25664-00-0

Upstream product

• 37064-31-6 catechin-(4α <*> 8)-catechin-(4α <*> 8)-catechin (C2) 
• 108-24-7 acetic anhydride 
• 23459-99-6 arecatannin A-1 
• 37064-30-5 procyanidin C₁ 
• 154-23-4 catechin 
• 480-18-2 taxifolin 

Relevant academic research and scientific papers

OLIGOMERIC FLAVAN-3-OLS FROM MEDICINAL WILLOW BARK

Chemical investigation of medicinal willow bark (Salix spp.) has led to the isolation and characterization of four dimeric (B1, B3, B6, B7) and five trimeric procyanidins.The structures of the triflavanoids were established on the basis of spectroscopic e

Proanthocyanidins and a phloroglucinol derivative from Rumex acetosa L.

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.

Studies in polyphenol chemistry and bioactivity. 4. Synthesis of trimeric, tetrameric, pentameric, and higher oligomeric epicatechin-derived procyanidins having all-4β,8-interflavan connectivity and their inhibition of cancer cell growth through cell cycle arrest

We report an improved synthesis of bis(5,7,3′,4′-tetra-O-benzyl)epicatechin 4β,8-dimer (3) from 5,7,3′,4′-tetra-O-benzylepicatechin (1) and 5,7,3′,4′-tetra-O-benzyl-4-(2-hydroxyethoxy)epicatechin (2) by replacing the previously employed Lewis acid, titanium tetrachloride, with the clay mineral Bentonite K-10. Under the same conditions, the benzyl-protected all-4β,8-trimer, -tetramer, and -pentamer were obtained regioselectively from their lower homologues, albeit in rapidly decreasing yields. Reaction of 2 with an organoaluminum thiolate generated from 2-mercaptobenzothiazole and trimethylaluminum followed by acetylation produced 3-O-acetyl -4-[(2-benzothiazolyl)thio]5,7,3′,4′-tetra-O-benzylepicatechin (12). Medium-sized protected oligomers with 4β,8-interflavan linkages are obtained in improved yields by using this compound as the electrophile and silver tetrafluoroborate as activator and are isolated by reversed-phase HPLC. Their deprotection by ester saponification followed by hydrogenolysis yielded the free procyanidins, which were characterized as their peracetates. The synthetic procyanidins are identical by normal-phase HPLC with fractions isolated from cocoa. The principle of chain extension by two members was demonstrated using a dimeric electrophile obtained by self-condensation of compound 12. Both the synthetic and natural pentamer 32 inhibit the growth of several breast cancer cell lines. Using the MDA MB 231 line, it was established that this outcome is based on the induction of cell cycle arrest in the G0/G1 phase. Subsequent cell death is more likely necrotic rather than apoptotic. Control experiments demonstrate that the polyphenol itself, rather than hydrogen peroxide potentially formed by its autoxidation, is the causative agent.

Carbon-14 biolabeling of (+)-catechin and proanthocyanidin oligomers in willow tree cuttings

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

PROANTHOCYANIDIN POLYMERS WITH ANTISECRETORY ACTIVITY AND PROANTHOCYANIDIN OLIGOMERS FROM GUAZUMA ULMIFOLIA BARK

Bioassay-guided fractionation of a crude extract of Guazuma ulmifolia bark led to the isolation of polymeric proanthocyanidins which inactivated cholera toxin (CT).The average degree of polymerization (DP) of the active compounds ranged from 14.4 to 32.0.The polymers consisted mainly of (-)-epicatechin units.In polymers of a representative fraction, the flavanol units were connected by 8> bonds and, less frequently, by 6> bonds.Inhibition of CT by tannins increased with Mr and conformation flexibility of the tannin molecule.Several known procyanidin oligomers were also isolated. 1H NMR shift rules to distinguish between 8> and 6> linked proanthocyanidin peracetates, that have been proposed for dimers, were extended to trimers and a tetramer.A further diagnostic shift parameter to determine the interflavanoid bonding position is presented and the conformation of oligomeric proanthocyanidin peracetates is discussed. - Key Word Index: Guazuma ulmifolia; Sterculiaceae; bark; proanthocyanidins; tannins; polymers; gel permeation chromatography; NMR; thiolytic degradation; (-)-epicatechin; peracetates; antisecretory activity.

Extensive High-Resolution Reverse 2D NMR Analysis for the Structural Elucidation of Procyanidin Oligomers

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

Linkage Isomerism in Trimeric and Polymeric 2,3-cis-Procyanidins

Four procyanidin trimers have been isolated and their structures unequivocally established as: epicatechin-(4β->8)-epicatechin-(4β->8)-catechin (5); epicatechin-(4β->6)-epicatechin-(4β->8)catechin (6); epicatechin-(4β->8)-epicatechin-(4β->6)-catechin (7); and epicatechin-(4β->8)-epicatechin-(4β->8)-epicatechin (13).The presence of the first three trimers in Pinus taeda phloem, and the isolation of both epicatechin-(4β->8)-4β-benzylepicatechin (9) and epicatechin-(4β->6)-4β-benzylthioepicatechin (10) from partial acid-catalyzed cleavage of the tannins from Pinus palustris phloem and Photinia glabrescens leaves, shows that linkage isomerism exists in natural oligomeric and polymeric procyanidins.A new system of nomenclature for proanthocyanidins is proposed.