- Carbon-14 biolabeling of (+)-catechin and proanthocyanidin oligomers in willow tree cuttings
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Proanthocyanidin polymers, oligomers, and the structurally related monomer (+)-catechin were labeled by incorporation of radioactive precursors in shoots of willow tree (Salix caprea L.). [1-14C]Acetate and [U-14C]- phenylalanine pre
- Deprez, Stephanie,Mila, Isabelle,Scalbert, Augustin
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Read Online
- Proanthocyanidins and a phloroglucinol derivative from Rumex acetosa L.
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From the ethyl acetate soluble fraction of an acetone-water extract of the aerial parts of Rumex acetosa L. (Polygonaceae), a variety of monomeric flavan-3-ols (catechin, epicatechin, epicatechin-3-O-gallate), A- and B-type procyanidins and propelargonidins (15 dimers, 7 trimers, 2 tetramers) were isolated with 5 so far unknown natural products. Dimers: procyanidin B1, B2, B3, B4, B5, B7, A2, epiafzelechin-(4β→8)-epicatechin, epiafzelechin-(4β→8)-epicatechin-3-O-gallate (new natural product), epiafzelechin-(4β→6)-epicatechin-3-O-gallate (new natural product), epiafzelechin-3-O-gallate-(4β→8)-epicatechin-3-O-gallate, B2-3′-O-gallate, B2-3,3′-di-O-gallate, B5-3′-O-gallate, and B5-3,3′-di-O-gallate. Trimers: procyanidin C1, epiafzelechin-(4β→8)-epicatechin-(4β→8)-epicatechin (new natural product), epicatechin-(4β→8)-epicatechin-(4β→8)-catechin, cinnamtannin B1, cinnamtannin B1-3-O-gallate (new natural product), tentatively epicatechin-(2β→7, 4β→8)-epiafzelechin-(4α→8)-epicatechin (new natural product), and epicatechin-3-O-gallate-(4β→8)-epicatechin-3-O-gallate-(4β→8)-epicatechin-3-O-gallate. Tetramers: procyanidin D1 and parameritannin A1. All compounds were elucidated by ESI-MS, CD spectra, 1D- and 2D-NMR experiments as free phenols or peracetylated derivatives and, in part, after partial acid-catalysed degradation with phloroglucinol. A more abundant proanthocyanidin polymer was also isolated, purified and its chemical composition studied by 13C NMR. In addition a so far unknown phloroglucinolglycoside (1-O-β-d-(2,4-dihydroxy-6-methoxyphenyl)-6-O-(4-hydroxy-3,5-dimethoxybenzoyl)-glucopyranoside) was isolated.
- Bicker,Petereit,Hensel
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experimental part
p. 483 - 495
(2010/06/15)
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- Synthetic studies of proanthocyanidins. Part 2: Stereoselective gram-scale synthesis of procyanidin-B3
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A stereoselective synthesis of procyanidin-B3, a condensed catechin dimer, is described. Condensation of benzylated catechin with various 4-O-alkylated flavan-3,4-diol derivatives as an electrophile in the presence of a Lewis acid led to protected procyanidin-B3 and its diastereomer. In particular, the reaction using (2R,3S,4S)-3-acetoxy-5,7,3′,4′-tetrabenzyloxy-4-(2″- ethoxyethoxy)flavan as an electrophile in the presence of TMSOTf at -78°C afforded octa-O-benzylated procyanidin-B3 with high levels of stereoselectivity and in excellent isolation yields. Furthermore, we succeeded in a stereoselective gram-scale synthesis of protected procyanidin-B3.
- Saito, Akiko,Nakajima, Noriyuki,Tanaka, Akira,Ubukata, Makoto
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p. 7829 - 7837
(2007/10/03)
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- Extensive High-Resolution Reverse 2D NMR Analysis for the Structural Elucidation of Procyanidin Oligomers
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The structures of the procyanidin dimers catechin-(4α-8)-catechin and catechin-(4α-6)-catechin were proved by spectroscopic means.To distinguish between the two possible interflavonoid linkages, it is necessary to assign all the quaternary aromatic carbon signals.How these assignments can be made through two-dimensional NMR spectroscopy is described. - Keywords: 2D NMR 1H NMR 13C NMR Structural analysis Proanthocyanidins Catechin dimers Tannins
- Balas, Laurence,Vercauteren, Joseph
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p. 386 - 393
(2007/10/02)
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- CHARACTERIZATION AND TRYPSIN INHIBITOR ACTIVITY OF PROANTHOCYANIDINS FROM VICIA FABA
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In a chemical investigation epicatechin, epigallocatechin, the procyanidins B-1, B-3 and B-4, and the prodelphinidins gallocatechin-(4α,8)-catechin, gallocatechin-(4α,8)-epicatechin and gallocatechin-(4α,8)-epigallocatechin have been isolated from the testa of faba beans and characterized by means of spectroscopic methods.Proanthocyanidin samples were compared for their trypsin inhibitory activity.The results suggest that the degree of polymerization, the number of phenolic hydroxyl groups and the 2,3-stereochemistry of the constituent units affect remarkably the strength of the inhibition.
- Helsper, Johannes P. F. G.,Kolodziej, Herbert,Hoogendijk, Johanna M.,Norel, Arend van
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p. 1255 - 1260
(2007/10/02)
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- PROCYANIDINS AND POLYPHENOLS OF LARIX GMELINI BARK
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Key Word Index - Larix gmelini; Pinaceae; bark; catechins; procyanidins; biflavonoids; larixinol.Methanol extracts of Larix gmelini bark yielded (-)-epiafzelechin, (+)-catechin and (-)-epicatechin, dimeric procyanidins B-1, B-2, B-3 and B-4 and oligomeric procyanidins.Chemical degradation of the oligomers using toluene-α-thiol and acetic acid showed the oligomers to have flavan-3-ol terminal units possessing either the 2,3-trans (catechin) or 2,3-cis (epicatechin) stereochemistry, with the former predominating.Likewise the extension units were shown to consist of flavan-3-ol units with 2,3-trans or 2,3-cis stereochemistry in roughly equal proportion.The average degree of oligomerization was calculated as 6-7 and the number average molecular weight as 1700-2000.The structure of the residual procyanidins remaining in the bark after methanol extraction is also briefly commented upon.Larixinol is shown to have an unusual spirobiflavonoid structure and a pathway of biogenesis is proposed.
- Shen, Zhaobang,Haslam, Edwin,Falshaw, Christopher P.,Begley, Michael J.
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p. 2629 - 2636
(2007/10/02)
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- SYNTHESIS AND CHARACTERIZATION OF PROCYANIDIN DIMERS AS THEIR PERACETATES AND OCTAMETHYL ETHER DIACETATES
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Key Word Index - Biomimetic synthesis; procyanidins B1-B8; 3,4-cis-biflavanoid; all--bi--(+)-catechin; 1H NMR parameters. Condensation of (2R,3S,4R or S)-leucocyanidin or the 5,7,3',4'-tetramethyl ether of (2R,3R,4S)-leucocyanidin with flavan-3-ols yielded dimeric flavanoids which were converted to their octamethyl ether diacetates, or the deca-acetates for the 2,3-trans-procyanidin series.Comparison is made of the 1H NMR spectra of the deca-acetate and octamethyl ether diacetate derivatives which lead to useful diagnostic shift parameters characteristic of their structures.Condensation afforded a novel biflavanoid with a 3,4-cis-configuration and a triflavanoid of 'mixed' stereochemistry.
- Kolodziej, Herbert
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p. 1209 - 1216
(2007/10/02)
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- HETEROGENEITY OF INTERFLAVANOID BOND LOCATION IN LOBLOLLY PINE BARK PROCYANIDINS
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Procyanidins B-1 B-3 and B-7 were obtained from Pinus taeda phloem in yields of 0.076, 0.021 and 0.034percent of unextracted dry wt.Procyanidins B-1 and B-7 were produced in relative yields of 2.4:1 by biosynthetically patterned synthesis from catechin and loblolly pine tannins.Partial acid-catalysed thiolytic cleavage of loblolly pine phloem tannins produced (2R,3S,4S)-2,3-cis-3,4-trans-3,3',4',5,7-pentahydroxy-4-phenylthioflavan and both (2R,3R,4R)-2,3-cis-3,4-trans-3,3'4',5,7-pentahydroxy-4-flavan and (2R,3R,4R)-2,3-cis-3,4-trans-3,3',4',5,7-4-flavan in ratios of 3 : 1 demonstrating regio-isomerism of the interflavanoid linkage in the polymeric procyanidins of loblolly pine bark.Key Word Index - Pinus taeda; Pinaceae; loblolly pine; bark; phloem; procyanidins; condensed tannins; interflavanoid linkage; regio-isomerism.
- Hemingway, Richard W.,Karchesy, Joseph J.,McGraw, Gerald W.,Wielesek, Richard A.
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p. 275 - 282
(2007/10/02)
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- DIMERIC FLAVANOLS OF Juniperus sabina. I.
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Procyanidins B2, B3, and B4 have been isolated from Juniperus sabina for the first time.On the basis of chemical transformations and the PMR spectroscopy of their decaacetates, and absolute configurations of the asymetric centers of each of the halves of the molecules of the dimer have been determined: 2R, 3R, 4R for the "upper" half and 2R, 3R for the "lower" half of B2, 2R, 3S, 4S for the "upper" half and 2R, 3S, for the "lower" half of B3; and 2R, 3S, 4S for the "upper" half and 2R, 3R for the "lower" haalf of B4.
- Pashinina, L. T.,Abil'kaeva, S. A.,Sheichenko, B. I.
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p. 282 - 287
(2007/10/02)
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