Identification of glucopyranosyl‐β‐1,4‐glucopyranosyl‐β‐1‐ N ‐oxindole‐3‐acetyl‐ N ‐aspartic acid, a new IAA catabolite, by liquid chromatography/tandem mass spectrometry

[5‐ 3 H, 13 C 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‐β‐1,4‐glucopyranosyl‐β‐1‐ N ‐oxindole‐3‐acetyl‐ N ‐aspartic acid. The identification of glucopyranosyl‐β‐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.