Biosynthesis of Capsaicinoids in Plants

Plant secondary metabolites have played a major role in providing special traits to different plants. Chilli peppers have their pungency due to the secondary metabolites called capsaicinoids, with capsaicin as the principal component. There are two pathways involved in its biosynthesis, one mediated by phenylpropanoid and the other by fatty acid metabolism. Capsaicin concentration in plants is influenced by genetic, environment and crop management factors. Its synthesis can however be enhanced by using elicitors. Capsaicin has been used as a food additive and in pharmaceutical applications as cancer preventive agent. Utilization of cell cultures for the production of biochemicals has been generally low due to low levels of product formation either in the plant or via tissue culture techniques. The media composition can be manipulated to increase culture yield that is on par or higher than mother plant. A comparative study of regulation of accumulation of capsaicin in suspension cultures, immobilized cell cultures and whole fruit gives us an insight about its biosynthetic requirements and efficiency. Efficient capsaicin production has been achieved by application of salicylic acid and calcium channel modulators in suspension cultures. Some of the techniques like virus-induced gene silencing have identified genes to be involved in capsaicinoid synthesis. The study of expression profiles of some genes has shown a relative correlation with pungency. The genome sequence information of hot pepper has been a very potent resource for clear understanding of capsaicinoid pathway, and it also helps study evolution of secondary metabolites in plants. This chapter is focused to giving all information related to capsaicinoids, biosynthetic pathways, factors affecting capsaicinoid content and their enhanced production by the use of elicitors.