioxidant capacities. The latter were up to 70% lower than the contents in the corresponding cloudy juices of the same cultivar. The quality of apple juice may generally be improved by using varieties with high concentrations of secondary plant metabolites. Cider apple cultivars had better antioxidant capacity than most of the commercial juices and can be used in apple juice blends. In consideration of functional fruit juices or fruit based beverages the genetic pool of classical apple varieties has to be preserved.

Lycopene, an efficient antioxidant and singlet oxygen quencher, is mainly delivered within the human diet out of tomatoes and tomato products. Processing liberates this carotenoid from complexes with proteins and thus makes it more bioavailable. Rosehip, a wild fruit which is used more often recently to produce mark, jams and juices, showed remarkable contents of lycopene (12.9–35.2 mg/100 g) with an unexpected isomer pattern.

The influence of classical and modern processing technologies on the antioxidant compounds of apple juices, predominantly polyphenols, has been studied. The change of antioxidant capacity (TEAC assay based on ABTS radical cation/Trolox) and the polyphenolic composition (HPLC) inflicted by enzymatic oxidation during mash and juice period. dejuicing, ascorbic acid dosage, separation, pasteurisation, fining with gelatin and silica sol, ultrafiltration. stabilisation of ultrafiltered apple juice using PVPP or adsorber resin as well as storage under forced conditions was investigated. The production of cloudy apple juice resulted in a loss of antioxidant capacity ranging from 20-40 % relative to freshly pressed juice (100 %), which was due to oxidation and the separation of juice solids. Juice clarification reduced the antioxidant capacity due to a complete removal of antioxidants bound to the cloud particles of the press juice and represented a major factor influencing the antioxidant capacity of the apple juice. Combination of ultrafiltration and adsorbents resulted in a great loss of polyphenols and antioxidant capacity (over 50%) whereas the classical gelatin and silica sol fining was significantly more gentle, Based on the results, recommendations for the conservation of juice polyphenols and the achievement of a high antioxidant capacity during production of apple juice can be given.

Pharmacokinetic parameters and the bioavailability of several dietary anthocyanins following consumption of red wine and red grape juice were compared in nine healthy volunteers. They were given a single oral dose of either 400 mL of red wine (279.6 mg total anthocyanins) or 400 mL of red grape juice (283.5 mg total anthocyanins). Within 7 h, the urinary excretion of total anthocyanins was 0.23 and 0.18% of the administered dose following red grape juice and red wine ingestion, respectively. Pharmacokinetic parameters derived from plasma and urine concentrations exhibited higher variability after ingestion of red grape juice. Compared to red grape juice anthocyanins, the relative bioavailability of red wine anthocyanins was calculated to be 65.7, 61.3, 61.9, 291.5, 57.1, and 76.3% for the glucosides of cyanidin, delphinidin, malvidin, peonidin, petunidin, and its sum (referred to as total anthocyanins), respectively. Bioequivalence was established for none of the anthocyanins. On a low level, urinary excretion of anthocyanins was fast, and the excretion rates seem to exhibit monoexponential characteristics over time after ingestion of both red grape juice and red wine. Due to low bioavailability, any significant contribution of anthocyanins to health protecting properties of red wine or red grape juice seems questionable, but the clinical relevance of these findings awaits further investigation.

Background: The bioavailability of carotenoids has been investigated in animal studies as well as in human studies, so far mostly for β-carotene. Only few results exist for lycopene. In recent studies, lycopene was significantly better available from processed tomatoes compared to raw tomatoes, when using daily intakes between 16.5 mg and 75 mg lycopene.

The antioxidant activity and the total phenolics content of various tea extracts were analysed. Green and black tea were brewed from 0.5 min up to 10 min under different brewing conditions (stirring the extract, chopping the tea leaves before brewing). For measuring the antioxidant activity, the Trolox equivalent antioxidant capacity (TEAC) test and the low density lipoprotein (LDL) oxidation test were used. In all cases the antioxidant activity as well as the content of the phenolics increased with the brewing time. In black tea (brewed without stirring or chopping), the total phenolics increased from 33.8 mg/100 ml after 0.5 min up to 68.4 mg/100 ml after 10 min brewing time. Stirring during brewing led to higher phenolic yields in the extract. Thus, phenolics in stirred black tea ranged from 44.5 mg/100 ml (0.5 min) to 96.7 mg/100 ml (10 min). Chopping the tea leaves resulted in the highest content of phenolics. Antioxidant activity was well correlated with the corresponding total phenolics content. The results of the LDL oxidation test varied more than those of the TEAC test.

A new sample pretreatment procedure for water and waste water samples is presented. Complexing agents inhibit the determination of metals in instrumental analysis. These reagents often contain nitrogen or organic phosphate. During digestion with peroxodisulphate/alkali = Oxisolv® in combination with microwave heating in a closed Teflon-vessel, all N and P react to nitrate and phosphate. The resulting ions can be determined with photometric, AAS, voltammetric or other methods. NTA, EDTA, DTPA, TMT, TEA, CN− and Tetra ToruMin as complexing agents were tested. In the case of Cr, Cu, Fe, Ni and Zn higher recoveries were obtained in comparison with the DIN-method (NTA as complexing agent). Due to MnO2 precipitation for Mn no values could be found.

The bioequivalence of thiamin in 2 therapeutically used preparations was tested in 10 healthy young men. Thiamin was orally administered either as lipophilic benfotiamine or as water-soluble thiamin mononitrate. Biokinetic data, measured as area under the curve and maximal concentration in plasma and hemolysate after ingestion, demonstrated a significantly improved bioavailability from the lipophilic derivative despite an ingested dose of only 40% as compared with the water-soluble salt. A superior cellular efficacy of benfotiamine was also concluded from the short-term stimulation of the thiamin-dependent transketolase activity in erythrocytes.

As raw cow's milk possesses a limited shelf-life and can also pose a threat to the consumer's health, thermal preservation techniques are customary nowadays. A range of compounds can be used for the assessment of successfulness of such treatments, so-called time temperature integrators (TTIs). Although most water-soluble vitamins are known to be depleted during heat exposure in milk, their application as TTI hasn't been investigated yet. Especially vitamin B6 with its various possible vitamers (chemical different forms that exhibit vitamin activity) might be a suitable system for a new vitamin-based TTI. Therefore, the applicability of B6 vitamers in cow's milk as a TTI system was to be evaluated in this study.A recently developed ultra-high performance liquid chromatography method for the simultaneous assessment of all relevant B6 vitamers in cow's milk was used to characterize the status and composition of B6 vitamers in a market survey (n = 78) from Austria, Germany and Czech Republic, comprising milk produced by various thermal and non-thermal preservation techniques such as pasteurization, extended shelf life, ultra-high temperature (UHT). Examining generated data using classification and regression decision trees, discrimination of UHT milk from other preservation techniques, based on the ratio of B6 vitamers was possible. Hence, representing the first report for process authentication of cow's milk based on the composition of minor nutrients (B6 vitamers).