Plant Toxins and their Applications

Abstract

Throughout the plant kingdom plants are subjected to mammalian herbivory, and insect and fungal infestations. During the course of evolution, they have produced a number of secondary compounds that are not directly involved with the basic metabolism but, by chance, serve with varying degrees of efficacy to enhance, reduce or destroy the plant’s palatability to phytophagous members of the animal kingdom. All angiosperms tend to accumulate concentrations of at least one type of secondary compound, whether it be alkaloid, flavonoid or terpenoid, but rarely concentrations of different classes of secondary compounds. Such defensive phytochemicals offer an explanation of what Feeny (1975) cited by Harborne (1988) considered a conspicuous non-event as to how the plant kingdom had managed to survive and dominate the earth against the predations of the numerically greatly superior phytophagous insects. Cruciferae members, for example, commonly contain a glucosinolate-myriosinase system that principally acts as a defence against herbivore insects (Blau et al., 1978; Chew, 1988). Yet another group of secondary compounds are responsible for disease resistance (see Section 4).