IDENTIFICATION OF GLUCOPYRANOSYL-BETA-1,4-GLUCOPYRANOSYL-BETA-1-N-OXINDOLE-3-ACETYL-N-ASPARTIC ACID, A NEW IAA CATABOLITE, BY LIQUID-CHROMATOGRAPHY TANDEM MASS-SPECTROMETRY

[5-H-3, C-13(6)]Indole-3-acetic acid was fed to immature pericarp segments from fruits of tomato (Lycopersicon esculentum Mill., cv. Moneymaker), resulting, after 24 h of incubation, in five radiolabelled peaks when analysed by reversed-phase high-performance liquid chromatography with radiocounting. The fractions were numbered in order of decreasing polarity. Fractions 4 and 5 had earlier been shown to contain indole-3-acetyl-N-aspartic acid and indole-3-acetyl-O-glucose. Based on results from strong alkaline hydrolysis, it had been concluded that fractions 1 and 3 contain an amide conjugate with a modified indole ring. This paper presents data supporting the structure of the labelled compounds in fractions 1 and 3 to be diastereomers of glucopyranosyl-beta-,1,4-glucopyranosyl-beta-1-N-oxindole-3-acetyl-N-aspartic acid. The identification of glucopyraoosyl-beta-1-N-oxindole-3-acetyl-N-aspartic acid in fraction 2 is also reported. These structures were elucidated by liquid chromatography/frit fast atom bombardment tandem mass spectrometry.