Insecticidal activity of eucalyptus oil nanoemulsion with karanja and jatropha aqueous filtrates

The aim of this study was to utilize the aqueous filtrate of de-oiled karanja (Pongamia glabra) and jatropha (Jatropha curcas) cakes left after extracting oil for preparing biodiesel to enhance the activity of eucalyptus oil (Eucalyptus globulus) as a pesticide by making a nanoemulsion for the control of Tribolium castaneum, a secondary pest of stored grains. The aqueous filtrate obtained, from the solid cake possessing insecticidal properties was used in place of distilled water to enhance the shelf life of eucalyptus oil for a longer period of time. The eucalyptus oil nanoemulsion containing karanja and jatropha aqueous filtrate with concentrations of 300 and 1500 ppm gave 88-100% mortality rates against T castaneum adults within 24 h. The LC50 values recorded for the nanoemulsions with and without the aqueous filtrate were 0.1646 mg/l and 5.4872 mg l(-1),indicating greater toxicity for the nanoemulsion containing aqueous filtrate. The GC MS analysis also indicated the degradation of the marker compound, i.e., 1, 8-cineole, in both types of nanoemulsions, i.e., with and without the aqueous filtrate. Analysis with ATR-FTIR also confirmed the presence of 1,8-cineole in the nanoemulsion containing the aqueous filtrate. The nanoemulsion formulation with the lowest average particle size, 77 nm, was chosen for extensive efficacy trials against T castaneum. It was found that the loss of eucalyptus oil by volatilization was stabilised in the nanoemulsion containing the aqueous filtrate. (C) 2014 Elsevier Ltd. All rights reserved.