Biosynthesis of mustard oil glucosides: conversion of phenylacetaldehyde oxime and 3-phenylpropionaldehyde oxime to glucotropaeolin and gluconasturtiin.

Apart from certain amino acids none of the nitrogenous intermediates involved in the biosynthesis of mustard oil glucosides have, untl now, been determined. Results consistent with the hypothesis — amino acids → aldehyde oximes → mustard oil glucosides — are presented for glucotropaeolin and gluconasturtin. Administration of dl-[2-¹⁴C]phenylalanine and [1-¹⁴C]phenylacetaldehyde oxime to Tropaeolum majus L. shoots resulted in a greater incorporation of the tracer from the latter into the aglycone moiety of glucotropaeolin; incorporation of ¹⁴C from phenylacetaldehyde oxime into the aglycone was without randomization. Radioactive phenylacetaldehyde oxime was isolated from T. majus shoots which were fed dl-[2-¹⁴C]phenylalanine. The extent of conversion of ¹⁴C into the aglycone of gluconasturtin was similar when 3-phenyl[1-¹⁴C]propionaldehyde oxime and dl-2-amino-4-phenyl[2-¹⁴C]butyric acid were fed to Nasturtium officinale R. Br. There was no randomization of labelled carbon in gluconasturtin aglycone derived from 3-phenylpropionaldehyde oxime.