Alba Macià

Bioavailability of procyanidin dimers and trimers and matrix food effects in in vitro and in vivo models

Among procyanidins (PC), monomers, such as catechin and epicatechin, have been widely studied, whereas dimer and trimer oligomers have received much less attention, despite their abundance in our diet. Recent studies have showed that as dimers and trimers could be important in determining the biological effects of procyanidin-rich food, understanding their bioavailability and metabolism is fundamental. The purpose of the present work is to study the stability of PC under digestion conditions, the metabolism and the bioavailability by using a combination of in vitro and in vivo models. Simultaneously, the matrix effect of a carbohydrate-rich food on the digestibility and bioavailability of PC is investigated. The results show a high level of stability of PC under gastric and duodenal digestion conditions. However, the pharmacokinetic study revealed limited absorption. Free forms of dimers and trimers have been detected in rat plasma, reaching the maximum concentration 1 h after oral intake of a grape seed extract.

Effect of fat content on the digestibility and bioaccessibility of cocoa polyphenol by an in vitro digestion model.

This work describes the applicability of an in vitro digestion model for the evaluation of the digestibility and bioaccessibility of cocoa polyphenols (procyanidins, phenolic acids, and flavones) and for the study of the food matrix effect in relation with the fat content. For this purpose, two cocoa samples, cocoa liquor ( approximately 50% fat content) and cocoa powder ( approximately 15% fat content), were used. The results showed an important increase of the concentration of procyanidin (monomers and dimers), probably due to the hydrolysis of procyanidins with a high degree of polymerization (pentamers to nonamers) submitted to the digestion procedure. In relation to flavones, the concentration of aglycone forms remained almost constant after the digestion steps; in contrast, the concentration of the glycoside forms an increase in the digestion mixtures mainly after the duodenal step, probably as a result of the partial digestion of the dietary fiber present in the cocoa. The higher fat content in the cocoa liquor seemed to have a protective effect, probably related with a better micellarization that favors the stability of polyphenols during digestion.

Analysis of food polyphenols by ultra high-performance liquid chromatography coupled to mass spectrometry: an overview.

Phenolic compounds, which are widely distributed in plant-derived foods, recently attracted much attention due to their health benefits, so their determination in food samples is a topic of increasing interest. In the last few years, the development of chromatographic columns packed with sub-2μm particles and the modern high resolution mass spectrometry (MS) have opened up new possibilities for improving the analytical methods for complex sample matrices, such as ingredients, foods and biological samples. In addition, they have emerged as an ideal tool for profiling complex samples due to its speed, efficiency, sensitivity and selectivity. The present review addresses the use of the improved liquid chromatography (LC), ultra-high performance LC (UHPLC), coupled to MS or tandem MS (MS/MS) as the detector system for the determination of phenolic compounds in food samples. Additionally, the different strategies to extract, quantify the phenolic compounds and to reduce the matrix effect (%ME) are also reviewed. Finally, a briefly outline future trends of UHPLC-MS methods is commented.

Distribution of olive oil phenolic compounds in rat tissues after administration of a phenolic extract from olive cake

SCOPE The distribution and accumulation of olive oil phenolic compounds in the body are topics lacked of information. The aim of this study was to evaluate the bioavailability, metabolism and distribution of phenolic compounds from olive cake. METHODS AND RESULTS The metabolism and distribution of phenolic compounds were examined by UPLC-MS/MS after an acute intake of a phenolic extract from olive cake, analyzing plasma and tissues (heart, brain, liver, kidney, spleen, testicle and thymus) 1, 2 and 4 h after ingestion using Wistar rats as the in vivo model. The results showed a wide distribution of phenolic compounds and their metabolites in the tissues, with a main detoxification route through the kidneys. Highlighting the quantification of the free forms of some phenolic compounds, such as oleuropein derivative in plasma (Cmax 4 h: 24 nmol/L) and brain (Cmax 2 h: 2.8 nmol/g), luteolin in kidney (Cmax 1 h: 0.04 nmol/g), testicle (Cmax 2 h: 0.07 nmol/g) and heart (Cmax 1 h: 0.47 nmol/g); and hydroxytyrosol in plasma (Cmax 2 h: 5.2 nmol/L), kidney (Cmax 4 h: 3.8 nmol/g) and testicle (Cmax 2 h: 2.7 nmol/g). CONCLUSION After a single ingestion of olive oil phenolic compounds, these were absorbed, metabolized and distributed through the blood stream to practically all parts of the body, even across the blood-brain barrier.

Determination of procyanidins and their metabolites in plasma samples by improved liquid chromatography–tandem mass spectrometry

An off-line solid-phase extraction (SPE) and ultra-performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS) method was developed and validated for determining procyanidins, catechin, epicatechin, dimer, and trimer in plasma samples. In the validation procedure of the analytical method, linearity, precision, accuracy, detection limits (LODs), quantification limits (LOQs), and the matrix effect were studied. Recoveries of the procyanidins were higher than 84%, except for the trimer, which was 65%. The LODs and LOQs were lower than 0.003 and 0.01 microM, respectively, for all the procyanidins studied, except for the trimers, which were 0.8 and 0.98 microM, respectively. This methodology was then applied for the analysis of rat plasma obtained 2h after ingestion of grape seed phenolic extract. Monomers (catechin and epicatechin), dimer and trimer in their native form were detected and quantified in plasma samples, and their concentration ranged from 0.85 to 8.55 microM. Moreover, several metabolites, such as catechin and epicatechin glucuronide, catechin and epicatechin methyl glucuronide, and catechin and epicatechin methyl-sulphate were identified. These conjugated forms were quantified, in reference to the respective unconjugated form, showing concentrations between 0.06 and 23.90 microM.

Methods for Preparing Phenolic Extracts from Olive Cake for Potential Application as Food Antioxidants

Olive cake, the most important byproduct of olive oil extraction by the two-phase centrifugation system, was used to obtain phenolic extracts. The extracts were obtained using the two constituents of this waste, vegetative water and solid residue, to maximize the extraction of all phenolic compounds. Different extraction procedures were studied, a simple and rapid extraction procedure being developed from the solid residue using an accelerated solvent extractor (ASE). Afterward, the phenolic extracts were fractionated using semipreparative HPLC to study the antioxidant activity of the different components. The identification of the phenolic compounds was carried out with an ultraperformance liquid chromatograph coupled to tandem mass spectrometry equipment (UPLC-ESI-MS/MS). With this method, a complete list of the polyphenols from the extract was obtained. Finally, the antioxidant activity of the phenolic extracts and the isolated fractions was evaluated, showing great antioxidant capacities, between 3450 and 17900 micromol of Trolox equivalents/g of extract. With regard to the isolated fractions the most antioxidant were those that contained hydroxytyrosol and 3,4-DHPEA-EDA. The suitability of the solid residue extract obtained by the ASE procedure was demonstrated given the great range of phenolic compounds and the feasibility of production on an industrial scale.

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.

Bioavailability of phenols from a phenol-enriched olive oil

Phenolic compounds are one of the main reasons behind the healthy properties of virgin olive oil (VOO). However, their daily intake from VOO is low compared with that obtained from other phenolic sources. Therefore, the intake of VOO enriched with its own phenolic compounds could be of interest to increase the daily dose of these beneficial compounds. To evaluate the effectiveness of enrichment on their bioavailability, the concentration of phenolic compounds and their metabolites in human plasma (0, 60, 120, 240 and 300 min) from thirteen healthy volunteers (seven men and six women, aged 25 and 69 years) was determined after the ingestion of a single dose (30 ml) of either enriched virgin olive oil (EVOO) (961·17 mg/kg oil) or control VOO (288·89 mg/kg oil) in a cross-over study. Compared with VOO, EVOO increased plasma concentration of the phenol metabolites, particularly hydroxytyrosol sulphate and vanillin sulphate (P < 0·05). After the consumption of VOO, the maximum concentration of these peaks was reached at 60 min, while EVOO shifted this maximum to 120 min. Despite these differences, the wide variability of results indicates that the absorption and metabolism of olive oil phenols are highly dependent on the individual.

Rapid analysis of procyanidins and anthocyanins in plasma by microelution SPE and ultra‐HPLC

In the analysis of biological samples, such as plasma or serum, the quantity of sample available is a critical parameter in most cases. A good approach is the use of the microelution SPE (μSPE) plates as sample pre-treatment technique in which the loaded sample volume is low. An off-line μSPE and ultra-performance LC-ESI-MS/MS (UPLC-ESI-MS/MS) method was developed and validated to determine procyanidins and anthocyanins in spiked plasma samples. The sample pre-treatment μSPE allowed the simultaneous determination of procyanidins and anthocyanins from plasma by using a small sample volume (350 μL) and without an evaporation step previous to the chromatographic analysis. Moreover, the use of UPLC technique allowed to determine the studied compounds at low concentration levels in a short analysis time (12.5 min approximately). Then, the developed method was applied to determine the studied compounds, procyanidins and anthocyanins, and their metabolites in rat plasma samples. Previously, the rats had consumed 5000 mg/kg of a grape pomace extract and the plasma was extracted 4 h after administration. The procyanidins catechin and epicatechin glucuronide, methyl catechin and epicatechin glucuronide, and methyl catechin and epicatechin sulphate were detected at μM concentration level, and the parent anthocyanins at nM.

Impact of olive oil phenolic concentration on human plasmatic phenolic metabolites

Three different functional phenol-enriched virgin olive oils (FVOO) were prepared with a phenolic content of 250 (L-FVOO), 500 (M-FVOO), and 750 mg (H-FVOO) total phenols/kg. In a randomised, cross-over study with 12 healthy volunteers, the pharmacokinetics of phenolic biological metabolites was assessed. An increasing linear trend was observed for hydroxytyrosol sulfate, the main phenolic metabolite quantified in plasma, with C(max) values of 1.35, 3.32, and 4.09 μmol/l, and AUC mean values of 263.7, 581.4, and 724.4 μmol/min for L-FVOO, M-FVOO, and H-FVOO, respectively. From our data an acute intake of phenol-enriched olive oils promotes a dose-dependent response of phenol conjugate metabolites in human plasma. Also, we point out for the first time hydroxytyrosol acetate sulfate as a main biological metabolite of hydroxytyrosol from olive oil ingestion.