Biosynthesis of alkaloids and betalains

Margaret F. Roberts Dieter Strack an(d Michael Wink  

Keywords alkaloid biosynthesis alkaloid genes nicotine tropane alkaloids pyrrolizidine alkaloids benzylisoquinoline alkaloids monoterpene indole alkaloids ergot alkaloids acridone alkaloids purine alkaloids taxol betalains 

The biogenesis of alkaloids has been studied from the beginning of the past century, first to determine their structures and subsequently to study their biosynthesis in plants (Mothes et al, 1985). Detailed h)q)otheses of alkaloid 

Alkaloids are an integral part of many medicinal plants and have enjoyed a long and important history in traditional medicine. Our first drugs originated from plant extracts and some important contemporary pharmaceuticals are still either isolated from plants or structurally derived from natural products (Seigler, 1998 Wink, 2000, 2007 Dewick, 2002 van Wyk and Wink, 2004). 

The majority of alkaloids have been found to be derived from amino acids, such as tyrosine, phenylalanine, anthranilic acid, tryptophan/tryptamine, ornithine/arginine, lysine, histidine and nicotinic acid (Fig. 2.1). However, alkaloids maybe derived from other precursors such as purines in case of caffeine, terpenoids, which become aminated after the main skeleton has been synthesized i.e. aconitine or the steroidal alkaloids, are found in the Solanaceae and Liliaceae. Alkaloids may also be formed from acetate-derived polyketides, where the amino nitrogen is introduced as in the hemlock alkaloid, coniine. 

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