Purine alkaloids, cytokinins, and purine-like neurotoxin alkaloids

Abstract

Purine alkaloids, such as caffeine, theobromine, theophylline, 7-methylxanthosine, and theacrine, are produced in several plant species including tea, coffee, cacao, and maté. The major route of caffeine biosynthesis is the xanthosine → 7-methylxanthosine → 7-methylxanthine → theobromine → caffeine pathway. Two hypotheses concerning the ecological roles of caffeine in plants, chemical defense and allelopathic function theories, have been proposed. Genetically modified plants of agriculturally important plant species have been obtained. One is construction of coffee plants in which caffeine production is suppressed, and the others are caffeine-producing tobacco and chrysanthemum plants which resist infection by fungal and insect pests. The impact of caffeine on human health is discussed, and, in addition to purine alkaloids, cytokinins, adenine-derived phytohormones, and the neurotoxin alkaloids, saxitoxin and tetrodotoxin are also described briefly.