Big Chemical Encyclopedia

Chemical substances, components, reactions, process design ...

Articles Figures Tables About

Catechin dimers

In a few cases, the synthesis was directed towards well-defined oligomers (dimers, trimers, etc.). The synthesis of bis(5,7,3, 4 -tetra-0-benzyl)-EC 4/1,8-dimer from 5,7,3, 4 -tetra-0-benzyl-EC and 5,7,3, 4 -tetra-0-benzyl-4-(2-hydroxyethoxy)-EC was described by Kozikowski et al. [41]. This compound exhibited the ability to inhibit the growth of several breast cancer cell fines through the induction of cell cycle arrest in the Gq/Gi phase. Analogously, procyanidin-B3, a condensed catechin dimer, has been obtained through condensation of benzylated catechin with various 4-0-alkylated flavan-3,4-diol derivatives in the presence of a Lewis acid. This reaction led to protected procyanidin-B3 and its diastereomer. In particular, octa-O-benzylated procyanidin-B3 has been produced with high levels of stereoselectivity and in excellent isolation yields [42]. [Pg.247]

The electrophilic primary and secondary quinones undergo addition of nucleophiles, including flavonoids. For instance, nucleophilic addition of catechin to its enzymatically generated quinone yielded a catechin dimer in which the catechin moieties are linked through a C6 C8 biphenyl linkage. This B-type dehydrodicatechin further oxidized to yellow pigments. Additional dehydrodicatechins arise from radical coupling of the catechin semi-quinones formed by retro-disproportionation, in which the catechin moieties are linked... [Pg.288]

Recent studies performed using this method have shown that flavanol bitterness decreases from monomer to trimer. Epicatechin was perceived more bitter than catechin and the C4-C6-linked catechin dimer more bitter than other procyanidin dimers with C4-C6 linkages. This may be due to the higher lipophilic character of these molecules facilitating their diffusion to the gustatory receptor. Bitterness of procyanidin fractions in 5% ethanol decreased with their... [Pg.304]

Saito, A. et al.. Synthetic studies of proanthocyanidins. Highly stereoselective synthesis of the catechin dimer, procyanidin B-3, Biosci. Biotechnol. Biochem., 66, 1764, 2002. [Pg.610]

Kondo, K. et al.. Conversion of procyanidin B-t5 pe (catechin dimer) to A-type evidence for abstraction of C-2 hydrogen in catechin during radical oxidation, Tetrahedron Lett., 41,485, 2000. [Pg.614]

Unlike some classes of polyphenols such as flavonols and flavones, flavanols are almost always present in the nonglycosylated form. Removal of glycoside from flavonoids, usually necessary before the transport across the intestinal barrier, is not required in the case of flavanols [Scalbert and Williamson, 2000]. The absorption of procyanidins by the small intestine was investigated by studying 14C-( + )-catechin, dimer, trimer, and procyanidin polymers permeation through Caco-2 cell cultures [Deprez et al., 2001]. There was little difference in permeability between monomer, dimmer, and trimer, based on the measurement of radioactivity present on the basal side of the cultures, whereas the permeability of the polymers was 10 times lower. The authors reported the absence of catechin metabolism but did not determine whether the radioactivity measured on the basal side of the cultures was from the parent dimers to polymers or from their products of degradation or metabolites, which could have resulted from instability of the parent compounds in the culture... [Pg.57]

Catechin, dimer B3, trimer Rats C2, and purified polymers (urine)... [Pg.62]

Another membrane property physically affected by flavonoids is the surface potential. Working with liposomes composed of PC and PS, we found that (—)-epicatechin and certain procyanidins (dimer to hexamer) decreased liposome surface potential. This effect relied on both, procyanidin concentration and number of monomeric units [Verstraeten et al., 2003]. On the other hand, when liposomes were composed exclusively of PC, it was found that (—)-epi-catechin dimers Al and B2, and the trimers A and C2 increased liposome surface potential in a concentration-dependent manner [Verstraeten et al.,... [Pg.112]

Colored adducts in which the anthocyanin and the flavanol are linked by a carboxy-methine bridge, have also been identified, in addition to colorless carboxy-methine-linked catechin dimers (Chapter 9B), in model solutions containing (-i-)-catechin, malvidin-3-glucoside and glyoxylic acid (Es-Safi et al. 2003). [Pg.448]

Precursors. The precursors for this reaction are anthocyanins, flavanols or flavanols containing a vinyl residue at C-8 (i.e., 8-vinylflavanols). 8-Vinylflavanols could arise from the cleavage of flavanol-ethyl-flavanol oligomers or from the dehydration of the flavanol-ethanol adduct formed after the attack of aldehyde cation to the flavanol (Chapter 9B). Saucier et al. (1997) have supported evidence for this precursor when detecting an ion corresponding to vinyl-catechin from the fragmentation of ethyl-linked catechin dimers under ESI-MS in positive or negative mode. [Pg.451]

Figure 4 examples of products obtained by aldehyde-induced reactions ethyl-linked catechin dimer (1), ethyl-linked catechin-malvidin-3-glucoside adduct (2), ethanoic acid-linked catechin-dimer (3)... [Pg.131]

Cruz L, Bras NF, Teixeira N, Mateus N, Ramos Ml, Dangles O, De Freitas V (2010) Vinylcatechin dimers are much better copigments for anthocyanins than catechin dimer procyanidin B3. J Agric Food Chem 58 3159-3166... [Pg.1788]

Two teracacidol-catechin dimers linked (4)ff->8) and (4)ff- 6) have been synthesized, but these compounds have not been reported as natural products (27, 28). A melacacidol-(4a- 6)-melacacidol dimer isolated from the heartwood of Prosopis glandulosa (mesquite) occurs in low concentration together with the oxidatively coupled flavan-3-ols described previously (174). Foo (103) has recently isolated a melacacinidin-(4a->6)-isomelacacidin dimer from Acacia melanoxylon, the first natural product that has the 2i ,3i ,4i -(2,3-d5-3,4-c/5)-stereochemistry. However, only its 2R,3R,4S (2y3-cis-3,4-t ans) diastereoisomer was obtained by synthesis. [Pg.619]

Ahn B-Z, Gstirner F 1971 Uber Catechin Dimer der Eichenrinde. Arch Pharmaz 304 666-673... [Pg.636]

Ahn B-Z, Gstirner F 1973 Uber Catechin-dimere der Eichenrinde III. Arch Pharm (Weinheim) 306 338-346... [Pg.685]


See other pages where Catechin dimers is mentioned: [Pg.132]    [Pg.289]    [Pg.296]    [Pg.298]    [Pg.299]    [Pg.304]    [Pg.58]    [Pg.294]    [Pg.227]    [Pg.158]    [Pg.353]    [Pg.90]    [Pg.98]    [Pg.112]    [Pg.101]    [Pg.136]    [Pg.161]    [Pg.447]    [Pg.407]    [Pg.194]    [Pg.66]    [Pg.67]    [Pg.103]    [Pg.420]    [Pg.613]    [Pg.619]    [Pg.701]    [Pg.701]    [Pg.701]    [Pg.702]    [Pg.364]   
See also in sourсe #XX -- [ Pg.120 ]




SEARCH



Catechine

Catechins

Gallocatechin-catechin dimer

© 2024 chempedia.info