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

Unnatural phaseic acid (U-PA) was identified by chiral GC as a minor c omponent 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 cel l suspension, d(6)-PA was obtained, establishing its origin from the e xogenously-added U-ABA. The major metabolite produced was identified a s U-7'-hydroxyabscisic acid (U-7'-HOABA) [d(5)-7'-HOABA from d(6)-U-AB A]. Confirmation of the assignments was obtained by HPLC/LC/CFSIMS ana lysis of the metabolite mixtures. This result corroborates a previous report of the formation of U-PA from racemic ABA in avocado mesocarp t issue.