The formation of phenolic substances in Eucalyptus gigantea and Eucalyptus sieberiana

Abstract

The distribution of phenolic substances in the woody tissues and kino of E. gigantea and E. sieberiana is described. Ellagic acid is present to a varying degree in all woody and phloem tissues of these species. The ellagitannins present include juglanin, corilagin and, in the phloem of young E. sieberiana, [beta]-glucogallin also. The ratio of free to combined ellagic acid is low in the sapwood, higher in the phloem and higher still in the heartwood. The amount of free and combined ellagic acid is higher in the heartwood than in the sapwood. Catechin is present in the bark and sapwood of both species and in the cambium of E. sieberiana. Shikimic acid and i3-glucogallin is present in the cambium and phloem of young E. sieberiana. Traces of polymerized leucodelphinidin and leucocyanidin were present in all woody tissues examined. The substances that are removed from the methanol extract of heartwood with light petroleum, ether and ethyl acetate do not give a red color when heated with butanol-hydrochloric acid. The kinos from these species contain polymerized leucodelphinidin and traces of leucocyanidin and ellagic acid. On acid-treatment gallic acid and further amounts of ellagic acid are liberated, and, in addition, phloroglucinol and other substances not present in the woody tissues. Present evidence indicates that kino and the phenolic constituents in woody tissues are formed in situ from starch, glycosides and translocated carbohydrate.