The Formation of Polyphenols in Trees

The polyphenolic components in the cambial tissues of several eucalypt species are mainly C6 compounds in the form of ellagitannins; shikimic acid is also present in appreciable quantities (Hillis & Carle, 1958, 1962; W. E. Hillis, unpublished work). When the cambial tissues of eucalypts are injured in the growing season, a faint-brown liquid commonly exudes and dries to a brown or brown-red, brittle, semi-transparent solid. This astringent exudate, known as kino, contains very largely C15 compounds, usually in the form of leuco-anthocyanins (Hillis & Carle, 1960, 1963; W. E. Hillis, unpublished work). Consequently, it appears that acetate units become available in relatively larger amounts in damaged cambium to enable the formation of the A ring of the C15 flavonoid components of kino. Attempts to indicate the processes governing this increased availability have been made with the use of enzyme inhibitors and are described in the present paper. Several types of hnkages between the leucoanthocyanin units of condensed tannins have been proposed (Hathway, 1962; Hergert, 1962; Swain, 1962). Some of these linkages have resulted during the study of the behaviour of model compounds under conditions in vitro. Similar linkages may also form in vivo when polyphenols remain in plant tissues for long periods and during their isolation and purification. However, little attention has been given to the possibility that these linkages may supplement or modify those originally formed. An examination of polymerized polyphenols within a short period of their formation should yield information on the nature of 'primary' linkages. The definition of such linkages would assist the determination of the extent of linkages formed subsequently. Kinos can be collected within 5 days of formation (Hillis & Hasegawa, 1963) and are suitable material for study. This present work reports an investigation of the kino ofEucalyptus sieberiana F. Muell. (family Myrtaceae), which is very largely composed of polymerized leuco-delphinidin. The polymers formed by monomeric leuco-delphinidin (3',4',5,5',7'-pentahydroxyflavan-3,4-diol) and the related gallocatechin under conditions in vitro and those isolated from plant tissue have been studied previously (Hathway, 1958; Roberts, 1957). * Part I: Hillis & Hasegawa (1963). EXPERIMENTS AND RESULTS