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

Upcycling flavanol-rich Chardonnay and Pinot noir grape thinned clusters as potentially functional food ingredients in cocoa-based products

In California, over 3.4 million tons of wine grapes were crushed in 2020 while every year roughly 20% of the grape mass goes unused. Grape cluster thinning at veraison, a common agricultural practice to ensure color homogeneity in wine grapes, adds to the production costs and generates substantial on-farm loss during grapevine cultivation in which the health-promoting values of thinned clusters (unripe grapes) are usually overlooked. In particular, the health-promoting properties of flavanol monomers, specifically (+)-catechin and (-)-epicatechin, and their oligomeric procyanidins, have been extensively studied in cocoa and chocolate but not so much in grape thinned clusters in recent epidemiology studies. As part of the important agricultural by-products upcycling effort, the current study compared thinned clusters from Chardonnay and Pinot noir, two premium wine grape varieties cultivated in California, to a traditionally Dutch (alkalized) cocoa powder that has been widely used in food applications. Thinned cluster fractions from Chardonnay and Pinot noir grapes grown in the North Coast of California showed much higher concentrations of flavanol monomers and procyanidins, with 208.8-763.5 times more (+)-catechin, 3.4-19.4 times more (-)-epicatechin, and 3.8-12.3 times more procyanidins (by degree of polymerization DP 1-7) than those in the traditionally Dutch cocoa powder. These flavanol-rich thinned clusters that are also considered as plant-based natural products suggested great potential to be functional ingredients in cocoa-based products-which have been ubiquitously perceived as flavanol-rich products by consumers-to enhance their overall dietary flavanol content.

Oxidation and degradation of (epi)gallocatechin gallate (EGCG/GCG) and (epi)catechin gallate (ECG/CG) in alkali solution

The oxidative decomposition/degradation of two main tea flavanols, EGCG/GCG and ECG/CG, was studied in alkaline solution under ultrasonic-assisted thermal conditions. The study employed HPLC-ESI-ToF-MS to identify the products generated by atmospheric oxygen oxidation and various base-catalyzed reactions. Strong basic condition led to accelerated hydrolysis and oxidation of EGCG/GCG and ECG/CG and yielded gallic acid, de-galloyl flavanols and corresponding o-quinone derivatives. Meanwhile, peroxidation or base-catalyzed cleavage and rearrangement occurred extensively on C- and B-rings of flavanol and generated various simpler aldehydes or acids. Besides, a number of dimers/trimers were produced. This contribution provides empirical proof of oxidative degradation of flavanols under strong alkaline condition. Meanwhile, detailed reaction mechanisms of C-/B-ring degradation and dimerization/polymerization phenomena are proposed to help understand the structural changes of flavanols under strong alkaline conditions.

Separation of flavonoid isomers by cyclic ion mobility mass spectrometry

Analytical techniques, such as liquid chromatography coupled to mass spectrometry (LC-MS) or nuclear magnetic resonance (NMR), are widely used for characterization of complex mixtures of (isomeric) proteins, carbohydrates, lipids, and phytochemicals in food. Food can contain isomers that are challenging to separate, but can possess different reactivity and bioactivity. Catechins are the main phenolic compounds in tea; they can be present as various stereoisomers, which differ in their chemical properties. Currently, there is a lack of fast and direct methods to monitor interconversion and individual reactivity of these epimers (e.g. epicatechin (EC) and catechin (C)). In this study, cyclic ion mobility mass spectrometry (cIMS-MS) was explored as a potential tool for the separation of catechin epimers. Formation of sodium and lithium adducts enhanced IMS separation of catechin epimers, compared to deprotonation and protonation. Baseline separation of the sodium adducts of catechin epimers was achieved. Moreover, we developed a fast method for the identification and semi-quantification of cIMS-MS separated catechin epimers. With this method, it is possible to semi-quantify the ratio between EC and C (1:5 to 5:1, within 50-1200 ng mL^-1) in food samples, such as tea. Finally, the newly developed approach for cIMS-MS separation of flavonoids was demonstrated to be successful in separation of two sets of positional isomers (i.e. morin, tricetin, and quercetin; and kaempferol, fisetin, luteolin, and scutellarein). To conclude, we showed that both epimers and positional isomers of flavonoids can be separated using cIMS-MS, and established the potential of this method for challenging flavonoid separations.

Preparative Separation of Procyanidins from Cocoa Polyphenolic Extract: Comparative Study of Different Fractionation Techniques

To provide further insight into the antioxidant potential of procyanidins (PCs) from cocoa beans, PC extract was fractionated by several methodologies, including solid phase extraction, Sephadex LH-20 gel permeation, and preparative HPLC using C18 and diol stationary phases. All the isolated fractions were analyzed by UHPLC-QTOF-MS to determine their relative composition. According to our results, classical techniques allowed good separation of alkaloids, catechins, dimers, and trimers, but were inefficient for oligomeric PCs. Preparative C18-HPLC method allowed the attainment of high relative composition of fractions enriched with alkaloids, catechins, and PCs with degree of polymerization (DP) < 4. However, the best results were obtained by preparative diol-HPLC, providing a separation according to the increasing DP. According to the mass spectrometry fragmentation pattern, the nine isolated fractions (Fractions II–X) consisted of exclusively individual PCs and their corresponding isomers (same DP). In summary, an efficient, robust, and fast method using a preparative diol column for the isolation of PCs is proposed. Regarding DPPH^• and ABTS^•+ scavenging activity, it increases according to the DP; therefore, the highest activity was for cocoa extract > PCs > monomers. Thereby, cocoa procyanidins might be of interest to be used as alternative antioxidants.

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 (AUC_0–6h) and incremental AUC_0–6h 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 AUC_0–6h was different between both treatments, but not incremental AUC_0–6h. 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 AUC_0–6h. 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.

Biomarkers of food intake for cocoa and liquorice (products): a systematic review

Background

To unravel true links between diet and health, it is important that dietary exposure is accurately measured. Currently, mainly self-reporting methods (e.g. food frequency questionnaires and 24-h recalls) are used to assess food intake in epidemiological studies. However, these traditional instruments are subjective measures and contain well-known biases. Especially, estimating the intake of the group of confectionary products, such as products containing cocoa and liquorice, remains a challenge. The use biomarkers of food intake (BFIs) may provide a more objective measurement. However, an overview of current candidate biomarkers and their validity is missing for both cocoa- and liquorice-containing foods.

Objective

The purpose of the current study was to (1) identify currently described candidate BFIs for cocoa (products) and liquorice, (2) to evaluate the validity of these identified candidate BFIs and (3) to address further validation and/or identification work to be done.

Methods

This systematic review was based on a comprehensive literature search of three databases (PubMed, Scopus and ISI web of Science), to identify candidate BFIs. Via a second search step in the Human Metabolome Database (HMDB), the Food Database (FooDB) and Phenol-Explorer, the specificity of the candidate BFIs was evaluated, followed by an evaluation of the validity of the specific candidate BFIs, via pre-defined criteria.

Results

In total, 37 papers were included for cocoa and 8 papers for liquorice. For cocoa, 164 unique candidate BFIs were obtained, and for liquorice, four were identified in total. Despite the high number of identified BFIs for cocoa, none of the metabolites was specific. Therefore, the validity of these compounds was not further examined. For liquorice intake, 18-glycyrrhetinic acid (18-GA) was found to have the highest assumed validity.

Conclusions

For cocoa, specific BFIs were missing, mainly because the individual BFIs were also found in foods having a similar composition, such as tea (polyphenols) or coffee (caffeine). However, a combination of individual BFIs might lead to discriminating profiles between cocoa (products) and foods with a similar composition. Therefore, studies directly comparing the consumption of cocoa to these similar products are needed, enabling efforts to find a unique profile per product. For liquorice, we identified 18-GA as a promising BFI; however, important information on its validity is missing; thus, more research is necessary. Our findings indicate a need for more studies to determine acceptable BFIs for both cocoa and liquorice.

Sample preparation for liquid chromatographic analysis of phytochemicals in biological fluids

INTRODUCTION

Natural products have been used traditionally for the treatment and prevention of diseases for thousands of years and are nowadays consumed as dietary supplements and herbal medicine. To ensure the safe and effective use of these herbal products, information about bioavailability of active compounds in plasma or target tissues should be provided via validated analytical methods combined with appropriate sampling methods.

OBJECTIVE

To provide comprehensive and abridged information about sample preparation methods for the quantification of phytochemicals in biological samples using liquid chromatography analysis.

METHODS

Sample pre-treatment procedures used in analytical methods for in vivo pharmacokinetic studies of natural compounds or herbal medicines were reviewed. These were categorised according to the biological matrices (plasma, bile, urine, faeces and tissues) and sample clean-up processes (protein precipitation, liquid-liquid extraction and solid-phase extraction).

RESULTS

Although various kinds of sample pre-treatment methods have been developed, liquid-liquid extraction is still widely used and solid-phase extraction is becoming increasingly popular because of its efficiency for extensive clean up of complex matrix samples. However, protein precipitation is still favoured due to its simplicity.

CONCLUSION

Sample treatment for phytochemical analysis in biological fluids is an indispensable and critical step to obtain high quality results. This step could dominate the overall analytical process because both the duration of the process as well as the reliability of the data depend in large part on its efficiency. Thus, special attention should be given to the choice of a proper sample treatment method that targets analytes and their biomatrix.

Cocoa polyphenols and inflammatory markers of cardiovascular disease

Epidemiological studies have demonstrated the beneficial effect of plant-derived food intake in reducing the risk of cardiovascular disease (CVD). The potential bioactivity of cocoa and its polyphenolic components in modulating cardiovascular health is now being studied worldwide and continues to grow at a rapid pace. In fact, the high polyphenol content of cocoa is of particular interest from the nutritional and pharmacological viewpoints. Cocoa polyphenols are shown to possess a range of cardiovascular-protective properties, and can play a meaningful role through modulating different inflammatory markers involved in atherosclerosis. Accumulated evidence on related anti-inflammatory effects of cocoa polyphenols is summarized in the present review.

The effect of acute dark chocolate consumption on carbohydrate metabolism and performance during rest and exercise

Consumption of cocoa-enriched dark chocolate (DC) has been shown to alter glucose and insulin concentration during rest and exercise compared with cocoa-depleted control (CON). However, the impact of DC consumption on exercise metabolism and performance is uncertain. Therefore, we investigated carbohydrate metabolism via stable isotope tracer techniques during exercise after subjects ingested either DC or CON. Sixteen overnight-fasted male cyclists performed a single-blinded, randomized, crossover design trial, after consuming either DC or CON at 2 h prior to 2.5 h of steady-state (SS) exercise (∼45% peak oxygen uptake). This was followed by an ∼15-min time-trial (TT) and 60 min of recovery. [6,6-(2)H2]Glucose and [U-(13)C]glucose were infused during SS to assess glucose rate of appearance (Ra) and disappearance (Rd). After DC consumption, plasma (-)-glucose and insulin concentrations were significantly (p < 0.001) elevated throughout vs. CON. During SS, there was no difference in [6,6-(2)H2]glucose Ra between treatments, but towards the end of SS (last 60 min) there was a ∼16% decrease in Rd in DC vs. CON (p < 0.05). Accordingly, after DC there was an ∼18% significant decrease in plasma glucose oxidation (trial effect; p = 0.032), and an ∼15% increase in tracer-derived muscle glycogen utilization (p = 0.045) late during SS exercise. The higher blood glucose concentrations during exercise and recovery after DC consumption coincided with high concentrations of epicatechin and (or) theobromine. In summary, DC consumption altered muscle carbohydrate partitioning, between muscle glucose uptake and glycogen oxidation, but did not effect cycling TT performance.

Temperature influences epimerization and composition of flavanol monomers, dimers and trimers during cocoa bean roasting

Cocoa consumption is suggested to promote many health benefits, since cocoa is a rich source of flavanols; but amounts and profiles of flavanols depend strongly on the bean type, origin and manufacturing process. Roasting is known as a crucial step in technical treatment of cocoa, which leads to flavanol losses and modifications, especially the epimerization of (-)-epicatechin to (-)-catechin. This study monitors the influence of cocoa bean roasting on the composition of flavanol monomers to trimers, with special focus on epimerization, which was quantified for procyanidin dimers, and also observed for trimers for the first time. Five dimeric and two trimeric potential epimerization products were detected and the extent of epimerization during cocoa roasting was shown to be a function of temperature. The data also showed remarkable variations in the change of flavanol content. The quantified flavanols decreased about 50% in Java beans and increased about 30% in Ivory Coast beans, despite being roasted under equal conditions.

Bolus consumption of a specifically designed fruit juice rich in anthocyanins and ascorbic acid did not influence markers of antioxidative defense in healthy humans

Exotic fruits such as açai, camu-camu, and blackberries rich in natural antioxidants (ascorbic acid, anthocyanins) are marketed as "functional" foods supporting a pro-/antioxidant balance. Confirming data from human studies are lacking. Within a randomized controlled crossover trial, 12 healthy nonsmokers ingested 400 mL of a blended juice of these fruits or a sugar solution (control). Blood was drawn before and afterward to determine antioxidants in plasma, markers of antioxidant capacity [trolox equivalent antioxidant capacity, Folin-Ciocalteu reducing capacity, total oxidant scavenging capacity (TOSC)] and oxidative stress [isoprostane, DNA strand breaks in leukocytes in vivo], and their resistance versus H₂O₂-induced strand breaks. Compared with sugar solution, juice consumption increased plasma ascorbic acid and maintained TOSC and partly Folin-Ciocalteu reducing capacity (both P values < 0.05). Strand breaks in vivo increased after ingestion of both beverages (P < 0.001), probably due to postprandial and/or circadian effects. This anthocyanin-rich fruit juice may stabilize the pro-/antioxidant balance in healthy nonsmokers without affecting markers of oxidative stress.

Evaluation of different extraction approaches for the determination of phenolic compounds and their metabolites in plasma by nanoLC-ESI-TOF-MS

Sample preparation is an important step for the determination of phenolic compounds in biological samples. Different extraction methods have been tested to determine phenolic compounds and their metabolites in plasma by nano-liquid chromatography coupled to electrospray ionisation-time-of-flight mass spectrometry (nanoLC-ESI-TOF-MS). The sample treatment optimisation was performed using commercial foetal bovine serum spiked with representative phenolic standards, namely naringenin, luteolin, verbascoside, apigenin, rutin, syringic acid and catechin. Different protein-precipitation conditions were evaluated as well as enzymatic digestion with trypsin and solid-phase extraction using different phases such as C-18, ABN and ENV+, working at different pH values. The optimum extraction procedure consisted of a previous protein-precipitation step using HCl 200 mmol/L in methanol for 2.5 h at 50 °C followed by a solid-phase extraction using C-18 cartridges at pH 2.5. This procedure was finally applied to the plasma of rats overfed with a phenolic-rich Lippia citriodora extract. These samples were analysed by nanoLC-ESI-TOF-MS, enabling the identification of five compounds previously found in the administered L. citriodora extract and one metabolite.

Pharmacokinetics and blood-brain barrier penetration of (+)-catechin and (-)-epicatechin in rats by microdialysis sampling coupled to high-performance liquid chromatography with chemiluminescence detection

(+)-Catechin (C) and (-)-epicatechin (EC), as the basic monomer units of flavanols, can be widely found in natural products or medicinal herbs. Recent pharmacological studies have revealed that C and EC exhibit good neuroprotective effects. However, there is little information about pharmacokinetic profiles in the brain and in vivo BBB penetration of C and EC. In this paper, an ultrasensitive method using high-performance liquid chromatography (HPLC) with chemiluminescence (CL) detection was developed for the analysis of microdialysis samples. The detection limits for C and EC in Ringer's solution were 1.0 and 1.2 ng/mL, respectively. The intraday and interday accuracies for C and EC in Ringer's solution ranged from -3.0 to 4.4%, and the intraday and interday precisions were below 5.2%. The mean in vivo recoveries of C and EC in microdialysis probes were 33.7% and 26.5% in blood while 38.3% and 29.1% in brain. Pharmacokinetic parameters were estimated using the statistical moment method after iv administration (C and EC, 20 mg/kg of body weight) in rats. Brain-to-blood (AUC(brain)/AUC(blood)) distribution ratios were 0.0726 ± 0.0376 for C and 0.1065 ± 0.0531 for EC, indicating that C and EC could pass through the BBB, which is further evidence of their neuroprotective effects.

Rapid UHPLC determination of polyphenols in aqueous infusions of Salvia officinalis L. (sage tea)

Sage tea, the aqueous infusion of dried sage leaves (Salvia officinalis L.), is used as a form of food as well as a form of traditional herbal medicine. Several in vivo and in vitro studies point to sage polyphenols as active principles that may inhibit lipid peroxidation and improve antioxidant defences. This study describes an UHPLC methodology with MS/MS and UV detection, which allows the separation, identification and quantification of the major phenolic constituents in sage tea within 34 min, and was used to characterize 16 commercial brands of sage tea.The quantitatively dominating compounds were either rosmarinic acid (12.2–296 mg/l) or luteolin-7-o-glucuronide (37.9–166 mg/l) [corrected].In general, considerable differences in polyphenolic composition between the brands were detected, leading to the demand for quality standardization and control, especially if these sage teas are to be used for therapeutic purposes.

Recommending flavanols and procyanidins for cardiovascular health: current knowledge and future needs

Data on the potential health benefits of dietary flavanols and procyanidins, especially in the context of cardiovascular health, are considerable and continue to accumulate. Significant progress has been made in flavanol analytics and the creation of phytonutrient-content food databases, and novel data emanated from epidemiological investigations as well as dietary intervention studies. However, a comprehensive understanding of the pharmacological properties of flavanols and procyanidins, including their precise mechanisms of action in vivo, and a conclusive, consensus-based accreditation of a causal relationship between intake and health benefits in the context of primary and secondary cardiovascular disease prevention is still outstanding. Thus, the objective of this review is to identify and discuss key questions and gaps that will need to be addressed in order to conclusively demonstrate whether or not dietary flavanols and procyanidins have a role in preventing, delaying the onset of, or treating cardiovascular diseases, and thus improving human life expectancy and quality of life.