Enriched cereal bars are more effective in increasing plasma quercetin compared with quercetin from powder-filled hard capsules.

The flavonol quercetin, is one of the major flavonoids found in edible plants. The bioavailability of quercetin in humans may be influenced by the food matrix in which it is consumed as well as by its chemical and physical form. The objective of the present study was to investigate the biokinetics of quercetin from quercetin-enriched cereal bars and quercetin powder-filled hard capsules. In a randomised, single-blinded, diet-controlled cross-over study, six healthy women aged 22-28 years took a single oral dose of approximately 130 mg quercetin equivalents from either quercetin-enriched cereal bars (containing 93·3 % quercetin aglycone plus 6·7 % quercetin-4'-glucoside) or quercetin powder-filled hard capsules (100 % quercetin aglycone). Blood samples were drawn before and after quercetin administration over a 24 h period. The concentrations of quercetin and its monomethylated derivatives, isorhamnetin (3'-O-methyl quercetin) and tamarixetin (4'-O-methyl quercetin), were measured by HPLC with fluorescence detection after plasma enzymatic treatment. The systemic availability as determined by comparing the plasma concentration-time curves of quercetin was found to be five times and the cmax values six times higher after ingestion of 130 mg quercetin by quercetin-enriched cereal bars than after ingestion by quercetin capsules. In contrast, tmax did not differ significantly between the two treatments. The cmax values for isorhamnetin and tamarixetin were four and nine times higher after ingestion of quercetin by quercetin-enriched cereal bars than after ingestion by quercetin capsules. In conclusion, quercetin from quercetin-enriched cereal bars is significantly more bioavailable than from quercetin powder-filled hard capsules.

Antioxidant enzyme activities and antioxidant capacity in longissimus muscle from bulls fed diets rich in polyunsaturated fatty acids.

The effect of a treatment diet composed of grass silage and concentrate including rapeseed (with/without feeding restriction) was compared with a control diet of maize silage/grass silage (70:30) and concentrate including soybean, on the antioxidant enzyme activities of fresh longissimus muscle from German Simmental bulls. Additionally, the effect of diet on antioxidant capacity (AOC) of hydrophilic and lipophilic antioxidants was evaluated in fresh and stored beef muscle using the FRAP-ferric reducing ability and TEAC - Trolox-equivalent antioxidant capacity assays at different reaction times. Catalase and superoxide dismutase activities were significantly higher in the treatment diet groups, and glutathione peroxidase activity was not different. AOC was not affected by the diet. However, storage affected the values of FRAP and TEAC assays, and the results were time-depending. 30min were found like a minimum reaction time for both assays. Generally, AOC values of the hydrophilic antioxidants were significantly higher than lipophilic values.

Free and bound phenolic compounds in leaves of pak choi (Brassica campestris L. ssp. chinensis var. communis) and Chinese leaf mustard (Brassica juncea Coss).

Eleven pak choi cultivars and two leaf mustard cultivars grown under field conditions in China were investigated for the free polyphenol content in their outer and inner leaves, as well as in their leaf blades and leaf stalks. In most cases, there were no significant differences between the hydroxycinnamic acid derivative and flavonoid derivative contents in the outer and inner leaves for the 13 cultivars. However, the contents of blades and stalks differed: hydroxycinnamic acids and flavonoids were present in greater amounts in the leaf blade than in the leaf stalk. Trace or small amounts of flavonoids were detected in the pak choi and leaf mustard stalks. Additionally, the bound phenolic contents of two pak choi cultivars and two leaf mustard cultivars were investigated. The concentrations of cell wall-bound phenolic compounds were higher in the leaf blade than in the leaf stalk under field conditions in China. These compounds represent only a minor portion of the total phenolic contents (flavonoids and hydroxycinnamic acids) in leaf stalks (0.81-1.18%) and leaf blades (0.05-0.08%) from fresh plant material. The storage of plant samples from four Chinese cabbage cultivars resulted, in most cases, in an increase of phenolic content, within six days, at 4°C and 20°C. The increase might have been triggered by post-harvest plant stresses, which stimulate the biosynthesis of polyphenols.

Impact of fermentation on phenolic compounds in leaves of pak choi (Brassica campestris L. ssp. chinensis var. communis) and Chinese leaf mustard (Brassica juncea coss).

Four different cultivars of Chinese Brassica vegetables (two pak choi cultivars and two Chinese leaf mustard cultivars) were fermented according to a traditional Chinese method called pickling. The plant material was investigated before and after the fermentation procedure to determine the qualitative and quantitative changes in its polyphenols. A detailed description of the identified phenolic compounds of leaf mustard by HPLC-ESI-MS(n) is presented here for the first time, including hydroxycinnamic acid mono- and diglycosides (gentiobioses) and flavonoid tetraglycosides. Flavonoid derivatives with a lower molecular mass (di- and triglycosides) and aglycones of flavonoids and hydroxycinnamic acids were detected in fermented cabbages compared to the main compounds detected in nonfermented cabbages (tri- and tetraglycosides of flavonoids and hydroxycinnamic acid derivatives of malic acid, glycoside, and quinic acid). During the fermentation process, contents of flavonoid derivatives and some hydroxycinnamic acid derivatives were found to decrease. Some marginal losses of polyphenols were observed even in the kneading step of the plant material prior to the fermentation procedure. The antioxidative potential of fermented cabbages was much higher compared to that of nonfermented cabbages in the TEAC assay, but not observable in the DPPH assay. The increase of the antioxidative potential detected in the TEAC assay was attributed to the qualitative changes of polyphenols as well as other reductones potentially present.

Identification of flavonoids and hydroxycinnamic acids in pak choi varieties (Brassica campestris L. ssp. chinensis var. communis) by HPLC-ESI-MSn and NMR and their quantification by HPLC-DAD.

Twenty-eight polyphenols (11 flavonoid derivatives and 17 hydroxycinnamic acid derivatives) were detected in different cultivars of the Chinese cabbage pak choi ( Brassica campestris L. ssp. chinensis var. communis) by HPLC-DAD-ESI-MS(n). Kaempferol was found to be the major flavonoid in pak choi, glycosylated and acylated with different compounds. Smaller amounts of isorhamnetin were also detected. A structural determination was carried out by (1)H and (13)C NMR spectroscopy for the main compound, kaempferol-3-O-hydroxyferuloylsophoroside-7-O-glucoside, for the first time. Hydroxycinnamic acid derivatives were identified as different esters of quinic acid, glycosides, and malic acid. The latter ones are described for the first time in cabbages. The content of polyphenols was determined in 11 cultivars of pak choi, with higher concentrations present in the leaf blade than in the leaf stem. Hydroxycinnamic acid esters, particularly malic acid derivatives, are present in both the leaf blade and leaf stem, whereas flavonoid levels were determined only in the leaf blade.

Nitration of gamma-tocopherol in plant tissues.

Nitration of gamma-tocopherol has been suggested to be an important mechanism for the regulation and detoxification of reactive nitrogen oxide species in animal tissues. To investigate whether this reaction does also occur in plants, reversed phase high-performance liquid chromatography (HPLC) and mass spectrometry (LC-MS) were used for analysis of 5-nitro-gamma-tocopherol (5-NgammaT) in leaves and seeds. 5-nitro-gamma-tocopherol (5-NgammaT) could be detected in an in vitro system where it was most likely generated by the reaction of gamma-tocopherol with a nitric oxide radical. In vivo 5-NgammaT was identified in leaves of the Arabidopsis mutant line (vte4), which has insertion in the gene encoding gamma-tocopherol methyltransferase and consequently lacks alpha-tocopherol and accumulates high levels of gamma-tocopherol. Quantification of NOx in leaves revealed that the vte4 mutant in comparison to wild type and the mutant vte1, which does not contain any tocopherol, has a reduced NOx concentration. The level of 5-NgammaT in leaves of the vte4 mutant was shown to depend on the developmental stage and on the duration of light exposure. 5-NgammaT was also detectable in germinating seeds of Brassica napus, Nicotiana tabacum and Arabidopsis thaliana. These seeds have in common high gamma-tocopherol contents. The rate of germination at two days after imbibition inversely correlated with the gamma-tocopherol content of the seeds. The result suggests that gamma-tocopherol or its respective derivative, 5-NgammaT, may prolong early development by reducing the level of NOx.

Anthocyanin antioxidant activity and partition behavior in whey protein emulsion.

The antioxidant activities of anthocyanins and anthocyanin fractions isolated from blackcurrants, raspberries, and lingonberries were investigated in whey protein-stabilized emulsion. The extent of protein oxidation was measured by determining the loss of tryptophan fluorescence and formation of protein carbonyl compounds and that of lipid oxidation by conjugated diene hydroperoxides and hexanal analyses. The antioxidant activity of berry anthocyanins increased with an increase in concentration. Blackcurrant anthocyanins were the most potent antioxidants toward both protein and lipid oxidation at all concentrations due to the beneficial combination of delphinidin and cyanidin glycosides. Most berry anthocyanins (69.4-72.8%) partitioned into the aqueous phase of the emulsion, thus being located favorably for antioxidant action toward protein oxidation. The presence of the lipid decreased the share of anthocyanin in the aqueous phase. Thus, the structure of food affects the antioxidant activity by influencing the partitioning of the antioxidant.