Studies on the phenolic compounds of apple leaf tissue (Malus pumila Mill.) : a thesis presented in partial fulfilment of the requirements for the degree of Master of Horticultural Science in Plant Science

Abstract

THE PHENOLIC COMPOUNDS IN HIGHER PLANTS 1.1 The Natural Phenolic Compounds in Higher Plants A number of books dealing wholly or partly with the natural phenolic compounds have been published in recent years. A comprehensive treatment of phenolic compounds is presented in one of them (1). Specific discussion of the flavonoid group of phenolic compounds is also found elsewhere (2,3). In these references much of the literature on phenolic compounds is cited and reviewed.

1.1.1 The nature of phenolic compounds Substances which possess at least one aromatic ring bearing an hydroxyl substituent constitute the phenolic compounds. Several hundred such compounds are known in plants. They represent a number of groups of compounds including the simple monocyclic phenols, the flavonoids and their relatives, the xanthones, phenolic quinones, alkaloids and sterols, besides polymeric materials such as the tannins and lignins (4). Further discussion ot the natural phenolic compounds in this thesis will be largely confined to the two groups of monocyclic phenols (benzoic and cinnamic acid derivatives) and the flavonoid group of compounds. This recognises the relative importance of these three groups of phenolic compounds in plants in general and in the genus Malus in particular. While the flavonoid compounds constitute the largest group of natural phenols (4), the phenolic acids of the benzoic and cinnamic acid groups are present in variety in many plants (5). The following outline of each of these three groups will illustrate their nature. [From Introduction]