Dimeric Ellagitannins Research Articles

ChemInform Abstract: Total Syntheses of Laevigatins A and E.

We describe the first total syntheses of two ellagitannins, laevigatins A and E. Laevigatin A comprises a 2,3-O-(S)-hexahydroxydiphenoyl-α-D-glucose unit, whose anomeric oxygen atom forms a dehydrodigalloyl ester. Laevigatin E is a dimeric ellagitannin with structural motifs similar to those of laevigatin A. A recently developed method for synthesizing C–O digallates allowed the synthesis of more than 1 g of laevigatin A. The abundant supply allowed the synthesis of laevigatin E, an achievement that implies that more complex ellagitannins could be accessible.

Metabolism of strawberry mono- and dimeric ellagitannins in rats fed a diet containing fructo-oligosaccharides

PurposeWe investigated the effects of dietary supplementation with strawberry extracts rich in ETs and fructo-oligosaccharides (FOS) on the intestinal microbiota and the formation of bacterial metabolites in the distal intestine, as well as the absorption of ET metabolites and antioxidant status in rats.MethodsRats were allocated into six groups of eight animals each and fed for 4 weeks with a control diet (group C), a control diet supplemented with FOS (group C + FOS) or modifications of these diets, in which a monomeric or dimeric ET-rich extract was added (groups ME and ME + FOS or DE and DE + FOS, respectively).ResultsThe extract addition, the FOS addition and their interaction significantly affected the total and selected bacterial counts in the caecal digesta (all P < 0.005). The total bacterial count was the highest in group C + FOS, lower in group DE and the lowest in group ME + FOS (10.6, 10.3 and 8.52 log cells/g, respectively; P ≤ 0.05). The total caecal content of ET metabolites was higher in the ME and ME + FOS group than in the DE and DE + FOS group, respectively (67.8 and 89.5 vs. 13.0 and 18.0 µg/g, respectively; P < 0.001). The total plasma concentration of ET metabolites was higher in the ME + FOS and DE + FOS group than in the ME group (248 and 281 vs. 8.13 ng/mL, respectively; P < 0.001).ConclusionsETs of the monomeric ET-rich extract are more prone to intestinal breakdown than those of the dimeric ET-rich extract, and absorption of their metabolites can be increased by dietary FOS; however, together, they evoke strong antibacterial activity.

Total Syntheses of Laevigatins A and E

AbstractWe describe the first total syntheses of two ellagitannins, laevigatins A and E. Laevigatin A comprises a 2,3‐O‐(S)‐hexahydroxydiphenoyl‐α‐D‐glucose unit, whose anomeric oxygen atom forms a dehydrodigalloyl ester. Laevigatin E is a dimeric ellagitannin with structural motifs similar to those of laevigatin A. A recently developed method for synthesizing C–O digallates allowed the synthesis of more than 1 g of laevigatin A. The abundant supply allowed the synthesis of laevigatin E, an achievement that implies that more complex ellagitannins could be accessible.

Isolation of tannins from Agrimonia eupatoria, Lythrum salicaria and Geum urbanum and their influence on the release of elastase from stimulated human neutrophils – structure-activity studies

Tannin rich plant materials are traditionally used as antiinflammatory and astringent agents. However, there are limited studies on chemical composition of those plant materials, as well as on bioactivity of their constituents. The aim of the study was to isolate the dominating tannin compounds from Lythri herba, Gei urbani radix and Agrimoniae eupatoriae herba and to investigate their influence on the release of elastase from stimulated human neutrophils. The structure-bioactivity relationship was also investigated. The isolation was carried out using column chromatography with Diaion HP-20 and Toyopearl HW40F eluted with MeOH-H2O and acetone-H2O solvent system. The assignment of chemical structures of isolated compounds was performed using 1D and 2D NMR experiments and by MS. If possible the comparisons to the literature were made. The elucidation led to the identification of salicarinin A, B and C, vescalagin and castalagin from Lythri herba, agrimoniin from A. eupatoriae herba and pedunculagin, sthenophylanin A, stachyurin and gemin A and G from G. urbani radix. All compounds were investigated as elastase release inhibitors in human neutrophils' model. Compounds were tested at concentrations of 1,5 and 20 mM. It revealed that only non-cyclic dimeric ellagitannins such as gemins A and G, agrimoniin and salicarinins A, B and C inhibit the release of elastase from neutrophils by 20 – 50% compared to control. Non-cyclic dimeric ellagitannins displayed similar properties in used model as possitive control – quercetin. The current study has shown that investigated plant materials are a rich source of tannins. The inhibitory activity towards the elastase release of dimeric ellagitannins should be considered as important contribution of those compounds to the antiinflammatory activity of plant materials from which they were isolated.

Size and molecular flexibility affect the binding of ellagitannins to bovine serum albumin.

Binding to bovine serum albumin of monomeric (vescalagin and pedunculagin) and dimeric ellagitannins (roburin A, oenothein B, and gemin A) was investigated by isothermal titration calorimetry and fluorescence spectroscopy, which indicated two types of binding sites. Stronger and more specific sites exhibited affinity constants, K1, of 10(4)-10(6) M(-1) and stoichiometries, n1, of 2-13 and dominated at low tannin concentrations. Weaker and less-specific binding sites had K2 constants of 10(3)-10(5) M(-1) and stoichiometries, n2, of 16-30 and dominated at higher tannin concentrations. Binding to stronger sites appeared to be dependent on tannin flexibility and the presence of free galloyl groups. Positive entropies for all but gemin A indicated that hydrophobic interactions dominated during complexation. This was supported by an exponential relationship between the affinity, K1, and the modeled hydrophobic accessible surface area and by a linear relationship between K1 and the Stern-Volmer quenching constant, K(SV).

Protein-phenolic interaction of tryptic digests of β-lactoglobulin and cloudberry ellagitannin.

LC-ESI-MS was applied to investigate interaction reactions between a dimeric ellagitannin, sanguiin H-6, isolated from cloudberries (Rubus chamaemorus) and peptides of β-lactoglobulin (β-Lg). Three peptides, LIVTQTMK (m/z 934), ALPMHIR (m/z 838), and IPAVFK (m/z 674) were isolated from enzymatic (trypsin) digestion of β-Lg. Oxidation of the peptides with and without sanguiin H-6 was monitored by LC-ESI-MS for up to 7 days. Sanguiin H-6 showed radical scavenging activities toward oxidation of the selected peptides. An interaction product was found with sanguiin H-6 and peptide LIVTQTMK by using MS and supported by sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE). An observable (haze) but unstable interaction product of sanguiin H-6 was seen with peptide ALPMHIR, but no detectable interaction products were seen with peptide IPAVFK. A higher proportion of sanguiin H-6 toward the amount of peptide might allow for further characterization of these interaction products.

Genotoxicity and cytotoxicity evaluation of oenothein B and its protective effect against mitomycin C-induced mutagenic action

The natural product oenothein B (OeB), a dimeric macrocyclic ellagitannin, has a wide range of biological activities, such as antioxidant, anti-inflammatory, anti-viral, antifungal, and antitumor. However, investigations concerning its genotoxicity have not been carried out. This study assessed the cytotoxicity, genotoxicity, and protective effects of oenothein B using in vitro SOS-Inductest and in vivo mouse bone marrow micronucleus (MN) assay through oral and intraperitonial routes. In both assays oenothein B did not produce genotoxic effects in any of doses tested; in contrast, cytotoxic effect in cells was detected only in mice groups treated by both routes and exposed for 24 and 48h. Antigenotoxic and anticytotoxic activities of oenothein B were evaluated using both assays in combination with mitomycin C (MMC), a bioreductive alkylating agent. In the MN assay, a significant reduction was observed in MN frequency in all groups co-treated with MMC and OeB compared to those which received only MMC. Anticytotoxicity was observed in mice groups exposed to OeB and MMC for 24 and 48h. In the SOS-Inductest, oenothein B failed to show antigenotoxic and anticytotoxic effects; thus, it undoubtedly showed an in vivo protective activity against primary DNA damage induced by mitomycin C.

Variation of chemical composition of Epilobium angustifolium during fermentation

Infusion from fermented Epilobium angustifolium L. herb (Ivan tee) is traditionally consumed in Russia for the treatment of stomach ulceration, gastritis, and sleeping disorders. It has been used in folk medicine to treat a variety of ailments such as benign prostate hyperplasia and the associated problems of micturition. Flavonoids and tannins, particularly oenothein B, dimeric hydrolyzable ellagitannin seemed to be responsible for these activities.

Oenothein B, a Cyclic Dimeric Ellagitannin Isolated from Epilobium angustifolium, Enhances IFNγ Production by Lymphocytes

Oenothein B is a polyphenol isolated from Epilobium angustifolium and other plant sources, which has been reported to exhibit immunomodulatory properties. Oenothein B is known to activate myeloid cells and induce the production of IL-1 and other cytokines. However, its effects on lymphocytes are unknown. In this report, we show that oenothein B stimulated innate lymphocytes, including bovine and human γδ T cells and NK cells, resulting in either increased CD25 and/or CD69 expression. We also demonstrate that oenothein B enhanced the production of interferon-γ (IFNγ) by bovine and human NK cells alone and in combination with interleukin-18 (IL-18), a response not observed with other commonly studied polyphenols. Furthermore, we demonstrate that oenothein B enhanced the production of IFNγ by human T cells. Since IFNγ contributes to antitumor, antibacterial, and antiviral cell responses, these data suggest an additional mechanism that could account, at least in part, for the immune enhancing properties of oenothein B.

Determination of Macrocyclic Ellagitannin Oenothein B in Plant Materials by HPLC‐DAD‐MS: Method Development and Validation

Oenothein B (OeB) is a dimeric macrocyclic ellagitannin occurring mainly in the genus Oenothera. In the literature no validated HPLC method for quantification of this compound has been reported. To develop and validate an efficient HPLC method for quantification of OeB in plant materials. Extraction conditions of OeB from plant material were optimised. Then the first validated HPLC method for quantification was developed. We have shown that ultrasonic-assisted extraction at 40 °C in 15 min using water are the most optimal conditions for OeB extraction. We have quantified OeB in several plant materials belonging to Oenotheraceae family. The lowest amount of OeB was present in Circaea lutetiana herb (27.64 ± 0.26 mg/g) and the highest was quantified in Epilobium hirsutum aerial parts (72.91 ± 1.38 mg/g). The first HPLC method for quantification of OeB in plant materials was developed and validated. We also for the first time optimised the extraction conditions for OeB.

Two new phenolic glucosides and an ellagitannin from the leaves of Castanopsis sclerophylla

In the course of a chemotaxonomical study of Castanopsis species (Fagaceae), detailed investigation of the leaves of C. sclerophylla led to isolation of three new phenolic compounds together with 62 known compounds. The structures of the new compounds were elucidated as 2-O-galloyl-O-4,6-(S)-valoneoyl-d-glucose (1), 6-O-galloyl-1-O-vanilloyl-β-d-glucose (2), and 4″-O-galloylchestanin (3) by means of spectroscopic analyses and enzymatic hydrolysis with tannase. Comparison with other Castanopsis species indicated that C. sclerophylla characteristically accumulates chlorogenic acid and a dimeric ellagitannin, rugosin E. Triterpene hexahydroxydiphenoyl esters, which are major constituents of C. cuspidata var. sieboldii, C. hystrix, and C. fissa were not detected.

SOILLESS CULTURES FOR PHARMACEUTICAL USE AND BIODIVERSITY CONSERVATION

Soilless cultures are nowadays an important tool for both (i) large scale synthesis of pharmaceutically active products, and for (ii) ex situ conservation of endemic and/or endangered plants that are also of horticultural importance. (i) Epilobium hirsutum explants were grown on both solid- and shaken liquid-medium, for multiplication and for greater biomass production, respectively. Secondary metabolites extracted from the biomass thus obtained were mainly polyphenols (galloylglucose and monomeric and dimeric ellagitannins), which are pharmaceutically important in prostate adenoma treatment, among others. Seedlings' dry biomass production increased from 1.5 g DW L -1 to 22 g DW L -1 after 15 days when nodes/inocula were grown on shaken liquid-medium, in light, and using different phytohormonal conditions. Secondary metabolites yield (polyphenols) of seedlings was equal to or higher (under some conditions) than for intact plants grown normally, in soil, under normal conditions. (ii) In vitro conservation on solid media resulted in a collection of 12 species that are endemic and/or endangered for Europe, and 7 species for Romania, respectively. Included in this collection are: Dianthus spiculifolius, D. nardiformis, D. henteri, D. glacialis subsp. gelidus, D. haematocalyx subsp. pindicola, D. seguieri, D. sternbergii, Achillea pyrenaica, Paradisea liliastrum. Dianthus petraeus subsp. simonkaianus was the species with the best multiplication rate (110 shoots/inoculum).

Fatty Acid Synthase Inhibitors from Geum japonicumThunb. var. chinense

Bioassay-guided fractionation of the MeOH extract of Geum japonicum Thunb. var. chinense using the fatty acid synthase inhibition assay led to the isolation of a new dimeric ellagitannin, gemin G (1), together with six known compounds, gemin A (2), casuarinin (3), pedunculagin (4), potentillin (5) , tellimagrandin II (6), and ellagic acid (7). Their structures were determined on the basis of spectroscopic analyses. Compounds 1-7 displayed strong inhibitory activities on fatty acid synthase with IC(50) values in the range of 0.21-41.4 microM. Compounds 1-4 exhibited significant antioxidant activities higher than vitamin C in the ORAC assay. Compounds 1 and 2 also showed weak cytotoxic effects on BGC-823 cell.

Flavonol glucuronides and C-glucosidic ellagitannins from Melaleuca squarrosa

Two flavonoids and three ellagitannins, squarrosanins A, B, and C, were isolated from the leaves of Melaleuca squarrosa. The flavonoids were characterized structurally as kaempferol-3- O-(2″- O-galloyl)-glucuronide and herbacetin-3- O-glucuronide, while the ellagitannins were characterized as monomeric and dimeric C-glucosidic ellagitannins by application of spectroscopic and chemical methods. The antioxidant effect of the polyphenolic constituents of the M. squarrosa leaves was also examined in vitro, and C-glucosidic tannins including oligomers were shown to be more effective radical scavengers against 1,1-diphenyl-2-picrylhydrazyl (DPPH) than flavonoids and ordinary ellagitannins.

Rubusuaviins A-F, Monomeric and Oligomeric Ellagitannins from Chinese Sweet Tea and Their .ALPHA.-Amylase Inhibitory Activity

Six new ellagitannins herein, rubusuaviins A-F, were isolated from the aqueous acetone extract of Chinese sweet tea (Tien-cha, dried leaves of Rubus suavissimus S. LEE) together with seven known tannins. Rubusuaviin A was characterized as 1-O-galloyl-2,3-O-(S)-HHDP-4,6-O-(S)-sanguisorboyl-beta-D-glucopyranose. Rubusuaviins B, C, and E are dimeric, trimeric, and tetrameric ellagitannins, respectively, in which the sanguisorboyl groups were connected ellagitannin units. Rubusuaviins D and F were desgalloyl derivatives of rubusuaviins C and E, respectively. The inhibition of alpha-amylase activity by rubusuaviins and related ellagitannins was compared. Ellagitannins with beta-galloyl groups at the glucose C-1 positions showed stronger inhibition compared with the alpha-galloyl and desgalloyl compounds. The molecular weight of these compounds was not important for the inhibition of alpha-amylase activity.

Enzymology of Gallotannin and Ellagitannin Biosynthesis

AbstractFor Abstract see ChemInform Abstract in Full Text.

Induction of neutral endopeptidase activity in PC-3 cells by an aqueous extract of Epilobium angustifolium L. and oenothein B

An aqueous extract of Epilobium angustifolium and its main compound oenothein B (OeB), a dimeric macrocyclic ellagitannin, are specifically able to induce the neutral endopeptidase (NEP) in prostate cancer cells. The angiotensin-converting enzyme (ACE) is not influenced. Additionally, a weak but statistically significant inhibition of cell proliferation is observed. Simultaneous treatment of the cells with arabinosylcytosine and the extract as well as the OeB, leads to an additional enhancement of NEP activity. Taking into account the role of this peptidase in prostate cancer progression, our results might offer a pharmacological explanation for the use of Epilobium in folk medicine.

Compounds fromEpilobium angustifoliumInhibit the Specific Metallopeptidases ACE, NEP and APN

Willow herb (Epilobium angustifolium L.) extracts showed inhibitory activity against the metallopeptidases: neutral endopeptidase (NEP), angiotensin-converting enzyme (ACE), and aminopeptidase N (APN). A bioassay-guided fractionation led to the isolation of several flavonoids and phenolic acids and an ellagitannin. The dimeric macrocyclic ellagitannin oenothein B inhibited the neutral endopeptidases in a dose-dependent manner with IC50 = 20 microM. Other polyphenols showed weaker activity but their synergistic activity cannot be excluded. Taking into account the role of these peptidases in prostate diseases, the results may partly support and explain the use of Epilobium extracts in folk medicine.

Seasonal Variation in the Content of Hydrolyzable Tannins, Flavonoid Glycosides, and Proanthocyanidins in Oak Leaves

Oaks have been one of the classic model systems in elucidating the role of polyphenols in plant-herbivore interactions. This study provides a comprehensive description of seasonal variation in the phenolic content of the English oak (Quercus robur). Seven different trees were followed over the full course of the growing season, and their foliage repeatedly sampled for gallic acid, 9 individual hydrolyzable tannins, and 14 flavonoid glycosides, as well as for total phenolics, total proanthocyanidins, carbon, and nitrogen. A rare dimeric ellagitannin, cocciferin D2, was detected for the first time in leaves of Q. robur, and relationships between the chemical structures of individual tannins were used to propose a biosynthetic pathway for its formation. Overall, hydrolyzable tannins were the dominant phenolic group in leaves of all ages. Nevertheless, young oak leaves were much richer in hydrolyzable tannins and flavonoid glycosides than old leaves, whereas the opposite pattern was observed for proanthocyanidins. However, when quantified as individual compounds, hydrolyzable tannins and flavonoid glycosides showed highly variable seasonal patterns. This large variation in temporal trends among compounds, and a generally weak correlation between the concentration of any individual compound and the total concentration of phenolics, as quantified by the Folin-Ciocalteau method, leads us to caution against the uncritical use of summary quantifications of composite phenolic fractions in ecological studies.

Ellagitannin biosynthesis: laccase-catalyzed dimerization of tellimagrandin II to cornusiin E in Tellima grandiflora

A new laccase (EC 1.10.3.2)-type phenol oxidase has been purified from leaves of Tellima grandiflora (fringe cups, Saxifragaceae) that catalyzed the O 2-dependent coupling of two tellimagrandin II molecules to the dimeric ellagitannin, cornusiin E.