ABSTRACT
Ohta (1962) and then Fujiwake et al. (1980) reported that capsaicinoids were localized in the vacuole of the epidermal cells of placentas and septa, and the accumulation of capsaicinoids reached the maximum level when the size of the fruits reached the maximum. Experiments using radioactive substances revealed that capsaicinoids were biosynthesized from the two arms; the aromatic component from L-phenylalanine to vanillylamine, and C9-C11 branched-chain
fatty acid moieties from L-valine or L-leucine (Bennet and Kirby, 1968; Leete and Louden, 1968) (Figure 5.1). The intensive work of Iwai was particularly important for the establishment of the fundamental aspects of the biosynthetic pathway of capsaicinoids (Iwai, 1986). The pathway proposed for the biosynthesis of the vanillylamine moiety of capsaicinoids from L-phenylalanine is as follows: L-phenylalanine, trans-cinnamic acid, trans-p-coumaric acid, trans-caffeic acid, trans-ferulic acid, vanillin and vanillylamine. In the pathway of biosynthesis of capsaicinoids, the last step of condensation of vanillylamine and fatty acids is expected to be important, but the enzyme for that step has not so far been purified. Suppressive or stimulative factors are also unknown so far.
