68200-27-1Relevant academic research and scientific papers
PROANTHOCYANIDIN POLYMERS WITH ANTISECRETORY ACTIVITY AND PROANTHOCYANIDIN OLIGOMERS FROM GUAZUMA ULMIFOLIA BARK
Hoer, Michaela,Heinrich, Michael,Rimpler, Horst
, p. 109 - 120 (2007/10/03)
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.
Proanthocyanidins from Lotus Corniculatus
Foo,Newman,Waghorn,Mcnabb,Ulyatt
, p. 617 - 624 (2007/10/03)
The chemical structure of the purified proanthocyanidin polymers of Lotus corniculatus was analysed by 13CNMR and by mild acid catalysed degradation in the presence of excess of phloroglucinol. The NMR data showed that the polymer was partially glycosidated with a number average Mr in the range 1800-2100 (six to seven flavanoid units). The products from phloroglucinol scission reaction indicated the extender flavan units to consist mostly of epicatechin (67%) and epigallocatechin (30%), with minor amounts of catechin and epiafzelechin units, which were linked together predominantly by C-4/C-8 interflavanoid bonds. The polymer chains were terminated mostly by catechin (83%) and, to a lesser extent, by epicatechin (16%). Copyright
THIOLYSIS OF BIRCH BARK PROCYANIDINES: STRUCTURAL DEPENDENCE IN FORMATION OF 2,3-CIS-3,4-CIS-FLAVAN-4-BENZYLTHIOETHERS FROM PROCYANIDINS
Kolodziej, Herbert
, p. 1671 - 1674 (2007/10/02)
Thiolytic studies of the birch bark procyanidins, epicatechin-(4β->8)-catechin (B1), epicatechin-(4β->6)-catechin (B7) and epicatechin-(4β->8)-epicatechin-(4β->8)-catechin, provided, in addition to known β-thioethers, evidence for the presence of the first 2,3-cis-3,4-cis-flavan-4-benzylthioethers.Their formation is dependent on the 2,3-stereochemistry of the 'lower' terminal flavan unit and apparently on the relative lability of the interflavanoid linkage.By contrast, epicatechin-(4β->8)-epicatechin (B2), epicatechin-(4β->6)-epicatechin (B5) and epicatechin-(4β->8)-epicatechin-(4β->8)-epicatechin (C1), afforded only 2,3-cis-3,4-trans-flavan-4-benzylthioethers.
4-CARBOXYMETHYL FLAVAN-3-OLS AND PROCYANIDINS FROM DAVILLIA DIVARICATA
Hwang, Tieh-Horng,Kashiwada, Yoshiki,Nonaka, Gen-Ichiro,Nishioka, Itsuo
, p. 279 - 282 (2007/10/02)
A series of flavan-3-ols and procyanidins, processing a carboxymethyl group, and a procyanidin tetramer have been isolated from the fern, Davallia divaricata.The structures were characterized on the basis of chemical and spectral evidence.
PROCYANIDIN POLYMERS OF DOUGLAS FIR BARK: STRUCTURE FROM DEGRADATION WITH PHLOROGLUCINOL
Foo, Lai Yeap,Karchesy, Joseph J.
, p. 3185 - 3190 (2007/10/02)
Reaction of the condensed tannin polymers of Douglas fir inner bark with phloroglucinol yielded catechin, epicatechin, procyanidin B-2, catechin-(4α->2)-phloroglucinol, epicatechin-(4β->2)-phloroglucinol, the novel compound epicatechin-(4α->2)-phloroglucinol and 1,3-di-(2,4,6-trihydroxyphenyl)-1-(3,4-di-hydroxyphenyl)-propan-2-ol.Also isolated were epicatechin-(4β->8)-epicatechin-(4β->2)-phloroglucinol, epicatechin-(4β->6)-epicatechin-(4β->2)-phloroglucinol, and three other novel phloroglucinol adducts, catechin-(4α->8)-epicatechin-(4β->2)-phloroglucinol, epicatechin-(4β->8)-epicatechin-(4β->8)-epicatechin-(4β->2)-phloroglucinol and epicatechin-(4β->6)-epicatechin-(4β->8)-epicatechin-(4β->2)-phloroglucinol.The results suggest that the configuration of the extender units is almost exclusively 2,3-cis, while the terminal units are mixed, with 2,3-cis slightly predominating.The C-4 to C-8 interflavonoid linkage predominates over the C-4 to C-6 linkage by a 4:1 ratio. Key Word Index Pseudotsuga menziesii; Pinaceae; Douglas fir; procyanidin; degradation; phloroglucinol-adducts.
Tannins and Related Compounds. Part 13. Isolation and Structures of Trimeric, Tetrameric, and Pentameric Proanthicyanidins from Cinnamon
Nonaka, Gen-ichiro,Morimoto, Satoshi,Nishioka, Itsuo
, p. 2139 - 2145 (2007/10/02)
A proanthocyanidin trimer, two tetramers, and a pentamer have been isolated in their free phenolic forms from cinnamon, the bark of Cinnamomum zeylanicum (Lauraceae).Partial acid-catalysed degradation of these tannins with phenylmethanethiol, in conjunction with 1H- and 13C-n.m.r. analysis, has unequivocally established their structures as epicatechin-(4β->8, 2β->7)epicatechin-(4α->8)-epicatechin (5); epicatechin-(4β->8)epicatechin-(4β->8, 2β->7)-epicatechin-(4α->8)-epicatechin (6); epicatechin-(4β->6)-epicatechin-(4β->8, 2β->7)-epicatechin-(4α->8)-epicatechin (7); and epicatechin-(4β->8)-epicatechin-(4β->8)epicatechin-(4β->8, 2β->7)-epicatechin-(4α->8)-epicatechin (8).
