Recent Advances in the Chemistry of Condensed Tannins

Abstract

The presence of the procyanidins epicatechin-(4β-8)-catechin, epicatechin-{4β-6)-catechin, catechin-(4α-8)-catechin, epicatechin-(4β-8)-epicatechin-(4β-8)-catechin, epicatechin-(4β-6)-epicatechin-(4β-8)-catechin, and epicatechin-(4β-8)-epicatechin-(4β-6)catechin in tile phloem of Pinus taeda demonstrated heterogeneity in the location of the interflavanoid bonds in oligomeric procyanidins. Panial acid-catalyzed cleavage of polymeric procyanidins from Pinus taeda and Pinus palustris barks or Photinia glabrescens leaves gave both the epicatechin-(4β-8)-epicatechin- and epicatechin-(4β-6)-epicatechin-benzyl or phenyl sulfides, demonstrating isomerism in tile interflavanoid bond location in these polymers. Comparison of tile rates of acid-catalyzed cleavage of isomeric dimen showed that those compounds with a (4β-6) interflavanoid bond were more stable than compounds with a (4β-8) bond. Also, catechin-(4α-8)-catechin was more resistant to cleavage than either epicatechin-(4β-8)-catechin or epicatechin-(4β-8)-epicatechin when heated in the presence of excess phenylmethanethiol with acetic acid. The structures of condensed tannins and the stability of these polyrnen under acidic conditions are discussed.

Citation

Hemingway, Richard W.; McGraw, Gerald W.; Karchesy, J.J.; Foo, L.Y.; Porter, L.J. 1983. Recent Advances in the Chemistry of Condensed Tannins. Journal of Applied PoIymer Science: Applied Polymer Symposium 37(967-977