Potent Production of Capsaicinoids and Capsinoids by Capsicum Peppers

Abstract

The fundamental structure of capsinoids is a fatty acid ester with vanillyl alcohol, whereas in capsaicinoids, a fatty acid amide is linked to vanillylamine. To clarify the relationship between their biosynthesis in Capsicum plants, we carried out an in vivo tracer experiment using stable isotopically labeled putative precursors. Liquid chromatography-tandem mass spectrometry was used to measure the uptake of isotopes into metabolites after injection of the labeled precursors into intact fruits of a pungent cultivar, Peru, and a non-pungent cultivar, CH-19 Sweet. Labeled vanillylamine was incorporated into capsaicinoids in both cultivars. While labeled vanillyl alcohol was incorporated into capsinoids in both cultivars, the accumulation of intact capsaicinoids in Peru was suppressed by over 60% after administration of vanillyl alcohol. In Peru, labeled vanillin was converted to both vanillylamine and, in 5-fold excess, vanillyl alcohol. Moreover, labeled vanillin was converted exclusively to vanillyl alcohol in CH-19 Sweet. These data are consistent with the incorporation of labeled vanillin into capsaicinoids and capsinoids in both cultivars. We conclude that pungent cultivars are highly potent producers of vanillyl alcohol that is incorporated into capsinoids and that biosynthesis of capsinoids is catalyzed by capsaicin synthase.

Evidence of capsaicin synthase activity of the Pun1-encoded protein and its role as a determinant of capsaicinoid accumulation in pepper

“…The expression profile of Pun1 correlates with pepper pungency and the deletion or down-regulation of the Pun1 gene results in a decreased accumulation of capsaicinoids. In addition to capsaicinoids, Pun1 has been reported to control capsinoid synthesis in nonpungent pepper cultivars [ 14 , 15 ].…”

“…However, Pun1 is considered a putative gene because its encoded enzyme has not been biochemically analyzed, even though functional genomics studies indicate that Pun1 is responsible for the acylation of vanillylamine and vanillyl alcohol in Capsicum sp . [ 13 - 15 ]. In the present study, we used protoplasts and anti-Pun1 antibodies to verify that the Pun1 gene is actually involved in the crucial step of capsaicin biosynthesis.…”

Formation of long-chain N-vanillyl-acylamides from plant oils

“…For example, the chili pepper cultivar Peru contained only 14 μg/g dry weight fruit of VA, which accounted for about 1/150 of its total capsaicinoid content. 6) In our previous study, the highest LCNVA content (ca. 2400 μg/g) in Capsicum oleoresin was around 40% of its capsaicin content.…”

Identification of a Novel Mutant <i>pAMT</i> Allele Responsible for Low-pungency and Capsinoid Production in Chili Pepper: Accession ‘No. 4034’ (<i>Capsicum chinense</i>)

“…pAMT encodes the enzyme that catalyses the conversion of vanillin to vanillylamine (Curry et al, 1999). The loss-of-function in pAMT supresses production of vanillylamine from vanillin, and vanillyl alcohol is produced instead, which results in a significant increase in capsinoid content (Han et al, 2013;Kobata et al, 2013;Sutoh et al, 2006). Therefore, the pamt mutation is the key factor in genetic improvements in terms of pungency and capsinoid content in Capsicum breeding programs.…”