Characterization of a novel (±)‐abscisic acid metabolite

By application of (±)‐abscisic acid and (±)‐[1‐ 14 C]‐abscisic acid to pea seedlings ( Pisum sativum L. cv. Kleine Rheinländerin), a new abscisic acid metabolite (Pisumic acid, PISA) could be isolated and structurally characterized by combined gas chromatography‐mass spectrometry. From data of exact mass determination, it is suggested that the metabolite has the tentative structure of 4′‐dihydroabscisic acid with a hydroxylated methyl group at C‐6′. That this could be evidence for an alternative pathway of abscisic acid metabolism which was suggested earlier by Walton et al. [Planta 112: 87–90 (1973)] is discussed.