Submitted to: Phytochemistry
Publication Type: Peer reviewed journal
Publication Acceptance Date: 9/20/1995
Publication Date: N/A
Citation: Interpretive Summary: Rain during harvest can cause preharvest sprouting in wheat resulting in lower grain quality. Sprouting damaged wheat is discounted, which causes economic losses to producers. We are determining the chemical features of a plant hormone, abscisic acid (ABA), which is an effective sprouting inhibitor. Our objective is to identify the critical features of the molecule required for sprouting inhibition in order to obtain information to design even more potent sprouting inhibitors. In this report we have examined the hydroxyl group at carbon 1' of the molecule. We have converted the hydroxyl group to a methyl ether, and then tested the inhibitory activity of the modified molecule. Our results show that this modification of the hydroxyl group causes a small reduction in inhibitory activity, indicating that this region of the molecule can be slightly modified without major activity loss. This new information can now be used by plant scientists to investigate how ABA molecule interacts with cellular proteins to block sprouting and to synthesize more effective sprouting inhibitors.
Technical Abstract: C-1' methyl ethers of abscisic acid and their methyl esters, as well as the methyl ethers of the acetylenic analogue of methyl ABA, were synthesized through an enantioselective route, giving a series of optically active, new C-1' substituted analogues with known stereochemistry. In a wheat embryo germination inhibition assay, the (-)-enantiomer of O-methyl ABA shows high activity, comparable with (+)- and (-)-ABA, whereas the (+)-enantiomer of the C-1'-hydroxy methyl ether is less active. In a wheat seedling transpiration assay both analogues exhibit weak activity although the (+)-ABA-like analogue is more potent than its enantiomer. The antitranspirant response increases over time, which may indicate that the analogue is being metabolized to ABA in vivo.