Biosynthesis of Characteristic Flavours in Plants

Abstract

The characteristic flavours in plant- leaf alcohol, cis-3-hexenol, and leaf aldehyde, trans-2-hexenal, are widely distributed in fresh leaves, vegetables and fruits and are responsible for the odor characteristic of the leaf. Also, both are found in some insect excretions as functioning attractants and repellents. The investigation of leaf alcohol has been carried out by Takei and Ohno et al. since 1938; from 1957, we have been studying leaf alcohol and leaf aldehyde from a number of angles: synthetic chemistry, natural products chemistry, and plant biochemistry. Recently, we focused our attention on the biosynthesis of leaf alcohol and leaf aldehyde and have demonstrated the biosynthetic pathway using Thea sinensis leaves. We know now that leaf alcohol and aldehyde are produced from cis-3-hexenal. This C6-compound, cis-3-hexenal and the C12-compound, 11 - formyl -cis- 9 -undecenoic acid, are biosynthesized from linolenic acid by enzymatic oxygenative splitting through the addition of oxygen to the double bond between C-12 and C-13. This C12-fragment isomerizes to give 11 - formyl - trans-10-undecenoic acid, traumatic half aldehyde, which is known as the “Wound Hormone”. © 1981, The Society of Synthetic Organic Chemistry, Japan. All rights reserved.