flavan-3-ol and gallocatechol

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/

Topics: Catechin; Flavonoids; Molecular Structure; Nicotiana; Phytophthora; Plant Diseases; Plant Leaves

One of the best-studied defense responses to fungal infection in Norway spruce (Picea abies) is the biosynthesis of flavan-3-ols, which accumulate as monomers or polymers known as proanthocyanidins. The individual flavan-3-ol units consist of compounds with a 3',4'-dihydroxylated B ring [2,3-(trans)-(+)-catechin or 2,3-(cis)-(-)-epicatechin] and compounds with a 3',4',5'-trihydroxylated B ring [2,3 (trans)-(+)-gallocatechin or 2,3-(cis)-(-)-epigallocatechin]. While much is known about the biosynthesis and biological activity of catechin in Norway spruce, there is little comparable information about gallocatechin or epigallocatechin. We found that there was a significant increase in the gallocatechin content of Norway spruce bark and wood after inoculation with the bark beetle-associated sap-staining fungus Endoconidiophora polonica. Gallocatechins increased proportionally more than catechins as both monomers and units of polymers. A flavonoid 3',5'-hydroxylase gene identified in Norway spruce was shown by heterologous expression in Nicotiana benthamiana to be involved in the conversion of 2,3 (trans)-(+)-catechin to 2,3 (trans)-(+)-gallocatechin. The formation of the trihydroxylated B ring in Norway spruce occurs at the level of flavan-3-ols, rather than at the level of dihydroflavonols as in many angiosperms. The transcript abundance of the flavonoid 3',5'-hydroxylase gene also increased significantly during fungal infection underlining its importance in gallocatechin biosynthesis. Comparisons of the effect of 2,3 (trans)-(+)-catechin and 2,3 (trans)-(+)-gallocatechin on fungal growth revealed that 2,3 (trans)-(+)-catechin is a stronger inhibitor of fungal growth, while 2,3 (trans)-(+)-gallocatechin is a stronger inhibitor of melanin biosynthesis.

Topics: Animals; Ascomycota; Catechin; Coleoptera; Cyclopentanes; Cytochrome P-450 Enzyme System; Flavonoids; Mixed Function Oxygenases; Norway; Oxylipins; Picea; Plant Bark; Plant Diseases; Terpenes

The identification of cyclic B-type procyanidins in grape and wine was recently disclosed. Some of these were also found in berries of totally different vegetal species (eg, Vaccinium sp.). However, presence of a wider class of these cyclic condensed tannin compounds with variably substituted monomers has never been addressed so far. Here, an extended list of oligomeric cyclic proanthocyanidins (PAC) bearing variable substitution patterns on the main flavan-3-ol unit has been searched in wines. Nearly 7600 theoretical structures were calculated and searched in red and white wine samples made from different grape varieties. Moreover, a hydrogen/deuterium exchange approach (already applied to a cyclic tetrameric procyanidin) coupled to high-resolution mass spectrometry was applied to confirm their cyclic B-type structure rather than a non cyclic A-type structure, otherwise isomeric and undistinguishable by LC-MS alone. The main group of novel cyclic PAC observed is shown to contain (epi)gallocatechin beside (epi)catechin as the constituent monomers.

Topics: Catechin; Chromatography, High Pressure Liquid; Deuterium; Flavonoids; Isotope Labeling; Molecular Structure; Proanthocyanidins; Tandem Mass Spectrometry; Vitis; Wine

Interactions between polyphenols and macromolecules may impact polyphenol stability and bioavailability from foods. The impact of milk on tea flavan-3-ol stability to thermal treatment was investigated. Single strength (36.2 protein per L), quarter strength (9.0 g protein per L) milk, and control model beverages were incubated with epigallocatechin gallate and green tea extract at 62 or 37 °C for 180 min. Intact flavan-3-ols and select auto-oxidation products [theasinesins (THSNs) and P-2 dimers] were quantified by LC-MS. Generally, greater polyphenol to protein ratios increased first order degradation rates, consequently decreasing formation of oxidation products. The presence of galloyl and hydroxy moieties was associated with higher stability of monomeric flavan-3-ols with increasing protein concentrations suggesting potential for protein affinity to stabilise flavan-3-ols to thermal treatment. Absence of these moieties led to no observable improvements in stability. These results suggest that protein interactions may be useful in stabilising flavan-3-ols through thermal processing.

Topics: Animals; Beverages; Catechin; Dietary Proteins; Flavonoids; Food Handling; Milk; Polyphenols; Tea

The present study was designed to investigate the bioactive constituents of Xanthoceras sorbifolia in terms of amounts and their antioxidant, DNA scission protection, and α-glucosidase inhibitory activities. Simultaneous quantification of 10 X. sorbifolia constituents was carried out by a newly established ultra-high performance liquid chromatography-quadrupole mass spectrometry method (UHPLC-MS). The antioxidant activities were evaluated by measuring DPPH radical scavenging and DNA scission protective activities. The α-glucosidase inhibitory activities were investigated by using an assay with α-glucosidase from Bacillus Stearothermophilus and disaccharidases from mouse intestine. We found that the wood of X. sorbifolia was rich in phenolic compounds with the contents of catechin, epicatechin, myricetin, and dihydromyricetin being 0.12-0.19, 1.94-2.16, 0.77-0.91, and 6.76-7.89 mg·g(-1), respectively. The four constituents strongly scavenged DPPH radicals (with EC50 being 4.2, 3.8 and 5.7 μg·mL(-1), respectively) and remarkably protected peroxyl radical-induced DNA strand scission (92.10%, 94.66%, 75.44% and 89.95% of protection, respectively, at a concentration of 10 μmol·L(-1)). A dimeric flavan 3-ol, epigallocatechin-(4β→8, 2β→O-7)-epicatechin potently inhibited α-glucosidase with an IC50 value being as low as 1.2 μg·mL(-1). The established UHPLC-MS method could serve as a quality control tool for X. sorbifolia. In conclusion, the high contents of antioxidant and α-glucosidase inhibitory constituents in X. sorbifolia support its use as complementation of other therapeutic agents for metabolic disorders, such as diabetes and hypertension.

Topics: alpha-Glucosidases; Antioxidants; Biphenyl Compounds; Catechin; Chromatography, High Pressure Liquid; DNA; DNA Damage; Flavonoids; Glycoside Hydrolase Inhibitors; Mass Spectrometry; Picrates; Plant Extracts; Sapindaceae; Triterpenes; Wood

Brown cotton fiber is the major raw material for colored cotton industry. Previous studies have showed that the brown pigments in cotton fiber belong to proanthocyanidins (PAs). To clarify the details of PA biosynthesis pathway in brown cotton fiber, gene expression profiles in developing brown and white fibers were compared via digital gene expression profiling and qRT-PCR. Compared to white cotton fiber, all steps from phenylalanine to PA monomers (flavan-3-ols) were significantly up-regulated in brown fiber. Liquid chromatography mass spectrometry analyses showed that most of free flavan-3-ols in brown fiber were in 2, 3-trans form (gallocatechin and catechin), and the main units of polymeric PAs were trihydroxylated on B ring. Consistent with monomeric composition, the transcript levels of flavonoid 3', 5'-hydroxylase and leucoanthocyanidin reductase in cotton fiber were much higher than their competing enzymes acting on the same substrates (dihydroflavonol 4-reductase and anthocyanidin synthase, respectively). Taken together, our data revealed a detailed PA biosynthesis pathway wholly activated in brown cotton fiber, and demonstrated that flavonoid 3', 5'-hydroxylase and leucoanthocyanidin reductase represented the primary flow of PA biosynthesis in cotton fiber.

Topics: Biosynthetic Pathways; Catechin; Cotton Fiber; Flavonoids; Gene Expression Profiling; Gene Expression Regulation, Plant; Gossypium; Oxidoreductases; Plant Leaves; Plant Proteins; Proanthocyanidins; Transcriptome; Up-Regulation

The accumulation of flavan-3-ols in response to ultraviolet (UV) irradiation was investigated in grape berries with emphasis on the expression of three structural genes (VvANR, VvLAR1 and VvLAR2), and three regulatory genes (VvMYB5a, VvMYB5b and VvMYBPA1), and as well as the contents of flavan-3-ols. UV-A irradiation showed a promoting effect on the transcription of three structural genes at 3-week (flavan-3-ol accumulation period), 7-week (the end of flavan-3-ol accumulation) and 11-week (the beginning of anthocyanin synthesis) periods of berry development. UV-B irradiation also up-regulated all or part of the structural genes, but the activation effect of UV-C irradiation appeared only in the 7-week and 11-week grapes. The developmental stage-dependent activation by the three types of UV was also initiated for three regulatory genes, but the transcriptional up-regulation of the structural genes by UV irradiation was not entirely regulated by these transcription factors. The increase in the content of 2,3-trans-flavan-3-ols or 2,3-cis-flavan-3-ols by UV irradiation paralleled overall with the expression up-regulation of their corresponding structural genes in the 3-week and the 7-week grapes, but not in the 11-week grapes, indicating that the overexpression of structural genes by UV radiation does not translate into a higher content of flavan 3-ols at mature stage.

Topics: Analysis of Variance; Anthocyanins; Biosynthetic Pathways; Catechin; Flavonoids; Fruit; Gene Expression Regulation, Developmental; Gene Expression Regulation, Plant; Genes, Plant; Plant Proteins; Real-Time Polymerase Chain Reaction; Time Factors; Transcriptional Activation; Ultraviolet Rays; Vitis

Because consumption of teas may be associated with potential health benefits due to its content in polyphenols and in Western countries the consumption of tea is equally divided between the hot and the ready-to-drink (RTD) cold versions of this typical beverage, the aim of this work was to study the absorption and metabolism of flavan-3-ols in human volunteers after the ingestion of a commercial RTD tea.. A feeding study was carried out in 20 healthy human volunteers and urine samples were collected for 24h after tea ingestion. Flavan-3-ols-derived molecules were identified and quantified in urine samples by high-performance liquid chromatography with tandem mass spectrometric detection.. Eight relevant metabolites were identified in urine, all modified flavan-3-ols with the exception of unmetabolized gallic acid. The urinary excretion of flavan-3-ols was equal to 7.2% of the intake with tea. Gallic acid, which was abundant in the RTD tea used in this study, reached a 4.5% of the drunken amount.. The bioavailability values observed are in agreement with previous reports, although the dosage of polyphenols ingested in this study is remarkably lower. Moreover, the use of a group of 20 volunteers, more than the average number of subjects used for usual human acute-feeding studies involving polyphenols, provides additional credibility to the results. After drinking the RTD ice tea used in this study, the internal compartments are exposed to non-marginal doses of flavanols and flavanol metabolites up to 24h.

Topics: Adolescent; Adult; Biological Availability; Catechin; Chromatography, High Pressure Liquid; Female; Flavonoids; Gallic Acid; Humans; Male; Middle Aged; Tandem Mass Spectrometry; Tea

Ten healthy human subjects consumed 500 mL of Choladi green tea, containing 648 mumol of flavan-3-ols after which plasma and urine were collected over a 24 h period and analysed by HPLC-MS. Plasma contained a total of ten metabolites, in the form of O-methylated, sulphated and glucuronide conjugates of (epi)catechin and (epi)gallocatechin, with 29-126 nM peak plasma concentrations (C(max)) occurring 1.6-2.3 h after ingestion, indicative of absorption in the small intestine. Plasma also contained unmetabolised (-)-epigallocatechin-3-gallate and (-)-epicatechin-3-gallate with respective C(max) values of 55 and 25 nM. Urine excreted 0-24 h after consumption of green tea contained 15 metabolites of (epi)catechin and (epi)gallocatechin, but (-)-epigallocatechin-3-gallate and (-)-epicatechin-3-gallate were not detected. Overall flavan-3-ol metabolite excretion was equivalent to 8.1% of intake, however, urinary (epi)gallocatechin metabolites corresponded to 11.4% of (epi)gallocatechin ingestion while (epi)catechin metabolites were detected in amounts equivalent to 28.5% of (epi)catechin intake. These findings imply that (epi)catechins are highly bioavailable, being absorbed and excreted to a much greater extent than most other flavonoids. It is also evident that flavan-3-ol metabolites are rapidly turned over in the circulatory system and as a consequence C(max) values are not an accurate quantitative indicator of the extent to which absorption occurs.

Topics: Catechin; Chromatography, High Pressure Liquid; Flavonoids; Humans; Intestinal Absorption; Spectrometry, Mass, Electrospray Ionization; Tea

An extraction method on grape berry was optimized for the total flavan-3-ol content measurement with regard to the nature of the sample and the duration of its extraction. This extraction was performed for the first time on the whole pericarp. Flavan-3-ol extractions were achieved on Shiraz ripe samples of pericarp versus skin within different durations: the best results were obtained for the whole pericarp and 1 h duration. Therefore, this more convenient protocol was used to investigate the flavan-3-ol content at different stages through berry development, in parallel with the abundance of transcripts involved in their biosynthesis. Furthermore, flavan-3-ol extractions on pericarp analysis confirmed their presence in both pulp and skin. For the first time, the flavan-3-ol biosynthesis in pulp was demonstrated with both biochemical and transcriptomic analyses since the presence of leucoanthocyanidin reductase (LAR2) and anthocyanin reductase (ANR) transcripts was revealed by real-time PCR. In addition, the percentage of epigallocatechin was different in pulp and skin.

Topics: Anthocyanins; Catechin; Flavonoids; Fruit; Oxidoreductases; RNA, Messenger; Vitis

Cassava storage roots are an important staple food throughout the lowland humid tropics. However, cassava suffers from a poorly understood storage disorder, known as postharvest physiological deterioration (PPD), which constrains its exploitation. In an attempt to broaden the understanding of PPD, nine different cassava cultivars were analyzed for specific compounds accumulating during the process. The production of hydrogen peroxide (H(2)O(2)) is involved in the early stages of PPD in cassava roots. H(2)O(2) was quantified and localized histochemically at the tissue and cell level in deteriorating roots. This reactive oxygen species accumulated during the first 24 h after harvest, especially in the inner parenchymatic tissue. Three flavan-3-ols, (+)-catechin, (+)-catechin gallate, and (+)-gallocatechin, accumulated during the storage of cassava roots. However, these potential antioxidants cannot be related to early storage disorders or wound responses because they start to accumulate only after 4-6 days.

Topics: Catechin; Flavonoids; Food Preservation; Hydrogen Peroxide; Manihot; Phenols; Plant Roots; Species Specificity