Higher plasma quercetin levels following oral administration of an onion skin extract compared with pure quercetin dihydrate in humans.

PURPOSE: To investigate the plasma kinetics of quercetin derived from hard capsules filled with onion skin extract powder or quercetin dihydrate in humans. METHODS: In a randomized, single-blind, diet-controlled crossover study, 12 healthy subjects (six men and six women) aged 21-33 years were administered a single oral supra-nutritional dose of approximately 163 mg quercetin derived from onion skin extract powder (containing 95.3 % of total flavonoids as quercetin aglycone) or quercetin dihydrate (134 mg quercetin aglycone equivalent). Blood samples were collected before and during a 24-h period after quercetin administration. The concentrations of quercetin and its two monomethylated derivatives, isorhamnetin (3'-O-methyl quercetin), and tamarixetin (4'-O-methyl quercetin), were measured using HPLC with fluorescence detection after plasma enzymatic treatment. RESULTS: The systemic availability, determined by comparing the plasma concentration-time curves of quercetin, was 4.8 times higher, and the maximum plasma concentration (C max) was 5.4 times higher after ingestion of the onion skin extract than after ingestion of pure quercetin dihydrate. By contrast, t max did not differ significantly between the two formulations. The C max values for isorhamnetin and tamarixetin were 3.8 and 4.4 times higher, respectively, after administration of onion skin extract than after pure quercetin dihydrate. The plasma kinetics of quercetin were not significantly different in men and women. CONCLUSION: Quercetin aglycone derived from onion skin extract powder is significantly more bioavailable than that from quercetin dihydrate powder filled hard capsules.

Fast and comprehensive analysis of secondary metabolites in cocoa products using ultra high-performance liquid chromatography directly after pressurized liquid extraction.

Fast methods for the extraction and analysis of various secondary metabolites from cocoa products were developed and optimized regarding speed and separation efficiency. Extraction by pressurized liquid extraction is automated and the extracts are analyzed by rapid reversed-phase ultra high-performance liquid chromatography and normal-phase high-performance liquid chromatography methods. After extraction, no further sample treatment is required before chromatographic analysis. The analytes comprise monomeric and oligomeric flavanols, flavonols, methylxanthins, N-phenylpropenoyl amino acids, and phenolic acids. Polyphenols and N-phenylpropenoyl amino acids are separated in a single run of 33 min, procyanidins are analyzed by normal-phase high-performance liquid chromatography within 16 min, and methylxanthins require only 6 min total run time. A fourth method is suitable for phenolic acids, but only protocatechuic acid was found in relevant quantities. The optimized methods were validated and applied to 27 dark chocolates, one milk chocolate, two cocoa powders and two food supplements based on cocoa extract.

Evidence for the Formation of Benzacridine Derivatives in Alkaline-Treated Sunflower Meal and Model Solutions.

Sunflower extraction meal (SEM) is an economically interesting protein source. During alkaline extraction of proteins, the presence of chlorogenic acid (CQA) in the meal gives rise to the formation of o-quinones. Reactions with nucleophiles present in proteins can lead to green discoloration. Although such reactions have been known for a long time, there is a lack of information on the chemical nature of the reaction products. SEM and model systems consisting of amino acids and CQA were subjected to alkaline treatment and, for comparison, to oxidation of CQA by polyphenoloxidase (PPO). Several green trihydroxy benzacridine (TBA) derivatives were tentatively identified in all samples by UHPLC-DAD-MS/MS. Surprisingly, in alkaline-treated samples of particular amino acids as well as in SEM, the same six TBA isomers were detected. In contrast, the enzymatically oxidized samples resulted in only three TBA derivatives. Contrary to previous findings, neither peptide nor amino acid residues were attached to the resultant benzacridine core. The results indicate that the formation of TBA derivatives is caused by the reaction between CQA quinones and free NH2 groups. Further research is necessary to elucidate the structure of the addition products for a comprehensive evaluation of food and feed safety aspects.

Effects of a quercetin-rich onion skin extract on 24 h ambulatory blood pressure and endothelial function in overweight-to-obese patients with (pre-)hypertension: a randomised double-blinded placebo-controlled cross-over trial.

The polyphenol quercetin may prevent CVD due to its antihypertensive and vasorelaxant properties. We investigated the effects of quercetin after regular intake on blood pressure (BP) in overweight-to-obese patients with pre-hypertension and stage I hypertension. In addition, the potential mechanisms responsible for the hypothesised effect of quercetin on BP were explored. Subjects (n 70) were randomised to receive 162 mg/d quercetin from onion skin extract powder or placebo in a double-blinded, placebo-controlled cross-over trial with 6-week treatment periods separated by a 6-week washout period. Before and after the intervention, ambulatory blood pressure (ABP) and office BP were measured; urine and blood samples were collected; and endothelial function was measured by EndoPAT technology. In the total group, quercetin did not significantly affect 24 h ABP parameters and office BP. In the subgroup of hypertensives, quercetin decreased 24 h systolic BP by -3·6 mmHg (P=0·022) when compared with placebo (mean treatment difference, -3·9 mmHg; P=0·049). In addition, quercetin significantly decreased day-time and night-time systolic BP in hypertensives, but without a significant effect in inter-group comparison. In the total group and also in the subgroup of hypertensives, vasoactive biomarkers including endothelin-1, soluble endothelial-derived adhesion molecules, asymmetric dimethylarginine, angiotensin-converting enzyme activity, endothelial function, parameters of oxidation, inflammation, lipid and glucose metabolism were not affected by quercetin. In conclusion, supplementation with 162 mg/d quercetin from onion skin extract lowers ABP in patients with hypertension, suggesting a cardioprotective effect of quercetin. The mechanisms responsible for the BP-lowering effect remain unclear.

Quantification of anthocyanins in elderberry and chokeberry dietary supplements.

Elderberry and chokeberry food supplements may be 'functional food' in patients with metabolic syndrome or influenza but, for this, adequate amounts of co-active ingredients must be consumed in the daily dose. This study aimed to quantify the anthocyanin content in three elderberry and six chokeberry products to assess their usefulness as functional food. Analyses were carried out using an established HPLC procedure. The minimum anthocyanin doses for the treatment of metabolic syndrome disorders were estimated as 110 mg per day and 3.5 g per day for influenza. Three products were inappropriate for clinical use. The lowest liquid supplies were achieved with a proprietary elderberry concentrate (11 mL) and a proprietary chokeberry mother juice (100 mL). Clinical studies are now required to prove the effectiveness and adapt the doses according to the clinical symptoms.

Are High Proanthocyanidins Key to Cranberry Efficacy in the Prevention of Recurrent Urinary Tract Infection?

Most research on American cranberry in the prevention of urinary tract infection (UTI) has used juices. The spectrum of components in juice is limited. This study tested whether whole cranberry fruit powder (proanthocyanidin content 0.56%) could prevent recurrent UTI in 182 women with two or more UTI episodes in the last year. Participants were randomized to a cranberry (n = 89) or a placebo group (n = 93) and received daily 500 mg of cranberry for 6 months. The number of UTI diagnoses was counted. The intent-to-treat analyses showed that in the cranberry group, the UTIs were significantly fewer [10.8% vs. 25.8%, p = 0.04, with an age-standardized 12-month UTI history (p = 0.01)]. The Kaplan-Meier survival curves showed that the cranberry group experienced a longer time to first UTI than the placebo group (p = 0.04). Biochemical parameters were normal, and there was no significant difference in urinary phenolics between the groups at baseline or on day180. The results show that cranberry fruit powder (peel, seeds, pulp) may reduce the risk of symptomatic UTI in women with a history of recurrent UTIs.

Study of Stevia rebaudiana Bertoni antioxidant activities and cellular properties.

The aim of our study was to determine the antioxidant activities, cytotoxicity and proliferative properties in Stevia rebaudiana leaves and stems. Leaves extracts exhibited a higher antioxidant activity than stems extract, through oxygen radical absorbance capacity (ORAC) and cellular antioxidant activity (CAA) assays. Stevioside and rebaudioside A, the main sweetening metabolites in stevia leaves, exhibited a low ORAC value in comparison with plant extracts, while did not elicit any CAA. Stevia rebaudiana did not exhibit toxicity against HepG2 (hepatocellular carcinoma) human cells. No proliferative nor catalase modulations were observed in cells treated with such extracts. Our findings support the promising role of stevia that, apart from its sweetness, can act as a source of antioxidants, even at the intracellular level. This activity makes S. rebaudiana crude extract an interesting resource of natural sweetness with antioxidant properties which may find numerous applications in foods and nutritional supplements industries.

Proanthocyanin content in cranberry CE medicinal products.

The CE marking is a statutory marking for certain products sold within the European Economic Area. Medicinal products with a CE label are not regulated by the European Medicines Agency but are licensed according to the directives of the European Community. We have analysed the proanthocyanin (PAC) content of four cranberry CE products by both a photometric (DMAC method using 4-dimethylamino-cinnamic-aldehyde as colouring reagent) and a high-performance liquid chromatography assay and have compared the daily dosages recommended for the products by their manufacturers with benchmark doses obtained from the literature. For all CE products, the identified DMAC values for the PAC content per unit were below those declared. For two of the CE medicinal products, not even the manufacturers' maximum daily dosages have type A PAC contents that would have any chance of providing the health benefits promised on the product information sheets; the other two might have some chance, but only at maximum dosage (nine capsules per day for one of them). CE medicinal products should be better controlled by regulatory authorities to prevent consumers from buying and taking doses that are inadequate to provide the benefits claimed.

Prevention of urinary tract infections with vaccinium products.

Cranberries exert a dose-dependent inhibition of the adherence of E. coli fimbriae to uroepithelial cells. This was demonstrated in vitro but also ex vivo in vitro with urine from cranberry consumers. The active principle has not been identified in detail but type-A proanthocyanidins (PAC) play an important role in the mechanism of action. Since the three species, American cranberry (Vaccinium macrocarpon), European cranberry (Vaccinium oxycoccus) and/or lingonberry (Vaccinium vitis-idaea), have different patterns of type-A PACs, results from one species cannot be transferred to the others. It seems likely that most of the studies with monopreparations from V. macrocarpon were underdosed. Whereas photometric PAC quantification may overestimate the true content on co-active compounds, reversed phase high-performance liquid chromatograpy may underestimate them. Recent studies with PAC doses in the upper range (DMAC method) or declared type-A PAC content in the daily dose reveal a dose-dependent trend of clinical effectiveness, however, with a possible ceiling effect. In order to clarify this, future three-arm studies should investigate Vaccinium preparations with higher type-A PAC doses than previously used. We analysed two popular European vitis-idaea products, a mother juice and a proprietary extract. Both preparations may be appropriate to confirm the Vaccinium urinary tract infection-preventive effect beyond doubt.

Quantitative evaluation of the beneficial effects in the mdx mouse of epigallocatechin gallate, an antioxidant polyphenol from green tea.

In two separate previous studies, we reported that subcutaneous (sc) or oral administration of (-)-epigallocatechin-3-gallate (EGCG) limited the development of muscle degeneration of mdx mice, a mild phenotype model for Duchenne muscular dystrophy (DMD). However, it was not possible to conclude which was the more efficient route of EGCG administration because different strains of mdx mice, periods of treatment and methods of assessment were used. In this study, we investigated which administration routes and dosages of EGCG are the most effective for limiting the onset of dystrophic lesions in the same strain of mdx mice and applying the same methods of assessment. Three-week-old mdx mice were injected sc for 5 weeks with either saline or a daily average of 3 or 6 mg/kg EGCG. For comparison, age-matched mdx mice were fed for 5 weeks with either a diet containing 0.1% EGCG or a control diet. The effects of EGCG were assessed quantitatively by determining the activities of serum muscle-derived creatine kinase, isometric contractions of triceps surae muscles, integrated spontaneous locomotor activities, and oxidative stress and fibrosis in selected muscles. Oral administration of 180 mg/kg/day EGCG in the diet was found the most effective for significantly improving several parameters associated with muscular dystrophy. However, the improvements were slightly less than those observed previously for sc injection started immediately after birth. The efficacy of EGCG for limiting the development of dystrophic muscle lesions in mice suggests that EGCG may be of benefit for DMD patients.

Simplified analysis of flavanols in matcha tea.

Matcha tea contains only the softer parts of the tea leaves and is finely ground. Therefore, extraction of the flavanols for analysis by HPLC is possible by a simpler protocol compared to the ISO 14502-2 method. 21 different simplified extraction methods were screened and five of them gave equal results as the ISO 14502-2 method. The simplest and fastest method consists of extraction by ethanol + water (7 + 3, v + v) at room temperature with ultrasonication. This method was validated by determining accuracy, intraday and interday repeatability. The simplified method was successfully applied to four traditional matcha teas and two powdered green teas from Japan. This method paves the way for time-saving, energy-saving and accurate analyses of flavanols in matcha tea.

Screening of Thymoquinone Content in Commercial Nigella sativa Products to Identify a Promising and Safe Study Medication.

(1) Background: Thymoquinone (TQ) is the leading compound accounting for the pharmacological effects of Nigella sativa seed oil, also known as black seed oil. This study aimed to analyze the TQ content of commercial black seed oils and black seed oil-containing capsules to obtain information on the quality of the products and to find a promising and safe study medication for a putative clinical study. (2) Methods: Six black seed oils and five black seed oil-containing capsules were analyzed. TQ was quantified using a validated method consisting of a simple methanolic extraction and a fast HPLC-UV analysis. (3) Results: The TQ content varied from 3.08 to 809.4 mg/100 g (mean). The highest TQ content was found in a bottled oil, which might be considered for a clinical study. A dose of 4 mL of this oil per day contains 30 mg TQ, which is unlikely to be harmful. Based on the literature, a safe daily TQ dosage appears to be <48.6 mg per adult. (4) Conclusions: These findings suggest that black seed products should be regulated regarding TQ content to enable consumers to buy black seed food supplements of known content for the maintenance and improvement of health.

Tandem mass spectrometric fragmentation patterns of known and new steviol glycosides with structure proposals.

Stevia rebaudiana contains several steviol glycosides that have a sweet flavor. They are up to 450 times sweeter than sucrose, but some have an undesirable aftertaste. Up to 2010, ten different steviol glycosides have been described from the leaves or purified extracts of S. rebaudiana. In this paper, the tandem mass spectrometric fragmentation patterns of these ten compounds are compiled, along with a scheme for structural elucidation. This scheme is then applied to 12 steviol glycosides that have not yet been described. The proposed structures of five steviol glycosides have been confirmed by other authors.

Chiral separation of (+)/(-)-catechin from sulfated and glucuronidated metabolites in human plasma after cocoa consumption.

Cocoa is well-known to be rich in flavan-3-ols. Previous analyses have established that alkaline treatment of cocoa beans results in epimerization of (-)-epicatechin to (-)-catechin and (+)-catechin to (+)-epicatechin. Now, the question is whether both epimers can be absorbed by the human organism. This paper describes sample preparation and an HPLC method for chiral determination of (+)/(-)-catechin from sulfated and glucuronidated metabolites in human plasma. The sample preparation includes enzymatic hydrolysis of the catechin metabolites, and solid-phase extraction (SPE). A PM-gamma-cyclodextrin column is used with a coulometric electrode-array detection (CEAD) system. The recovery of catechin ranges from 89.9 to 96.8%. The limit of detection is 5.9 ng mL(-1) for (-)-catechin and 6.8 ng mL(-1) for (+)-catechin, and the limit of quantification is 12.8 ng mL(-1) for (-)-catechin and 16.9 ng mL(-1) for (+)-catechin. The relative standard deviation of the method ranges from 0.9 to 1.5%. This method was successfully applied to human plasma after consumption of a cocoa drink. In one human self-experiment, (+)-catechin and (-)-catechin were found in human plasma, but metabolism of the two enantiomers differed.

Cocoa, Chocolate, and Human Health.

Cocoa has been used as a ceremonial and hedonistic food for thousands of years in the tropical parts of America and for hundreds of years in the western world. […].

Vasodilation of Tea Polyphenols Ex Vivo Is Mediated by Hydrogen Peroxide Under Rapid Compound Decay.

Improvement of endothelial function represents a major health effect of tea in humans. Ex vivo, tea and tea polyphenols stimulate nitric oxide (NO)-dependent vasodilation in isolated blood vessels. However, it was reported that polyphenols can generate reactive oxygen species (ROS) in vitro. We therefore aimed to elucidate the role of ROS production in tea polyphenol-induced vasodilation in explanted aortic rings. Vasorelaxation of rat aortic rings was assessed in an organ chamber model with low concentrations of epigallocatechin-3-gallate (EGCG), theaflavin-3,3'-digallate (TF3), and with green and black tea, with or without pretreatment with catalase or superoxide dismutase (SOD). The stability of EGCG and TF3 was measured by HPLC, and the levels of hydrogen peroxide (H2O2) were determined. EGCG and green tea-induced vasorelaxation was completely prevented by catalase and slightly increased by SOD. TF3 and black tea yielded similar results. Both EGCG and TF3 were rapidly degraded. This was associated with increasing H2O2 levels over time. Hydrogen peroxide concentrations produced in a time range compatible with tea polyphenol decay induced NO-dependent vasodilation in aortic rings. In conclusion, tea polyphenol-induced vasodilation in vitro is mediated by low levels of H2O2 generated during compound decay. The results could explain the apparent lack of vasodilatory effects of isolated tea polyphenols in humans.

Low Plasma Appearance of (+)-Catechin and (-)-Catechin Compared with Epicatechin after Consumption of Beverages Prepared from Nonalkalized or Alkalized Cocoa-A Randomized, Double-Blind Trial.

Flavan-3-ols are claimed to be responsible for the cardioprotective effects of cocoa. Alkalized cocoa powder (ALC), commonly used for many non-confectionary products, including beverages, provides less (+)-catechin, (-)-epicatechin, and procyanidins and more (-)-catechin than nonalkalized cocoa powder (NALC). This may affect the plasma appearance of monomeric flavan-3-ol stereoisomers after consumption of NALC vs. ALC. Within a randomized, crossover trial, 12 healthy nonsmokers ingested a milk-based cocoa beverage providing either NALC or ALC. Blood was collected before and within 6 h postconsumption. (+)-Catechin, (-)-catechin, and epicatechin were analyzed in plasma by HPLC as sum of free and glucuronidated metabolites. Pharmacokinetic parameters were obtained by a one-compartment model with nonlinear regression methods. For epicatechin in plasma, total area under the curve within 6 h postconsumption (AUC0-6h) and incremental AUC0-6h were additionally calculated by using the linear trapezoidal method. After consumption of NALC and ALC, (+)-catechin and (-)-catechin were mostly not detectable in plasma, in contrast to epicatechin. For epicatechin, total AUC0-6h was different between both treatments, but not incremental AUC0-6h. Most kinetic parameters were similar for both treatments, but they varied strongly between individuals. Thus, epicatechin is the main monomeric flavan-3-ol in plasma after cocoa consumption. Whether NALC should be preferred against ALC due to its higher (-)-epicatechin content remains unclear with regard to the results on incremental AUC0-6h. Future studies should investigate epicatechin metabolites in plasma for a period up to 24 h in a larger sample size, taking into account genetic polymorphisms in epicatechin metabolism and should consider all metabolites to understand inter-individual differences after cocoa intake.

Impact of a Usual Serving Size of Flavanol-Rich Cocoa Powder Ingested with a Diabetic-Suitable Meal on Postprandial Cardiometabolic Parameters in Type 2 Diabetics-A Randomized, Placebo-Controlled, Double-Blind Crossover Study.

Randomized controlled trials indicate that flavanol-rich cocoa intake may improve postprandial glucose and lipid metabolism in patients with type 2 diabetes (T2D), based on studies with meals that impose a strong metabolic load. Hence, the aim of the present study was to investigate whether flavanol-rich cocoa powder ingested as part of a diabetic-suitable meal may beneficially affect glucose, lipid metabolism, and blood pressure (BP) in patients with T2D. Twelve adults with T2D, overweight/obesity, and hypertension ingested capsules with 2.5 g of flavanol-rich cocoa or microcrystalline cellulose with a diabetic-suitable breakfast in a randomized, placebo-controlled, double-blind crossover study. BP was measured and blood samples were taken before, 2 and 4 h after breakfast and capsule intake. Cocoa treatment did not affect glucose, insulin, homeostasis model assessment for insulin resistance (HOMA-IR), triglycerides, total cholesterol, low density lipoprotein-cholesterol, high density lipoprotein-cholesterol, and BP. For glucose, insulin and HOMA-IR, only effects by time were observed after both treatments. Thus, 2.5 g of flavanol-rich cocoa powder ingested as part of a diabetic-suitable meal does not seem to affect postprandial glucose and lipid metabolism and BP in stably-treated diabetics. Nevertheless, future studies with close-meshed investigations are desirable, providing realistic amounts of cocoa together with realistic meals rich in carbohydrates to subjects with T2D or metabolic syndrome, which do not afford pharmacological treatment.

Beaming steviol glycoside analysis into the next dimension.

Nine state-of-the-art reversed phase (RP) columns for ultra-high performance liquid chromatography were tested for the separation of steviol glycosides. The main criteria were resolution of the critical peak pair rebaudioside A and stevioside and the retention time of rebaudioside D. Three columns yielded a resolution of 2 or more of the critical peak pair and two of them showed sufficient retention of rebaudioside D, namely 1.62 and 1.84min corresponding to retention factors of 0.98 and 1.24. The separation of nine steviol glycosides was possible in 11min with UV and MS compatible, buffer-free eluents at moderate temperature. The presented method is proposed to be adopted as a new official method.

Bioavailability of Quercetin from Onion Extracts after Intraruminal Application in Cows.

The aim of the present study was to investigate the bioavailability of quercetin from onion bulb (OB) and onion skin (OS) extracts in ruminants. Three non-lactating cows equipped with a permanent rumen fistula intraruminally received equimolar amounts of quercetin as either aglycone, rutin, or OB or OS extract, respectively, at a dose of 50 mg of quercetin equivalents/kg of body weight. Blood samples were drawn before and frequently within the 24 h period after application of the respective substance. Quercetin and quercetin metabolites with an intact flavonol structure (kaempferol, isorhamnetin, and tamarixetin) were analyzed in plasma samples by high-performance liquid chromatography with fluorescence detection. All quercetin sources administered resulted in a fast increase of the plasma concentrations of quercetin and total flavonols (sum of quercetin and its metabolites), followed by a rapid decline, whereby significant higher concentrations occurred with OB extract and rutin compared to quercetin aglycone and OS extract, respectively. The results clearly demonstrate a higher systemic availability of quercetin from OB extract and rutin. Taken together, OB extract with a high content of quercetin glucosides is an interesting source for the application of quercetin to ruminants.