Abstract
Abscisic acid (ABA) is metabolized to phaseic acid (PA) via unstable 8'-hydroxy-ABA, and PA is converted to dihydrophaseic acid (DPA) and epi-DPA. Quantitation of the metabolites is important, since concentration of ABA is regulated not only by biosynthesis but also metabolism. However, deuterated analogs of the metabolites as internal standards have not been reported, while hexa-deuterated ABA is an internal standard of ABA. We report preparation of the deuterated metabolites.
[3',3',5',5'-2H4]PA was easily prepared, but the label was lost during methylation by diazomethane. Preparation of [7',7',7'-2H3]PA was tried using the equilibrium between PA and 8'-hydroxy-ABA. PA kept in NaOD for 26 days was treated with NaOH to give [7',7',7'-2H3]PA. The label was persistant to diazomethane, and at pH 3-8. [7',7',7'-2H3]DPAs were prepared by reduction of [7',7',7'-2H3]PA. These deuterated metabolites enable precise quantitation of the ABA metabolites.
