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Structure-antifeedant activity relationship of clerodane diterpenoids. Comparative study with withanolides and
R D Enriz1, H A Baldoni, M A Zamora
1Departamento de Química, Cátedra de Entomología, and Laboratorio de Alimentos, Facultad de Química, Bioquímica y Farmacia, Universidad Nacional de San Luis, Chacabuco y Pedernera, 5700 San Luis, Argentina. denriz@unsl.edu.ar
Abstract:
A structure-antifeedant activity relationship (SAR) study of clerodane diterpenoids was carried out. Attention was focused on the feeding-deterrent activities exhibited toward Tenebrio molitor by clerodane diterpenoids and withanolides. Azadirachtin was chosen as a reference compound. SAR studies on the clerodane compounds indicate that the stereoelectronic factors are more important than the hydrophobic aspects as determinants of antifeedant activity. A furan ring in the side chain and a carbonyl alpha,beta-unsaturated (or spiro-epoxide) group appear to be indispensable for the biological response. A conformational study indicate that the optimum interatomic distance between these moieties is a range between 9.5 and 10.5 A. In addition, a similar stereoelectronic response was found among withanolides and azadirachtin. On the basis of these results it is reasonable to imagine a closely related chemical mechanism for these compounds.