Optimization of ultrasound extraction technology of DTD from Ageratina adenophora, and the preparation and characterization of nanoemulsions: Insecticidal activity and safety evaluation

Abstract

Due to the imperfect extraction process of 4,7-dimethyl-1-(propan-2-ylidene)− 1,4,4a,8a-tetrahydronaphthalene-2,6(1 H,7 H)-dione (DTD) and the nonconstruction of delivery systems, their practical application in the field of botanical pesticides is limited. To overcome these problems, ultrasound-assisted extraction technology was optimized using BoxBehnken design (BBD). The optimal ultrasound extraction conditions of DTD were as follows: time (39 min), solid to liquid ratio (1:31), and temperature (68 ℃). The extraction yield was 0.4528 ± 0.0182 %. Nanoemulsions (NEs) loaded with DTD were prepared and characterized, and the optimal formulation of DTD NEs was determined as follows: 1 wt% DTD, 1.5 wt% S-200, 1 wt% TW-80, and 96.5 wt% deionized water. The NEs prepared by the optimal formula had small contact angles and tension levels, indicating that they had good wetting properties. The larvicidal activity of DTD NEs is similar to that of azadirachtin EC. In the biosafety assessment, the DTD NE treatment group had low levels of cell apoptosis, the toxicity of the DTD NEs to earthworms was low, and the DTD NEs had no adverse effect on maize growth. Therefore, DTD NEs offer a high degree of biosafety. DTD NEs have the potential to serve as a safe, green alternative pesticide for IPM projects to control important agricultural pests.