A new, polar metabolite of abscisic acid (ABA) has been isolated from an aqueous extract of tomato plants. The compound is acidic, soluble in butanol and slightly soluble in acidic ethyl acetate. It is a major constituent of the products formed from (�)-[2-14C]abscisic acid and it occurs naturally.
The structure was determined by gas-liquid chromatography-mass spectrometry (g.l.c.-m.s.) and nuclear magnetic resonance (n.m.r.) spectrometry as the 1'-O-β-D-giucopyrairoside of abscisic acid (ABAGS). The glucosyl moiety was identified by g.l.c.-m.s. and a glucose oxidase test, the ABA by n.m.r. and g.l.c. Tests with α- and β-glucosidase proved inconclusive, but the signal of the anomeric proton in the �H n.m.r. spectrum showed the 8 Hz coupling of a β-glucoside. ABAGS can be methylated with redistilled diazomethane and, like the glucose ester of ABA (ABAGE), it is unstable in alkaline solutions.
Isolation and characterization of abscisic acid-deficient Arabidopsis mutants at two new loci