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Substituent effects of cis-cinnamic acid analogues as plant growh inhibitors

Nishikawa, Keisuke, Fukuda, Hiroshi, Abe, Masato, Nakanishi, Kazunari, Taniguchi, Tomoya, Nomura, Takashi, Yamaguchi, Chihiro, Hiradate, Syuntaro, Fujii, Yoshiharu, Okuda, Katsuhiro, Shindo, Mitsuru
Phytochemistry 2013 v.96 pp. 132-147
Spiraea, allelochemicals, growth retardation, hydrophobicity, lettuce, phytotoxicity, root growth
1-O-cis-Cinnamoyl-β-d-glucopyranose is one of the most potent allelochemicals that has been isolated from Spiraea thunbergii Sieb by Hiradate et al. It derives its strong inhibitory activity from cis-cinnamic acid (cis-CA), which is crucial for phytotoxicity. By preparing and assaying a series of cis-CA analogues, it was previously found that the key features of cis-CA for lettuce root growth inhibition are a phenyl ring, cis-configuration of the alkene moiety, and carboxylic acid. On the basis of a structure–activity relationship study, the substituent effects on the aromatic ring of cis-CA were examined by systematic synthesis and the lettuce root growth inhibition assay of a series of cis-CA analogues having substituents on the aromatic ring. While ortho- and para-substituted analogues exhibited low potency in most cases, meta-substitution was not critical for potency, and analogues having a hydrophobic and sterically small substituent were more likely to be potent. Finally, several cis-CA analogues were found to be more potent root growth inhibitors than cis-CA.