QSAR Study of Neonicotinoid Insecticidal Activity Against Cowpea Aphids by the MLR approach

A series of 30 neonicotinoid insecticides, bearing nitroconjugated double bond and five-membered heterocycles and nitromethylene compounds containing a tetrahydropyridine ring with exo-ring ether modifications, active against the cowpea aphids (Aphis craccivora), was analyzed using multiple linear regression (MLR) method. The semiempirical quantum chemical PM7 approach was employed for structure optimization. Structural descriptors were calculated for the minimum energy conformers and were related to the insecticidal activity (expressed as pLC₅₀ values) through genetic algorithm, using the multiple linear regression (MLR) approach. Several parameters were applied to check the internal and external model validation. The final MLR models demonstrated good statistical results and predictive power. The presence of more than 6-membered rings, a large number of rings containing secondary C(sp3) atoms, and/or higher values of strongest basic pK_a in the core structure of neonicotinoids are considered to decrease the insecticide activity.