The origins of tannins and flavonoids in black-wattle barks and heartwoods, and their associated ‘non-tannin’ components

Abstract

The distributions of flavonoid, carbohydrate, amino acid and imino acid components in the leaves, twig bark, stem bark, root bark and heart-woods of the black-wattle tree were compared by paper chromatography after their isolation from specific portions of the tree. Wattle leaves contain mainly myricitrin, (+)-gallocatechin, an unknown myricetin glycoside and leuco-delphinidin tannins, together with smaller amounts of (+)-catechin, quercitrin and other flavonol glycosides. These are prominent in the twig bark, but decline progressively with age in the stem bark and are absent in root bark. The non-phenolic components of the mature stem bark were shown to be (+) pinitol, sucrose, glucose, fructose, L(-)-pipecolic acid, trans-4-hydroxy-L(-)-pipecolic acid, [alpha]-alanine, arginine, aspartic acid, glutamic acid, L(-)-proline, serine, a "steroid" alcohol and a long chain [beta]-diketone. Wattle bark and heartwood ''tannins'' consist of the analogues of closely related prototypes with common origins in the vascular tissues of the bark. Leaf "tannins" are superimposed on the bark components mainly during the initial stages of bark growth. Origins of the pipecolic acids and the transformations of carbohydrates in the sap- and heart-woods are discussed.