Precursor Biotransformation in Immobilized Placental Tissues of Capsicum frutescens Mill.:* II. Influence of Feeding Intermediates of the Capsaicinoid Pathway in Combination with L -Valine on Capsaicin and Dihydrocapsaicin Accumulation.

Increased yields of capsaicin and dihydrocapsaicin, major pungent principles of chilli pepper fruit, were
obtained when immobilized placental tissues of Capsicum frutescens were treated with intermediate metabolites
of the capsaicinoid pathway, i.e. I-phenylalanine, t-cinnamic acid, p-coumaric acid, caffeic acid,
ferulic acid and vanillylamine in combination with I-valine. Although vanillylamine and I-valine are the
nearest precursors to capsaicin, their addition to immobilized placenta did not significandy affect the
accumulation of capsaicin. Maximum capsaicin and dihydrocapsaicin accumulation was achieved on
p-coumaric acid + I-valine treatment. Maximum percentage of bioconversion was observed in culture
treated with t-cinnamic acid + I-valine. In nature, the ratio of the principle components - capsaicin and
dihydrocapsaicin - is about 2: 1. In immobilized placental tissues fed with precursors, the ratio of capsaicin
and dihydrocapsaicin varied between 2.2: 1 to 3.7: 1 compared with the ratio of 2: 1 present in natural
chilli pepper fruit. A productivity of 3.072 mg capsaicin/gDW/day was obtained by treating with p-coumaric
acid + I-valine, w~ was 514 % higher than that of chilli pepper fruit. These results successfully
demonstrate the use of placental tissue, the site of synthesis of capsaicin, to enhance yields of metabolites
in vitro using a combined precursor treatment.