Quantitative structure-activity relationships (QSAR) of cinnamic acid birdrepellents

Plants have evolved an array of defense chemicals that inhibit the feeding of vertebrate herbivores and therefore have potential for agricultural and environmental applications to reduce feeding damage. we investigated the re lationship between structure and repellency for 14 derivatives of the plant secondary compound, cinnamic acid, using the feral pigeon (Columba livia) as the test species. The mechanism behind the repellent activity of these d erivatives is explained by a combination of four descriptors: heat of forma tion (Delta H-f), polarizability (XY and YY) and superdelocalizability (Sr) . All these parameters are electronic, indicating that changes in electroni c distribution within cinnamic acid structures are crucial for activity. Th is is the first published quantitative structure-activity model for avian r epellents, and as a result we can now begin to predict which cinnamic acid derivatives should make effective repellents. The full power of this model to aid the selection and screening of new repellents awaits further experim entation on both related compounds and other avian species. However, this m odeling approach promises to provide a more efficient and economic method f or prospecting chemical databases for new effective bird repellents.