BIOSYNTHESIS OF CAPSAICIN AND DIHYDROCAPSAICIN IN CAPSICUM FRUTESCENS

Capsaicin (N-(4-hydroxy-3-methoxybenzyl)non-trans-6-enamide) and 6,7-dihydrocapsaicin are found in approximately equal amounts in Capsicum frutescens. These alkaloids, isolated from the fruits of the plant 2 weeks after the administration of DL-phenyl-3-14C-alanine, were labeled solely on the methylene group of their vanillylamine residues. The administration of DL-tyrosine-3-14C afforded alkaloids with very low activity, l-Methionine-methyl-14C afforded radioactive alkaloids, and degradation of the dihydrocapsaicin indicated that all the activity was located on the methoxy group. No activity was found in the alkaloids when DL-mevalonic-2-14C acid or DL-leucine-l-14C were fed to the plant. However, radioactive capsaicin resulted when L-valine-U-14C was fed. Essentially all the activity was located at C-7, -8, -9, and -10 of the 8-methyl-6-nonenic acid moiety of the alkaloid. © 1968, American Chemical Society. All rights reserved.