Dihydroconiferyl alcohol as a gibberellin synergist in inducing lettuce hypocotyl elongation. An assessment of structure-activity relationships

Structure-activity relationships of the cotyledon factor wereexamined by testing the effect of various substances structurallyrelated to the cotyledon factor (dihydroconiferyl alcohol) ongibberellin-induced lettuce hypocotyl elongation. The biological activity of the cotyledon factor, 3-(4-hydroxy-3-methoxyphenyl)propan-1-ol, disappeared if the phenolic hydroxy group was maskedwith a methoxy or glucosyl group. Oxidation of the alcoholicgroup in the side chain to a carboxylic group decreased thebiological activity of the cotyledon factor. As to relationshipsbetween the biological activity and length of the alkyl sidechain, the propane type was found to be much more active thanthe methane, ethane or butane type. The presence of a C = Cbond in the alkyl side chain made the cotyledon factor biologicallyinactive. Some antioxidants of indole-3-acetic acid were alsoassayed for cotyledon factor-like activity, since the cotyledonfactor is a polyphenol. However, known antioxidants such asrutin, pyrocatechol, chlorogenic acid, caffeic acid and ferulicacid did not show cotyledon factor-like activity. From these results, structural requirements of the cotyledonfactor as a gibberellin synergist were discussed. (Received June 17, 1975; )