Characterization of Dihydrophaseic Acid 4′-O- β -D-Glucopyranoside as a Major Metabolite of Abscisic Acid

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Abstract
(±)-[2-14C]abscisic acid (ABA) and [2-14C]dihydrophaseic acid (DPA) fed to tomato shoots were converted into an acidic, polar conjugate that was hydrolysed (1 M HCl, 100°C) to D-glucose and DPA. The tetraacetylmethyl ester of the metabolite was isolated by high performance liquid chromatography as colourless crystals (m.p. 81-84°). N.m.r. spectra showed the presence of a β-glucosidic linkage (J 7 Hz, CDCl3; 8 Hz, D5 pyridine) between C-4' of DPA and C-1 of glucose. Mass spectra of the 0-acetylmethyl ester of the conjugate, and also of material biosynthesized from [1'-18O]ABA, showed that the glucoside is at C-4' of DPA. The abbreviation 'DPAGS' is proposed.