Analysis of procyanidins in chocolate by reversed-phase high-performance liquid chromatography with electrospray ionisation mass spectrometric and tandem mass spectrometric detection

Study on the extraction, purification, stability, free radical scavenging kinetics, polymerization degree and characterization of proanthocyanidins from Pinus koraiensis seed scales

To efficiently harness resources from Pinus koraiensis seed scales, a type of forestry waste, rigorous studies on the extraction, purification, stability, and free radical scavenging capacity of the proanthocyanidins derived from these seed scales were conducted. Kinetic models showed that under ultrasonic conditions, the proanthocyanidins content reached 2.66 mg/g within 0.5 h. The optimal storage parameters include darkness, 4 °C, and pH 4. The degrees of polymerization of the mixture and the high- and low-polymer components were 4.89, 7.42 and 3.07, respectively, with the low-polymer component exhibiting the highest radical scavenging activity. Through HPLC-QE-MS/MS, 1H NMR, and FT-IR analyses, we identified proanthocyanidin B1, proanthocyanidin B2, (-)-epicatechin, and polymeric trimer esters. The Pinus koraiensis proanthocyanidins exhibited a high molecular weight, a complex internal molecular structure, and commendable stability, with crystallization requiring elevated temperatures. Therefore, the proanthocyanidins from Pinus koraiensis seed scales have emerged as highly promising novel natural antioxidants.

Development and application of mass spectrometric molecular networking for analyzing the ingredients of areca nut

Areca nut (Areca catechu L.) is commonly consumed as a chewing food in the Asian region. However, the investigations into the components of areca nut are limited. In this study, we have developed an approach that combines mass spectrometry with feature-based molecular network to explore the chemical characteristics of the areca nut. In comparison to the conventional method, this technique demonstrates a superior capability in annotating unknown compounds present in areca nut. We annotated a total of 52 compounds, including one potential previously unreported alkaloid, one carbohydrate, and one phenol and confirmed the presence of 7 of them by comparing with commercial standards. The validated method was used to evaluate chemical features of areca nut at different growth stages, annotating 25 compounds as potential biomarkers for distinguishing areca nut growth stages. Therefore, this approach offers a rapid and accurate method for the component analysis of areca nut.

Rapidly analyzing of ingredients during chewing and processing of areca nut using feature-based molecular networking

As a traditional herbal medicine and food in China and many other Asian countries, the areca nut (Areca catechu L.) is not only widely used for the treatment of various diseases, but also popular as a chewing hobby. However, as a first-class carcinogen designated by IARC, clinical studies have shown that long-term chewing of areca nut is associated with oral mucosal diseases and even oral cancer. Moreover, the incidence of these diseases varies regionally, suggesting that it may be related to edible methods in different regions. In this study, UPLC-Q-TOF-MSE was combined with feature-based molecular networking to systematically characterise the chemical ingredients of areca nut. Based on these results, the ingredients of different edible parts and edible methods was rapidly compared. The compositional changes during the production process were also analysed. The obtained results provide a foundation for the scientific utilisation of areca nut.

Shades of Fine Dark Chocolate Colors: Polyphenol Metabolomics and Molecular Networking to Enlighten the Brown from the Black

High-quality dark chocolates (70% cocoa content) can have shades from light to dark brown color. This work aimed at revealing compounds that discriminate black and brown chocolates. From 37 fine chocolate samples from years 2019 and 2020 provided by Valrhona,8 dark black samples and 8 light brown samples were selected. A non-targeted metabolomics study was performed based on ultra-high performance liquid chromatography-high resolution mass spectrometry/mass spectrometry experiments, univariate, multivariate, and feature-based molecular networking analyses. Twenty-seven overaccumulated discriminating compounds were found for black chocolates. Among them, glycosylated flavanols including monomers and glycosylated A-type procyanidin dimers and trimers were highly representative. Fifty overaccumulated discriminating compounds were found for brown chocolates. Most of them were B-type procyanidins (from trimers to nonamers). These phenolic compounds may be partially related to the chocolate colors as precursors of colored compounds. This study increases the knowledge on the chemical diversity of dark chocolates by providing new information about the phenolic profiles of black and brown chocolates.

UHPLC-Q-Orbitrap /MS2 identification of (+)-Catechin oxidation reaction dimeric products in red wines and grape seed extracts

B-type procyanidin dimers and (+)-catechin dimeric oxidation products were analyzed in grape seed extracts and red wines (UHPLC-Q-Orbitrap MS). The different dimers had different fragmentation patterns according to their interflavan linkage position. Oxidation dimeric compounds had a specific fragment ion at m/z 393, missing for B-Type dimers fragmentations. A fragment ion at m/z 291 occurred and was specific for oxidation dimeric compounds with a COC linkage. Higher level oxidation products had abundant specific fragments: m/z 425, 397 and 245. These fragmentations were useful to identify them in complex samples such as grape seed extracts and wines. Three grape varieties and three ripening stages were selected and the corresponding seed extracts were obtained. The analyses revealed an increasing trend for the oxidation markers during grape ripening. The analysis of Syrah wines (2018, 2014, 2010) showed a decreasing trend of these molecules during wine ageing which might be due to further oxidation.

Aqueous Extract of Cocoa Phenolic Compounds Protects Differentiated Neuroblastoma SH-SY5Y Cells from Oxidative Stress

Cocoa is a rich source of polyphenols, especially flavanols and procyanidin oligomers, with antioxidant properties, providing protection against oxidation and nitration. Cocoa phenolic compounds are usually extracted with methanol/ethanol solvents in order to obtain most of their bioactive compounds; however, aqueous extraction seems more representative of the physiological conditions. In this study, an aqueous extract of cocoa powder has been prepared and chemically characterized, and its potential protective effect against chemically-induced oxidative stress has been tested in differentiated human neuroblastoma SH-SY5Y cells. Neuronal-like cultured cells were pretreated with realistic concentrations of cocoa extract and its major monomeric flavanol component, epicatechin, and then submitted to oxidative stress induced by a potent pro-oxidant. After one hour, production of reactive oxygen species was evaluated by two different methods, flow cytometry and in situ fluorescence by a microplate reader. Simultaneously, reduced glutathione and antioxidant defense enzymes glutathione peroxidase and glutathione reductase were determined and the results used for a comparative analysis of both ROS (reactive oxygen species) methods and to test the chemo-protective effect of the bioactive products on neuronal-like cells. The results of this approach, never tested before, validate both analysis of ROS and indicate that concentrations of an aqueous extract of cocoa phenolics and epicatechin within a physiological range confer a significant protection against oxidative insult to neuronal-like cells in culture.

A Study of Catechin Photostability Using Photolytic Processing

Catechin exhibits numerous physiological characteristics. In this study, we determined the photosensitivity of catechin to various lights under alkaline conditions, and the mechanisms by which catechin generates free radical species and polymerizes via a photoreaction. In addition to this, the application of catechin photolysis was investigated. A solution of catechin is transparent, but turns yellowish under blue light illumination (BLI) in neutral or weak alkaline solutions. When catechin is subjected to BLI, a dimeric catechin (proanthocyanidin) and a superoxide anion radical (O2•−) are generated in a photolytic reaction. When ascorbic acid or gallic acid is added to catechin and the mixture is subjected to BLI at alkaline pH, fewer catechin dimers and less O2•− are produced, because both acids inhibit the photosensitive oxidation of catechin. When AlCl3 is added to catechin and the mixture is subjected to BLI at pH 8, a photolytic reaction is suppressed by AlCl3, and AlCl3 acts as a catalyst for the disconnection of proanthocyanidin during photolysis. Under alkaline conditions, catechin generates O2•− via photosensitive oxidation, which suppresses the growth of Acinetobacter baumannii (A. baumannii) by at least 4 logs, and deactivates its multi-drug-resistant strain. This study shows that catechin photolysis is a process of oxidation, and that it can be safely applied as a tool for environmental applications.

Metabolites profiling of date palm (Phoenix dactylifera L.) commercial by-products (pits and pollen) in relation to its antioxidant effect: a multiplex approach of MS and NMR metabolomics

INTRODUCTION

Phoenix dactylifera L. (date palm) is one of the most valued crops worldwide for its economical and nutraceutical applications of its date fruit (pericarp). Currently date pits, considered as a waste product, is employed as coffee substitute post roasting. Whereas, pollen represents another valuable by-product used as a dietary supplement.

OBJECTIVES

In this study, a large-scale comparative metabolomics approach was performed for the first characterization and standardization of date palm by-products viz., date pits and pollen. Moreover, roasting impact on date pit metabolite composition was also assessed.

METHODS

Metabolites profiling of pits and pollen was determined via a multiplex approach of UPLC-MS and NMR, coupled to multivariate analysis, in relation to its antioxidant activities.

RESULTS

Chemical analyses led to the identification of 67 metabolites viz., phenolic acids, flavonols, fatty acids, sphingolipids, steroids and saponins of which 10 are first time to be reported. The enrichment of steroids in date pollen accounts for its fertility promoting properties, whereas date pit was found a rich source for antioxidant polyphenols using metabolomics.

Bioactive Compounds from Theobroma cacao: Effect of Isolation and Safety Evaluation

Plants, including most food and feed plants, produce a broad range of bioactive chemical compounds. Among these compounds, polyphenols are reported to provide beneficial effects as anti-carcinogenic, anti-atherogenic, anti-inflammatory, immune modulating, anti-microbial, vasodilatory and analgesic. Cocoa (Theobroma cacao), a major, economically important, international crop, has been related to several nutritional benefits, which have been associated with the phenolic fraction. The main subclass of flavonoids found in cocoa is flavanols, particularly (epi)catechins monomers, and their oligomers, also known as procyanidins. In this study, these compounds were isolated by different methodologies as solid phase extraction (SPE), semi-preparative high-performance liquid chromatography (HPLC) and membrane technologies to obtain different polyphenolic profiles by HPLC coupled to electrospray time-of-flight mass spectrometry (ESI-TOF-MS) and to test their cytotoxicity. Finally, different polyphenolic profiles were collected, where the combination of both semi-preparative HPLC and SPE technologies provided the most purified fractions. Filtration with membranes and SPE provide extracts with different composition depending on the pore size of membranes and on the solvent, respectively. In addition, the results of toxicity assay indicated low levels in all fractions.

Lotus seed skin proanthocyanidin extract exhibits potent antioxidant property via activation of the Nrf2-ARE pathway

Lotus seed is well known as traditional food and medicine, but its skin is usually discarded. Recent studies have shown that lotus seed skin contains a high concentration of proanthocyanidins that have multi-functions, such as antioxidation, anti-inflammation, and anti-cancer effects. In the present study, we aimed to isolate and purify the proanthocyanidins from lotus seed skin by acetone extraction and rotary evaporation, identify their chemical structures by HPLC-MS-MS and NMR, and further investigate the antioxidant properties of the extract purified by macroporous resin (PMR) from lotus seed skin both in vitro and in vivo. The results showed that PMR mainly contained oligomeric proanthocyanidins, especially dimeric procyanidin B1 (PB1), procyanidin B2 and procyanidin B4. Although it had limited ability to directly scavenge radicals in vitro, PMR could significantly enhance the expressions of antioxidant proteins via activation of nuclear factor-E2-related factor 2 (Nrf2)-antioxidant response element (ARE) pathway in HepG2 cells. Molecular data revealed that PB1, a major component in PMR, stabilized Nrf2 by inhibiting the ubiquitination of Nrf2, which led to subsequent activation of the Nrf2-ARE pathway, including the enhancements of Nrf2 nuclear translocation, Nrf2-ARE binding and ARE transcriptional activity. Moreover, the in vivo results in high fat diet-induced mice further verified the powerful antioxidant property of PMR. These results revealed that lotus seed skin is a promising resource for functional food development.

Procyanidins: a comprehensive review encompassing structure elucidation via mass spectrometry

Procyanidins are polyphenols abundant in dietary fruits, vegetables, nuts, legumes, and grains with a variety of chemopreventive biological effects. Rapid structure determination of these compounds is needed, notably for the more complex polymeric procyanidins. We review the recent developments in the structure elucidation of procyanidins with a focus on mass spectrometric approaches, especially liquid chromatography-tandem mass spectrometry (LC-MS/MS) and matrix-assisted laser desorption ionization (MALDI) MS/MS.

Origin-based polyphenolic fingerprinting of Theobroma cacao in unfermented and fermented beans

A comprehensive analysis of cocoa polyphenols from unfermented and fermented cocoa beans from a wide range of geographic origins was carried out to catalogue systematic differences based on their origin as well as fermentation status. This study identifies previously unknown compounds with the goal to ascertain, which of these are responsible for the largest differences between bean types. UHPLC coupled with ultra-high resolution time-of-flight mass spectrometry was employed to identify and relatively quantify various oligomeric proanthocyanidins and their glycosides amongst several other unreported compounds. A series of biomarkers allowing a clear distinction between unfermented and fermented cocoa beans and for beans of different origins were identified. The large sample set employed allowed comparison of statistically significant variations of key cocoa constituents.

Phenolic compounds profile and antioxidant properties of six sweet cherry (Prunus avium) cultivars

Sweet cherry (Prunus avium) fruits are a nutritionally important food rich in dietary phenolic compounds. The aim of this study was to investigate the phenolic profile and chemometric discrimination of fruits from six cherry cultivars using a quantitative metabolomics approach, which combine non-targeted mass spectrometry and chemometric analysis. The assessment of the phenolic fingerprint of cherries allowed the tentative identification of 86 compounds. A total of 40 chlorogenic acids were identified in cherry fruit, which pointed out hydroxycinnamic acid derivatives as the main class of phenolics by number of compounds. Among the compounds detected, 40 have been reported for the first time in sweet cherry fruit. Hydroxycinnamic acids are also the quantitatively most represented class of phenolic compounds in the cherry cultivars with the exception of Lapins and Durone della Marca where the most representative class of phenolic compounds were anthocyanins and flavan-3-ols, respectively. This non-targeted approach allowed the tentative identification of the cultivar-compound relationships of these six cherry cultivars. Both anthocyanins and colorless phenolic compounds profile appeared to be cultivar-dependent. In detail, anthocyanins and flavonols patterns have the potential to be used for the determination of a varietal assignment of cherries.

Photo-catalytic polymerization of catechin molecules in alkaline aqueous

Polyphenols are associated with a wide range of physiological properties. Catechin is a flavan-3-ol with five phenolic hydroxyl groups. After blue light illumination, the transparent solution of catechin became yellowish. The effects of visible light illumination (400-800nm) were investigated on molecular structures and antioxidant capacities of catechin. Under the neutral or alkaline aqueous with the illumination of blue light, the photolysis and polymerization of catechin were observed in this study. A chromogenic catechin dimer was separated and identified as a proanthocyanidin by the chromatographic technique and mass spectrometry. For quantitative evaluation, the signal intensities of the catechin and the photochemical product show a negative correlation in the liquid chromatograms. The oligomer of flavan-3-ols (catechin dimer) is suggested as a dimeric B type proanthocyanidin, which has the molecular formula C₃₀H₂₆O₁₂ and 578.14g/mol in exact mass. The mass spectrum of catechin dimer had characteristic ion signals in m/z 577, 560, 439Da. However, the total phenolic contents and scavenging O₂^- activity of catechin treated by blue light illumination are not changed significantly at the neutral or alkaline aqueous. Our results of photocatalytic oligomers of catechin provide a novel way to explain the sensory changes of green tea and a biochemical mechanism under the irradiation environments.

Improving the estimation of flavonoid intake for study of health outcomes

Imprecision in estimating intakes of non-nutrient bioactive compounds such as flavonoids is a challenge in epidemiologic studies of health outcomes. The sources of this imprecision, using flavonoids as an example, include the variability of bioactive compounds in foods due to differences in growing conditions and processing, the challenges in laboratory quantification of flavonoids in foods, the incompleteness of flavonoid food composition tables, and the lack of adequate dietary assessment instruments. Steps to improve databases of bioactive compounds and to increase the accuracy and precision of the estimation of bioactive compound intakes in studies of health benefits and outcomes are suggested.

Effect of cocoa products and flavanols on platelet aggregation in humans: a systematic review

The percentage of healthy subjects with decreased platelet aggregation after bolus consumption of cocoa products is reported.

UHPLC-PDA-ESI/HRMSn profiling method to identify and quantify oligomeric proanthocyanidins in plant products

Oligomeric proanthocyanidins were successfully identified by UHPLC-PDA-HRMS(n) in a selection of plant-derived materials (jujube fruit, Fuji apple, fruit pericarps of litchi and mangosteen, dark chocolate, and grape seed and cranberry extracts). The identities of 247 proanthocyanidins were theoretically predicted by computing high-accuracy masses based on the degree of polymerization, flavan-3-ol components, and the number of A type linkages and galloyls. MS(n) fragments allowed characterization on flavan-3-ol based on the monomer, connectivity, and location of A-type bonds. Identification of doubly or triply charged ions of 50 PAs was made on the basis of theoretical calculations. A single catechin standard and molar relative response factors (MRRFs) were used to quantify the well-separated PAs. The ratios of the SIM peak counts were used to quantify each of the unseparated isomers. This is the first report of direct determination of each of the proanthocyanidins in plant-derived foods and proanthocyanidins containing an epifisetinidol unit in grape seeds.

HPLC-DAD and HPLC-ESI-MS analyses of Tiliae flos and its preparations

In the present study extensive HPLC-DAD, HPLC-ESI-MS and NMR analyses were undertaken in the aqueous preparations (decoctions, infusions) and tinctures of Tilia platyphyllos Scop inflorescences. The aim of this work was to examine in depth the qualitative and quantitative profile of the investigated preparations, which find until today wide applications in pharmaceutical and cosmetic industry, and to propose a validated method for their quality control. An HPLC-DAD-ESI-MS method was developed and optimised for the quantitative determination of the constituents. Marker constituents of Tiliae flos are the flavonoids, while the volatile content is also used for the quality control. However, the analyses of the non-volatile fraction gave complex chromatographic fingerprints containing simple phenolics and low molecular weight procyanidins. The use of different HPLC columns permitted a good separation of the constituents and enabled their quantitation, while HPLC-MS analyses permitted the detection of procyanidin oligomers. Overall, 31 constituents were detected and identified. Extensive preparative chromatographic investigations and 2D-NMR analyses allowed the characterisation of procyanidins as epicatechin derivatives. Finally, the HPLC method was validated and complied with ICH guidelines. This is the first report of detailed analysis of the chemical composition of Tiliae flos.

Mechanisms for food polyphenols to ameliorate insulin resistance and endothelial dysfunction: therapeutic implications for diabetes and its cardiovascular complications

The rising epidemic of diabetes is a pressing issue in clinical medicine worldwide from both healthcare and economic perspectives. This is fueled by overwhelming increases in the incidence and prevalence of obesity. Obesity and diabetes are characterized by both insulin resistance and endothelial dysfunction that lead to substantial increases in cardiovascular morbidity and mortality. Reciprocal relationships between insulin resistance and endothelial dysfunction tightly link metabolic diseases including obesity and diabetes with their cardiovascular complications. Therefore, therapeutic approaches that target either insulin resistance or endothelial dysfunction alone are likely to simultaneously improve both metabolic and cardiovascular pathophysiology and disease outcomes. Moreover, combination therapies with agents targeting distinct mechanisms are likely to have additive or synergistic benefits. Conventional therapies for diabetes and its cardiovascular complications that are both safe and effective are insufficient to meet rising demand. Large, robust, epidemiologic studies demonstrate beneficial metabolic and cardiovascular health effects for many functional foods containing various polyphenols. However, precise molecular mechanisms of action for food polyphenols are largely unknown. Moreover, translation of these insights into effective clinical therapies has not been fully realized. Nevertheless, some functional foods are likely sources for safe and effective therapies and preventative strategies for metabolic diseases and their cardiovascular complications. In this review, we emphasize recent progress in elucidating molecular, cellular, and physiological actions of polyphenols from green tea (EGCG), cocoa (ECG), and citrus fruits (hesperedin) that are related to improving metabolic and cardiovascular pathophysiology. We also discuss a rigorous comprehensive approach to studying functional foods that is essential for developing novel, effective, and safe medications derived from functional foods that will complement existing conventional drugs.

Modulation of metabolic syndrome-related inflammation by cocoa

Cocoa (Theobroma cacao L., Sterculiaceae) is a widely consumed food ingredient. Although typically found in high-fat, high-sugar foods such as chocolate, cocoa is rich in polyphenols, methylxanthines, and monounsaturated fatty acids. There is increasing evidence that moderate consumption of cocoa and cocoa-containing foods may have beneficial effects on the health including vasodilatory, antioxidant, and anti-inflammatory effects. Polyphenols in cocoa, including monomeric flavanols, as well as polymeric proanthocyanidins, may play a role in these observed beneficial effects. Chronic inflammation represents a potential mechanistic link between obesity and its related pathologies: insulin resistance, dyslipidemia, and hypertension, which comprise the metabolic syndrome. In the present review, we discuss the available data regarding the modulation of metabolic syndrome-related inflammation by cocoa and cocoa-derived compounds. We emphasize studies using laboratory animals or human subjects since such studies often represent the strongest available evidence for biological effects. In vitro studies are included to provide some mechanistic context, but are critically interpreted. Although the available data seem to support the anti-inflammatory effects of cocoa, further studies are needed with regard to the dose-response relationship as well as the underlying mechanisms of action. We hope this review will stimulate further research on cocoa and its anti-inflammatory activities.

Detailed polyphenol and tannin composition and its variability in Tunisian dates (Phoenix dactylifera L.) at different maturity stages

The polyphenol profile of two Tunisian varieties of dates including flavanols, flavonols, flavones, and hydroxycinnamates was characterized. Three tissue zones (flesh, peel, and stone) and three maturity stages were considered. Phenolic compounds were analyzed using reversed phase high-performance liquid chromatography coupled to UV-visible and electrospray mass spectrometry. Procyanidin oligomers and polymers were characterized and quantified using phloroglucinolysis prior to HPLC analysis. Procyanidin polymers based on (-)-epicatechin structure were by far the most concentrated polyphenols in ripe dates, accounting for 95% of total polyphenols with an average concentration of 14 g/kg in the fresh edible parts of the fruit. Interestingly, procyanidins were also highly concentrated in the stones. The concentration and average degree of polymerization (DPn) of the procyanidins decreased according to maturity. Other phenolics, including caffeoylshikimic acid hexoside, caffeoyl-sinapoyl monohexoside and dihexoside, and acetylated flavonols, were tentatively identified for the first time in the fruit.

Antihypertensive role of polyphenols

Hypertension is considered the most important risk factor in the development of cardiovascular disease. Considerable evidence suggests that oxidative stress, which results in an excessive generation of reactive oxygen species (ROS), plays a key role in the pathogenesis of hypertension. This phenomenon leads to endothelial dysfunction, an imbalance between endothelium-derived relaxing factors, such as nitric oxide (NO), and contracting factors, such as angiotensin-II and endothelin (ET)-1, favoring the latter. Vascular remodeling also takes place; both processes lead to hypertension establishment. Antioxidant therapies have been evaluated in order to decrease ROS production or increase their scavenging. In this line, polyphenols, widespread antioxidants in fruits, vegetables, and wine, have demonstrated their beneficial role in prevention and therapy of hypertension, by acting as free radical scavengers, metal chelators, and in enzyme modulation and expression. Polyphenols activate and enhance endothelial nitric oxide synthase (eNOS) expression by several signaling pathways, increase glutathione (GSH), and inhibit ROS-producing enzymes such as NADPH and xanthine oxidases. These pathways lead to improved endothelial function, subsequent normalization of vascular tone, and an overall antihypertensive effect. In practice, diets as Mediterranean and the "French paradox" phenomenon, the light and moderate red wine consumption, supplementation with polyphenols as resveratrol or quercetin, and also experimental and clinical trials applying the mentioned have coincided in the antihypertensive effect of polyphenols, either in prevention or in therapy. However, further trials are yet needed to fully assess the molecular mechanisms of action and the appearance of adverse reactions, if a more extensive recommendation of polyphenol introduction in diet wants to be made.

Flavonoid deactivation of excited state flavins: reaction monitoring by mass spectrometry

Flavin mononucleotide (FMN, as a B(2) vitamin model) was shown to induce dimerization of flavonoids (flavanone, apigenin, naringenin, eriodictyol, taxifolin, catechin, kaempferol, luteolin, quercetin, rutin, and seven smaller model phenols studied) as the major photoreaction, when aqueous solutions were exposed to visible light using a new, real-time electrospray ionization mass-spectrometric (ESI-MS) technique supported by LC-MS and MS(2) analysis. Electrophilic intermediates such as transient radical cations, o-quinones, and p-quinone methide were proposed to be involved in the coupling process. The C(3)-OH in flavon-3-ols gave rise to atypical compounds such as a depside or a dioxane-linked dimer. Flavonoid dimers, formed in vegetal extracts added to food during storage in light and for which structures are proprosed based on MS and MS(2), may affect colloidal stability, color, astringency, and antioxidative capacity.

Characterization of cocoa liquors by GC-MS and LC-MS/MS: focus on alkylpyrazines and flavanols

Flavor is one of the most important characteristics of chocolate products and is due to a complex volatile fraction, depending both on the cocoa bean genotype and the several processes occurring during chocolate production (fermentation, drying, roasting and conching). Alkylpyrazines are among the most studied volatiles, being one of the main classes of odorant compounds in cocoa products. In this work, a mass spectrometric approach was used for the comparison of cocoa liquors from different countries. A headspace solid-phase microextraction gas chromatography-mass spectrometry method was developed for the qualitative study of the volatile fraction; the standard addition method was then used for the quantitative determination of five pyrazines (2-methylpyrazine, 2,3-dimethylpyrazine, 2,5-dimethylpyrazine, 2,3,5-trimethylpyrazine and tetramethylpyrazine). Satisfactory figures of merit were obtained: Limits of quantitation were in the range 0.1-2.7 ng/g; repeatability and reproducibility varied between 3% and 7% and between 8% and 14%, respectively. The total content of the pyrazines was remarkably different in the considered samples, ranging from 99 to 708 ng/g. Tetramethylpyrazine showed the highest concentration in all samples, with a maximum value of 585 ng/g. A preliminary study was also performed on the nonvolatile fraction using LC-MS/MS, identifying some flavanols such as catechin, epicatechin and procyanidins.

Evolution of phenolic compounds from color and flavor problems to health benefits

Early studies focused on the negative effects on color and flavor of foods, followed by exploration of the antioxidant properties and the associated health benefits. The growing body of evidence suggests that plant-based polyphenols may help prevent or delay the onset of a multiplicity of diseases. Newer work suggests that a variety of polyphenols can alter the expression of genes in the inflammatory pathway. Data also show that the absorption of the polyphenols is very limited. Insulin resistance and endothelial and mitochondrial dysfunction are hallmarks of the metabolic syndrome and aging and occur at the early stages of the disease. There is limited clinical evidence that certain polyphenolic metabolites by virtue of their anti-inflammatory activities can improve insulin sensitivity and endothelial and mitochondrial function, suggesting that polyphenols are good for disease prevention. The goal of this review is to summarize the evolution and emphasize the potential benefits of polyphenols.

Inhibition of key digestive enzymes by cocoa extracts and procyanidins

This study determined the in vitro inhibitory effects of cocoa extracts and procyanidins against pancreatic α-amylase (PA), pancreatic lipase (PL), and secreted phospholipase A(2) (PLA(2)) and characterized the kinetics of such inhibition. Lavado, regular, and Dutch-processed cocoa extracts as well as cocoa procyanidins (degree of polymerization (DP) = 2-10) were examined. Cocoa extracts and procyanidins dose-dependently inhibited PA, PL, and PLA(2). Lavado cocoa extract was the most potent inhibitor (IC(50) = 8.5-47 μg/mL). An inverse correlation between log IC(50) and DP (R(2) > 0.93) was observed. Kinetic analysis suggested that regular cocoa extract, the pentamer, and decamer inhibited PL activity in a mixed mode. The pentamer and decamer noncompetitively inhibited PLA(2) activity, whereas regular cocoa extract inhibited PLA(2) competitively. This study demonstrates that cocoa polyphenols can inhibit digestive enzymes in vitro and may, in conjunction with a low-calorie diet, play a role in body weight management.

Polyphenol identification based on systematic and robust high-resolution accurate mass spectrometry fragmentation

High-mass resolution multi-stage mass spectrometry (MS(n)) fragmentation was tested for differentiation and identification of metabolites, using a series of 121 polyphenolic molecules. The MS(n) fragmentation approach is based on the systematic breakdown of compounds, forming a so-called spectral tree. A chip-based nanoelectrospray ionization source was used combined with an ion-trap, providing reproducible fragmentation, and accurate mass read-out in an Orbitrap Fourier transform (FT) MS enabling rapid assignment of elemental formulas to the molecular ions and all fragment ions derived thereof. The used protocol resulted in reproducible MS(n) fragmentation trees up to MS(5). Obtained results were stable over a 5 month time period, a concentration change of 100-fold, and small changes in normalized collision energy, which is key to metabolite annotation and helpful in structure and substructure elucidation. Differences in the hydroxylation and methoxylation patterns of polyphenolic core structures were found to be reflected by the differential fragmentation of the entire molecule, while variation in a glycosylation site displayed reproducible differences in the relative intensities of fragments originating from the same aglycone fragment ion. Accurate MS(n)-based spectral tree data are therefore a powerful tool to distinguish metabolites with similar elemental formula, thereby assisting compound identification in complex biological samples such as crude plant extracts.

Preparation of dimeric procyanidins B1, B2, B5, and B7 from a polymeric procyanidin fraction of black chokeberry ( Aronia melanocarpa )

A semisynthetic approach has been used for the preparative formation of dimeric procyanidins B1, B2, B5, and B7. As starting material for the semisynthesis, polymeric procyanidins from black chokeberry were applied. These polymers were found to consist almost exclusively of (-)-epicatechin units. Under acidic conditions the interflavanoid linkages of the polymeric procyanidins are cleaved and the liberated (-)-epicatechin can react with nucleophiles, such as (+)-catechin or (-)-epicatechin. In this way, the polymeric procyanidins are degraded while dimeric procyanidins are formed. During this reaction only dimeric procyanidins are formed that contain (-)-epicatechin in the upper unit, that is, B1 [(-)-EC-4beta-->8-(+)-C)], B2 [(-)-EC-4beta-->8-(-)-EC], B5 [(-)-EC-4beta-->6-(-)-EC], and B7 [(-)-EC-4beta-->6-(+)-C]. The reaction mixtures of the semisynthesis can be successfully fractionated with high-speed countercurrent chromatography (HSCCC), and it is possible to isolate pure procyanidins B1, B2, B5, and B7 on a preparative scale.

Off-line comprehensive 2-dimensional hydrophilic interaction x reversed phase liquid chromatography analysis of procyanidins

The development of an off-line comprehensive 2-dimensional liquid chromatography (2-D-LC) method for the analysis of procyanidins is reported. In the first dimension, oligomeric procyanidins were separated according to molecular weight by hydrophilic interaction chromatography (HILIC), while reversed phase LC was employed in the second dimension to separate oligomers based on hydrophobicity. Fluorescence, UV and electrospray ionisation mass spectrometry (ESI-MS) were employed for identification purposes. The combination of these orthogonal separation methods is shown to represent a significant improvement compared to 1-dimensional methods for the analysis of complex high molecular weight procyanidin fractions, by simultaneously providing isomeric and molecular weight information. The low correlation (r(2)<0.2100) between the two LC modes afforded a practical peak capacity in excess of 2300 for the optimal off-line method. The applicability of the method is demonstrated for the analysis of phenolic extracts of apple and cocoa.

Cocoa consumption for 2 wk enhances insulin-mediated vasodilatation without improving blood pressure or insulin resistance in essential hypertension

BACKGROUND

Essential hypertension is characterized by reciprocal relations between endothelial dysfunction and insulin resistance. Cocoa flavanols stimulate production of the vasodilator nitric oxide from vascular endothelium.

OBJECTIVE

The objective was to test the hypothesis that consumption of cocoa may simultaneously lower blood pressure, improve endothelial dysfunction, and ameliorate insulin resistance in subjects with essential hypertension.

DESIGN

We conducted a randomized, placebo-controlled, double-blind, crossover trial of a flavanol-rich cocoa drink (150 mL twice a day, approximately 900 mg flavanols/d) in individuals with essential hypertension (n = 20). Antihypertensive medications were discontinued before study enrollment. After a 7-d cocoa-free run-in period, cocoa or flavanol-poor placebo (approximately 28 mg flavanols/d) treatment for 2 wk was followed by a 1-wk washout and then crossover to the other treatment arm. Blood pressure was measured thrice weekly. At baseline and after each treatment period, we assessed insulin sensitivity (hyperinsulinemic-isoglycemic glucose clamp) and insulin-stimulated changes in brachial artery diameter and forearm skeletal muscle capillary recruitment (Doppler ultrasound with or without microbubble contrast).

RESULTS

Cocoa treatment for 2 wk increased insulin-stimulated changes in brachial artery diameter when compared with placebo [median percentage increase from baseline (25th-75th percentile): 8.3 (4.2-11.3) compared with 5.9 (-0.3 to 9.6); P < 0.04]. Nevertheless, cocoa treatment did not significantly reduce blood pressure or improve insulin resistance and had no significant effects on skeletal muscle capillary recruitment, circulating plasma concentrations of adipocytokines, or endothelial adhesion molecules.

CONCLUSIONS

Daily consumption of flavanol-rich cocoa for 2 wk is not sufficient to reduce blood pressure or improve insulin resistance in human subjects with essential hypertension. This trial was registered at clinicaltrials.gov as NCT00099476.

Obtention and characterization of phenolic extracts from different cocoa sources

The aim of this study was to evaluate several cocoa sources to obtain a rich phenol extract for use as an ingredient in the food industry. Two types of phenolic extracts, complete and purified, from different cocoa sources (beans, nibs, liquor, and cocoa powder) were investigated. UPLC-MS/MS was used to identify and quantify the phenolic composition of the extracts, and the Folin-Ciocalteu and vanillin assays were used to determine the total phenolic and flavan-3-ol contents, respectively. The DPPH and ORAC assays were used to measure their antioxidant activity. The results of the analysis of the composition of the extracts revealed that the major fraction was procyanidins, followed by flavones and phenolic acids. From the obtained results, the nib could be considered the most interesting source for obtaining a rich phenolic cocoa extract because of its rich phenolic profile content and high antioxidant activity in comparison with the other cocoa sources.

Analysis of catechins in Theobroma cacao beans by cyclodextrin-modified micellar electrokinetic chromatography

A micellar electrokinetic chromatography (MEKC) method was developed for the quantitation of polyphenols (+)-catechin and (-)-epicatechin (catechin monomers) and the methylxanthine theobromine in Theobroma cacao beans. Owing to the poor stability of catechin monomers in alkaline conditions, a 50 mM Britton-Robinson buffer at a pH 2.50 was preferred as the background electrolyte. Under these conditions, the addition of hydroxypropyl-beta-cyclodextrin (HP-beta-CD) at a concentration of 12 mM to the SDS micellar solution (90 mM), resulted in a cyclodextrin-modified micellar electrokinetic chromatography (CD-MEKC) endowed with two peculiar advantages compare to the conventional MEKC: (i) strong improvement of separation of the most important phytomarkers of T. cacao and (ii) enantioselectivity toward (+/-)-catechin. In particular, separation of methylxanthines (theobromine and caffeine), procyanidin dimers B1 and B2, and catechins (epicatechin and catechin) was obtained simultaneously to the enantioseparation of racemic catechin within 10min. The enantioselectivity of the method makes it suitable in evaluation of possible epimerisation at the C-2 position of epicatechin monomer potentially occurring during heat processing and storage of T. cacao beans. The extraction procedure of the phytomarkers from the beans was approached using ultrasonic bath under mild conditions optimized by a multivariate strategy. The method was validated for robustness, selectivity, sensitivity, linearity, range, accuracy and precision and it was applied to T. cacao beans from different countries; interestingly, the native enantiomer (+)-catechin was found in the beans whereas, for the first time we reported that in chocolate, predominantly (-)-catechin is present, probably yielded by epimerisation of (-)-epicatechin occurred during the manufacture of chocolate.

Vascular protection by dietary polyphenols

Consumption of polyphenol-rich foods, such as fruits and vegetables, and beverages derived from plants, such as cocoa, red wine and tea, may represent a beneficial diet in terms of cardiovascular protection. Indeed, epidemiological studies demonstrate a significant inverse correlation between polyphenol consumption and cardiovascular risk. Among the numerous plausible mechanisms by which polyphenols may confer cardiovascular protection, improvement of the endothelial function and inhibition of angiogenesis and cell migration and proliferation in blood vessels have been the focus of recent studies. These studies have indicated that, in addition to and independently from their antioxidant effects, plant polyphenols (1) enhance the production of vasodilating factors [nitric oxide (NO), endothelium-derived hyperpolarizing factor (EDHF) and prostacyclin] and inhibit the synthesis of vasoconstrictor endothelin-1 in endothelial cells; and (2) inhibit the expression of two major pro-angiogenic factors, vascular endothelial growth factor (VEGF) and matrix metalloproteinase-2 (MMP-2) in smooth muscle cells. The mechanisms of these effects involve: (1) in endothelial cells, increased Ca(2+) level and redox-sensitive activation of the phosphoinositide 3 (PI3)-kinase/Akt pathway (leading to rapid and sustained activation of nitric oxide synthase and formation of EDHF) and enhanced expression of nitric oxide synthase; and (2) in smooth muscle cells, both redox-sensitive inhibition of the p38 mitogen-activated protein kinase (p38 MAPK) pathway activation (leading to inhibition of platelet-derived growth factor (PDGF)-induced VEGF gene expression) and redox-insensitive mechanisms (leading to inhibition of thrombin-induced MMP-2 formation). The current evidence suggests that all these mechanisms are triggered by polyphenols with specific structures, although the structural requirements may be different from one effect to the other, and that they all contribute to the vasoprotective, anti-angiogenic, anti-atherogenic, vasorelaxant and anti-hypertensive effects of acute or chronic administration of plant polyphenols found in vivo in animals and in patients.

Separation of eight selected flavan-3-ols on cellulose thin-layer chromatographic plates

The potential of microcristaline cellulose as sorbent in the separation of eight compounds: (+)-catechin (C), (-)-epicatechin (EC), (-)-gallocatechin (GC), (-)-epigallocatechin (EGC), (-)-epicatechin gallate (ECg), (-)-epigallocatechin gallate (EGCg), procyanidin B1 and procyanidin B2 was studied. Cellulose HPTLC plates prewashed in water (not necessary, when water was used as developing solvent) and dried with a hair dryer, bandwise application and development in horizontal developing chamber (sandwich configuration) gave the best results. Detection was performed using vanillin-H3PO4 reagent. Four new developing solvent systems were proposed: water, 1-propanol-water (20:80, v/v), 1-propanol-water-acetic acid (4:2:1, v/v) and 1-propanol-water-acetic acid (20:80:1, v/v), and at least two of them were needed for the differentiation between all eight compounds. Surprisingly, water enabled the separation of epimers C from EC and GC from EGC, as well as the dimers procianidin B1 and B2. Additionally, C, EGC, B1 and B2 were separated from all the other compounds. The best choice for developing solvent is given for each of the studied compounds. The best separation of the five main catechins (EC, GC, EGC, ECg, EGCg) present in green tea extract was achieved using 1-propanol-water-acetic acid (20:80:1, v/v). The chromatograms of oak bark extract developed in solvents with higher water content (1-propanol-water (1:4, v/v) and 1-propanol-water-acetic acid (20:80:1, v/v)) showed less bands than chromatograms developed in solvents with higher organic modifier content (e.g. 1-propanol-water-acetic acid (4:2:1, v/v)). It was proved that such behavior was due to the presence of procyanidins beside the main component catechin.