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Flavan-3-ols intake is associated with numerous health benefits, but these are influenced by their conversion into smaller phenolic metabolites by the gut microbiota. Thus, the identification of bacteria that metabolize flavan-3-ols could lead to targeted interventions to enhance their benefits. To this end, we screened 47 Lactiplantibacillus plantarum strains for their ability to metabolize (+)-catechin, a flavan-3-ol. Then, we assessed these strains for their capacity to convert various flavan-3-ol structures. Out of the 47 isolates, 12 released 3-(3',4'-dihydroxyphenyl)-1-(2,4,6-trihydroxyphenyl)-propan-2-ol (a form of diphenylpropan-2-ol) from (+)-catechin. All strains metabolized (+)-catechin, (-)-epicatechin, (-)-epigallocatechin, but only a subset transformed (-)-gallocatechin. Among these simple flavan-3-ol structures, (-)-epicatechin was metabolized the most. A hierarchical cluster analysis identified two groups of flavan-3-ol-metabolizing strains categorized as having "high" and "low" production of diphenylpropan-2-ols. Notably, the strains that produced higher levels of diphenylpropan-2-ol from (+)-gallocatechin and (+)-catechin also performed better with a camu-camu extract, which was studied as a complex source of flavan-3-ols and predominantly contained these two flavan-3-ols. These results demonstrate the interstrain variability in L. plantarum metabolism, which may be useful for developing tailored formulations to enhance the production of flavan-3-ols bioactive metabolites.

Quantification of nutritional biomarkers is crucial to accurately assess the dietary intake of different classes of (poly)phenols in large epidemiological studies. High-throughput analysis is mandatory to apply this methodology in large cohorts. However, the current validated methods to quantify (poly)phenols metabolites in biological fluids use ultra performance liquid chromatography (UPLC), leading to analysis time of several minutes per sample. To significantly reduce the run time, we developed and validated a method to quantify in urine the flavan-3-ols biomarkers, phenyl-γ-valerolactones (PVLs), using laser diode thermal desorption (LDTD). This mass spectrometry source allows direct introduction of sample extracts, resulting in analysis time of less than 10 s per sample. Also, to encompass the problem associated with the cost and availability of sulfated and glucuronide analytical standards, urine samples were subjected to enzymatic hydrolysis. Creatinine was also quantified to normalize the results obtained from the urinary spot. Results obtained with LDTD-MS/MS were cross-validated by UPLC-MS/MS using 155 urine samples. Coefficient of correlation was above 0.975 for PVLs and creatinine. For all analytes, the accuracy was between 90% and 113% by LDTD-MS/MS. Altogether, sample preparation was fully automated to demonstrate the application potential of this method to large cohorts.

We investigated changes in the phenolic profile and antioxidant properties in the extracts of developing seeds of açaí ( Euterpe oleracea ). Four developmental stages were evaluated, with earlier stages displaying higher antioxidant activity and polyphenols content, while mass spectrometry analysis identified procyanidins (PCs) as the major components of the extracts in all stages. B-type PCs varied from dimers to decamers, with A-type linkages in a smaller number. Extracted PCs decreased in average length from 20.5 to 10.1 along seed development. PC composition indicated that (-)-epicatechin corresponded to over 95% of extension units in all stages, while (+)-catechin presence as the starter unit increased from 42 to 78.8% during seed development. This variation was correlated to the abundance of key enzymes for PC biosynthesis during seed development. This study is the first to report PC content and composition variations during açaí seed development, which can contribute to studies on the plant's physiology and biotechnological applications.

Astringency is a highly complex sensation which involves multiple mechanisms occurring simultaneously, such as the interaction between flavan-3-ols and salivary proteins (SP). Moreover, astringency development can be affected by the presence of polysaccharides such as mannoproteins (MP). The aim of this work was to evaluate the molecular mechanisms whereby MP could modulate the astringency elicited by tannins, using a cell-based model of the oral epithelium (TR146 cells), and the effect of salivary proteins on these interactions. The binding of flavan-3-ols to oral cells was evaluated by DMACA assay, while the content of unbound flavan-3-ols after the interactions was assessed by means of HPLC-DAD-MS. Results obtained confirm the existence of cell-tannin interactions, that can be partially inhibited by the presence of SP and/or MP. The most significant decrease was obtained in the system containing MPF (38.16%). Both mannoproteins assayed seem to have modulating effect on flavan-3-ol-SP interactions, acting by two different mechanisms: MPF would lead to the formation of SP/MPF/flavan-3-ols ternary soluble aggregates, while MPL seems to prevent flavan-3-ol-saliva interaction by a competitive mechanism, i.e., MPL would reduce cell-tannin interactions, similar to SP. This study suggests that mannoproteins with different compositional characteristics could exhibit preferential interaction with distinct flavan-3-ol families.

Flavan-3-ols are a group of flavonoids that exert beneficial effects. This study aimed to enhance key metabolic processes related to flavan-3-ols biosynthesis. The engineered Saccharomyces cerevisiae strain E32 that produces naringenin from glucose was further engineered for de novo production of two basic flavan-3-ols, afzelechin (AFZ) and catechin (CAT). Through introduction of flavonoid 3-hydroxylase, flavonoid 3'-hydroxylase, dihydroflavonol 4-reductase (DFR), and leucoanthocyanidin reductase (LAR), de novo production of AFZ and CAT can be achieved. The combination of Fa DFR from Fragaria × ananassa and Vv LAR from Vitis vinifera was optimal. (GGGGS) 2 and (EAAAK) 2 linkers between DFR and LAR proved optimal for the production of AFZ and CAT, respectively. Optimization of promoters and the enhanced supply of NADPH further increased the production. By combining the best engineering strategies, the optimum strains produced 500.5 mg/L AFZ and 321.3 mg/L CAT, respectively, after fermentation for 90 h in a 5 L bioreactor. The strategies presented could be applied for a more efficient production of flavan-3-ols by various microorganisms.

Plant defense inducers (PDIs) are booming and attractive protection agents designed to immunostimulate the plant to reduce subsequent pathogen colonization. The structure-PDI activity relationships of four flavan-3-ols: Epicatechin (EC), Epigallocatechin (EGC), Epicatechin gallate (ECG), Epigallocatechin gallate (EGCG) and Gallotannic acid (GTA) were investigated in both whole plant and suspension cell systems. ECG, EGCG, and GTA displayed elicitor activities. Their infiltration into tobacco leaves induced hypersensitive reaction-like lesions with topical scopoletin and PR-target transcript accumulations. On the contrary, EC and EGC infiltrations fail to trigger the biochemical changes in tobacco tissues. The tobacco BY-2 cells challenged with ECG, EGCG, or GTA led to alkalinization of the BY-2 extracellular medium while EC and EGC did not trigger any pH variation. This work provides evidence that the esterified gallate pattern is as an essential flavonoid entity to induce plant defense reactions in tobacco. The phytoprotective properties of the esterified gallate-free EC and the esterified gallate-rich GTA were evaluated on the tobacco/ Phytophthora parasitica var. nicotianae ( Ppn ) pathosystem. Tobacco treatment with EC did not induce significant protection against Ppn compared to GTA which shows antimicrobial properties on Ppn and decreases the infection on GTA-infiltrated and -sprayed wild-type leaves. GTA protection was impaired in the transgenic NahG tobacco plants, suggesting that protection was mediated by salicylic acid.

The oxidative behavior of five commercial enological tannins of different sources (tea, grape marc, grape seed, untoasted oak, and toasted oak) was investigated in model wine solutions in the presence or absence of SO 2 . Solutions of the tannins were also analyzed for total phenolics, methyl cellulose precipitable tannins, high-performance liquid chromatography, and linear sweep voltammetry. Tea and oak-derived tannin solutions were characterized by the highest oxygen consumption rates, with oak-derived tannins exhibiting the highest oxygen consumption rates per milligram of phenolic material present. Linear sweep and derivative voltammetry parameters were well-correlated with oxygen consumption rates, whereas total phenolics or total tannins were not. All tannins were associated with consumption of SO 2 upon reaction with oxygen, with the lowest rate of SO 2 lost per milligram of O 2 reacted being observed for oak tannins.

Berries of genus Vaccinium are rich in flavonoids and proanthocyanidins (PAs). We studied the PA composition and biosynthesis in bilberry ( Vaccinium myrtillus L.) tissues and during fruit development. Soluble PAs, analyzed by UHPLC-MS/MS, were most abundant in stem and rhizome with the mean PA polymerization level varying between 4 and 6 in all tissues. Both A- and B-type PAs were present in all tissues. Procyanidin subunits were more common than prodelphinidin subunits in PAs. During fruit ripening, the amount of procyanidin subunits decreased while prodelphinidin subunits and F3'5'H expression increased, indicating a shift in biosynthesis toward the delphinidin branch of the flavonoid pathway. Epicatechin was the most abundant flavan-3-ol in all tissues. Expression of ANR and three isolated LAR genes, analyzed by qRT-PCR, showed connection to accumulation of PAs and flavan-3-ols biosynthesized from different flavonoid branches. Insoluble PAs accumulated during berry development, suggesting that PAs are not recycled after biosynthesis.

As a result of the high variability of fruit properties in the European plum Prunus domestica , a histochemical analysis of fruits at different stages of development was performed to understand the ripening process in cv. 'Colora' (yellow-red skinned) and cv. 'Topfive' (purple skinned). Histological analysis showed that carotenoids in the fruit had two different origins. In the fruit flesh, they derived from chloroplasts that turned into chromoplasts, whereas carotenoids in the fruit skin derived probably from proplastids. Flavan-3-ols and proanthocyanidins showed differential localization during ripening. They were visible in the vacuole in different fruit tissues or organized in tannosomes in the fruit flesh. Tanninoplasts were observed only in hypodermal cells of 'Colora'. Toward maturity, anthocyanins were detected in the epidermis and later in the hypodermis of both cultivars. The study forms a basis for the analysis of the biosynthesis of secondary metabolites in European plums and their biological effects.

Tea, as one of the most popular beverages with various bioactivities, is commonly produced from the fresh leaves of two widely cultivated tea plants, Camellia sinensis and C. sinensis var. assamica. Both plants belong to the genus Camellia section Thea, which was considered to have 12 species and 6 varieties according to Min's taxonomic system. Most species, except the cultivated species, are known as wild tea plants and have been exploited and utilized to produce tea by the local people of its growing areas. Thus far, six species and varieties have been phytochemically studied, leading to the identification of 398 compounds, including hydrolyzable tannins, flavan-3-ols, flavonoids, terpenoids, alkaloids, and other phenolic and related compounds. Various beneficial health effects were reported for tea and its components, involving antioxidant, antitumor, antimutagenic, antidiabetic, hypolipidemic, anti-inflammatory, antimicrobial, antiviral, antifungal, neuroprotective, hepatoprotective, etc. In this review, the geographical distribution of tea plants and the chemical constituents (1-398) reported from the genus Camellia section Thea and some tea products (green, black, oolong, and pu-erh tea) that have ever been studied between 1970 and 2018 have been summarized, taking species as the main hint, and the main biological activities are also discussed.

This work aims to sort cocoa beans according to chocolate sensory quality and phenolic composition. Prior to the study, cocoa samples were processed into chocolate in a standard manner, and then the chocolate was characterized by sensory analysis, allowing sorting of the samples into four sensory groups. Two objectives were set: first to use average mass spectra as quick cocoa-polyphenol-extract fingerprints and second to use those fingerprints and chemometrics to select the molecules that discriminate chocolate sensory groups. Sixteen cocoa polyphenol extracts were analyzed by liquid chromatography-low-resolution mass spectrometry. Averaging each mass spectrum provided polyphenolic fingerprints, which were combined into a matrix and processed with chemometrics to select the most meaningful molecules for discrimination of the chocolate sensory groups. Forty-four additional cocoa samples were used to validate the previous results. The fingerprinting method proved to be quick and efficient, and the chemometrics highlighted 29 m/ z signals of known and unknown molecules, mainly flavan-3-ols, enabling sensory-group discrimination.

Despite the economic importance and the diffusion of grapevine cultivation worldwide, little is known about leaf chemical composition. We characterized the phenolic composition of Nebbiolo, Barbera, Pinot noir, Cabernet Sauvignon, Grenache, and Shiraz ( Vitis vinifera L.) healthy leaves (separating blades and veins) during the season. Quantitative and qualitative differences were found between leaf sectors and among genotypes. In healthy grapevine leaves, anthocyanins, dihydromyricetin-rhamnoside, hexosides of dihydroquercetin, and dihydrokaempferol exclusively accumulated in veins. Astilbin was the only flavanonol detected in blades and the prevalent flavanonol in veins. Barbera distinguished for the lowest proanthocyanidin and the highest hydroxycinnamate content, and Pinot noir for the absence of acylated-anthocyanins. Nebbiolo, and Cabernet Sauvignon displayed a high concentration of epigallocatechin gallate in veins. Nebbiolo leaves showed the highest concentrations of flavanonols and the widest profile differentiation. Knowledge derived from the present work is a contribution to find out leaf polyphenol potential as a part of grapevine defense mechanisms and to dissect genotype-related susceptibility to pathogens; moreover, it represents a starting point for future deepening about grapevine and vineyard byproducts as a source of bioactive phenolic compounds.

Proanthocyanidins (PAs) are widespread oligomeric and polymeric flavan-3-ols with significant benefits to human and animal health. As products of the general flavonoid pathway, the biosynthesis of the flavan-3-ols is well-understood and the major enzyme-encoding genes that determine PA structure have been identified. However, the mechanism of PA polymerization remains unknown. The most important transcription factors regulating PA biosynthesis are the MYB factors, potent tools for enhancing PA biosynthesis in plants. In some species, simple overexpression of these transcription factors has led to spectacular successes in upregulating PA synthesis. However, targeted metabolic engineering of the PA structure has not yet been achieved.

The variable anthelmintic efficacy of condensed tannins (CT) against gastrointestinal nematodes may depend on CT concentration, composition, or fate along the digestive tract. We analyzed CT concentration and composition by acetone-HCl-butanol and thiolysis coupled to HPLC-MS in digesta and feces of lambs. Lambs had been infected with Haemonchus contortus and Trichostrongylus colubriformis and received sainfoin pellets and hazelnut skins of contrasting prodelphinidin/procyanidin ratios. The digesta and feces had lower CT concentrations than the original feeds but similar concentration patterns across the digestive compartments. The changes in assayable CT concentrations between rumen, abomasum, and small intestine may be due to complex formation between CT and other dietary components. However, the large CT disappearance (61-85%) from feed to feces could also indicate that CT may have been structurally modified, degraded, or absorbed during digestion. Interestingly, there were no changes in the structural features of assayable CT in the digesta.

Grape seed proanthocyanidins, composed of flavan-3-ols of different degrees of polymerization, are natural food antioxidants. Flavan-3-ols in grape seed are usually polyhydroxy derivatives which exhibit hydrophilic character. Monomeric and oligomeric flavan-3-ols were modified structurally to improve their lipophilicity, expand their application in lipophilic media, and enhance their cellular absorption in the body. The esterification of the water-soluble flavan-3-ols was prepared by Lipozyme TL IM with lauric acid, and their enhanced lipophilicity was confirmed by a 1-octanol/water partition coefficient. The chemical structures of monomeric and oligomeric flavan-3-ol derivatives, identified by HPLC-MS-MS and 1 H and 13 C NMR, were 3'-O-lauroyl catechin, 3'-O-lauroyl epicatechin, 3',5'-2-O-lauroyl epigallocatechin, 3',3″,5″-3-O-lauroyl epicatechin gallate, 3',3″-2-O-lauroyl procyanidin A2, 3',3″-2-O-lauroyl procyanidin B1, and 3',3″,3‴-3-O-lauroyl procyanidin C1. Flavan-3-ol derivatives exhibited the highest 1,1-diphenyl-2-picrylhydrazyl and 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) radical scavenging activities compared to that of parent flavan-3-ols, butylated hydroxytoluene and tert-butyl hydroquinone. The results suggest that flavan-3-ol derivatives may be used as potential lipophilic antioxidants in the food industry.

The interactions between salivary proteins and wine flavanols (catechin, epicatechin, and mixtures thereof) have been studied by HPLC-DAD, isothermal titration microcalorimetry, and molecular dynamics simulations. Chromatographic results suggest that the presence of these flavanol mixtures could facilitate the formation of precipitates to the detriment of soluble aggregates. Comparison between the thermodynamic parameters obtained showed remarkably higher negative values of ΔG in the system containing the mixture of both flavanols in comparison to the systems containing individual flavanols, indicating a more favorable scenario in the mixing system. Also, the apparent binding constants were higher in this system. Furthermore, molecular dynamics simulations suggested a faster and greater cooperative binding of catechin and epicatechin to IB7 14 peptides when both types of flavanols are present simultaneously in solution.

Cranberry is reported to have health benefits, including prevention of urinary tract infections and other chronic diseases, due to the high content of polyphenols, including flavonols and flavan-3-ols. The aim of this study was to determine the clearance of flavonol glycosides and flavan-3-ols and/or their metabolites in human urine. Ten healthy women volunteers ingested 240 mL of cranberry juice containing flavonol glycosides. Urine samples were collected at 0, 90, 225, and 360 min postingestion. While flavan-3-ols were not detected, five flavonol glycosides common in cranberry were identified. Quercetin-3-galactoside, the most abundant cranberry flavonol, exhibited the highest peak urine concentration (C max ) of 1315 pg/mg creatinine, followed by quercetin-3-rhamnoside, quercetin-3-arabinoside, myricetin-3-arabinoside, and myricetin-3-galactoside. Quercetin-3-arabinoside showed delayed clearance, C max at 237 min (T max ), relative to other flavonols (90-151 min). Both aglycone and the conjugated sugar moiety structure mediate the flavonol's bioavailability. Interindividual variation for bioavailability and clearance is also apparent. Metabolites, e.g. glucoronides, were not detected.

Polyphenol profiles and in vitro digestive enzyme inhibitory activities were compared between cocoa extracts from unfermented beans (UB), fermented beans (FB), unfermented liquor (UL), and fermented liquor (FL). Total polyphenols, total flavanols, and individual flavanols were significantly different between UB/FB and UL/FL. All extracts effectively inhibited α-glucosidase (lowest IC50 = 90.0 μg/mL, UL) and moderately inhibited α-amylase (lowest IC50 = 183 μg/mL, FL) and lipase (lowest IC25 = 65.5 μg/mL, FB). Our data suggest that fermentation does not reduce α-glucosidase inhibition, while roasting may enhance inhibition. For α-amylase, both fermentation and roasting improved inhibition. Finally, for lipase, both fermentation and roasting attenuated inhibition. Conclusive correlations between inhibition and mDP, total polyphenol, and flavanol contents were not found. Our data suggest that enzyme inhibition activities of cocoa are not uniformly reduced by polyphenol/flavanol losses during fermentation and roasting. This paradigm-challenging finding suggests other cocoa constituents, potentially formed during processing, contribute to digestive enzyme inhibition.

Proanthocyanidins are a class of polyphenols present in many foodstuffs (i.e., tea, cocoa, berries, etc.) that may reduce the risk of several chronic diseases. Barley, with sorghum, rice, and wheat, are the only cereals that contain these compounds. Because of that, two barley genotypes, named waxy and non-waxy, were analyzed by normal-phase high-performance liquid chromatography-fluorescence detection-mass spectrometry (NP-HPLC-FLD-MS). Total proanthocyanidin content ranged between 293.2 and 652.6 μg/g of flour. Waxy samples reported the highest content (p < 0.05) of proanthocyanidins. Dimer compounds were the principal proanthocyanidin constituents of barley samples. Moreover, the possibility to use near-infrared (NIR) spectroscopy as a rapid method to discriminate between waxy and non-waxy samples and to predict quantitatively proanthocyanidins in barley samples was evaluated. Partial least squares (PLS) models were built to predict the proanthocyanidin constituent, obtaining determination coefficients (R(2)) ranging from 0.92 to 0.97, in test set validation. Because of that, this study highlights that NIR spectroscopy technology with multivariate calibration analysis could be successfully applied as a rapid method to determine proanthocyanidin content in barley.