Polyphenol Biosynthesis in Higher Plants — An Overview

3 Metabolites Formed by Oxidative Coupling of Galloyl Esters — Groups B 

This essay is dedicated to Professor T. S. Stevens, F. R. S., teacher, colleague and friend, on the occasion of his 80th birthday, 8th October 1980. 

Three classes of phenolic metabolite overwhelmingly predominate in the leaves of vascular plants (2). These are respectively  

Although the distribution and accumulation of phenolic constituents in different tissues of a particular plant may differ quite markedly in both a quantitative and qualitative sense the capacity for the synthesis of phenolic materials in the leaf of a plant is nevertheless frequently an accurate reflection of the synthetic capacity of the plant as a whole (e. g. stem, rhizomes, roots and fruit). It also provides the most convenient basis for the comparison of phenolic biosynthesis in different plants and plant families. Bate-Smith (2) used the pattern of distribution of the three principal dasses of-phenolic metabolites (i, ii, iii) in the leaves of plants as a taxonomic guide for the classification of plants. Many correlations were made but in particular he noted that between the presence of leucoanthocyanidins syn. proanthocyanidins) and a plant s woody habit of growth. Bate-Smith (2) also drew attention to the ability of particular plant families to metabolise phenols containing the vicinal-trihydroxyaryl (pyrogallol) group. These two synthetic capabilities were accorded the characters a and b respectively and plants were classified in the groups ab, oob, abo and oobo. 

The biosynthetic origin of the three classes of phenolic metabolite (i, ii, iii) is generally assumed to be associated with the development of a vascular character in plants and with the development of the ability to synthesise the structural polymer lignin by the diversion of L-phenyl-alanine and L-tyrosine (in the Gramineae) from protein synthesis. Plants 

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