title: Electrolytic reduction of abscisic acid methyl ester and its free acid.
abstract: Abscisic acid (ABA, 1), a plant hormone, has electrophilicity derived almost entirely from the side-chain, 3-methylpenta-2,4-dienoic acid. The electrochemical property of ABA was investigated by analysis of its cathodic reaction. ABA methyl ester (1-Me) was reduced at a peak potential of -1.6 V to give a unique and unstable bicyclic compound (5-Me) as a major product at pH 3 and 7. This finding showed that an electron was absorbed in the conjugated dienecarboxyl group, and that C-5 with a high electron density attacked C-2' through an intramolecular nucleophilic addition. At pH 10, in addition to 5-Me, a compound 4-Me was formed by isomerization of 5-Me under alkaline conditions. For a cathodic reaction of ABA at pH 3 and 7, compound 5 was a major product as well as in the case of ABA methyl ester. However, at pH 10, a dimer (6) with an epoxy group, 1'-deoxy-ABA (7) and other compounds were formed instead of compounds 4 and 5. Compounds 4 and 5 were biologically inactive, suggesting the importance of the electrophilic side-chain of ABA for biological activity.
authors.affiliation: Graduate School of Agriculture, Kyoto University, Kyoto 606-8502, Japan. hirai@kais.kyoto-u.ac.jp
authors.forename: Nobuhiro
authors.initials: N
authors.lastname: Hirai
authors.forename: Kumiko
authors.initials: K
authors.lastname: Iwami
authors.forename: Mari
authors.initials: M
authors.lastname: Horiuchi
authors.forename: Kenji
authors.initials: K
authors.lastname: Kano
authors.forename: Yasushi
authors.initials: Y
authors.lastname: Todoroki
authors.forename: Hajime
authors.initials: H
authors.lastname: Ohigashi
mesh_terms: D000040:Abscisic Acid / Q000737:chemistry* / Q000378:metabolism / Q000494:pharmacology; D004572:Electrolysis; D004952:Esters; D018525:Germination / Q000187:drug effects; D018545:Lactuca / Q000187:drug effects / Q000254:growth & development; D010084:Oxidation-Reduction; D018515:Plant Leaves / Q000187:drug effects / Q000254:growth & development; D036226:Seedlings / Q000187:drug effects / Q000254:growth & development; D012639:Seeds / Q000187:drug effects / Q000254:growth & development
chemical_list: D004952:Esters; D000040:Abscisic Acid