IDENTIFICATION OF UNNATURAL PHASEIC ACID AS A METABOLITE DERIVED FROM EXOGENOUSLY ADDED (-)-ABSCISIC ACID IN A MAIZE CELL-SUSPENSION CULTURE

Unnatural phaseic acid (U-PA) was identified by chiral GC as a minor component of the metabolite mixture obtained from the medium of a maize cell suspension culture treated with unnatural (-)-(R)-abscisic acid (U-ABA). When U-[3',5',5',7',7',7']-hexadeutero-ABA was fed to the cell suspension, d(6)-PA was obtained, establishing its origin from the exogenously-added U-ABA. The major metabolite produced was identified as U-7'-hydroxyabscisic acid (U-7'-HOABA) [d(5)-7'-HOABA from d(6)-U-ABA]. Confirmation of the assignments was obtained by HPLC/LC/CFSIMS analysis of the metabolite mixtures. This result corroborates a previous report of the formation of U-PA from racemic ABA in avocado mesocarp tissue.