Extraction, Nanoemulsion Development and the Toxicity of Cashew Nut Shell Liquid (CNSL) to Maize Weevil Sitophilus zeamais

Abstract

Cashew Nut Shell Liquid (CNSL) is a complex long branch and unsaturated phenolic compound with insecticidal potential. The main toxic component of CNSL is anacardic acid and its recovery amount is influenced by the extraction processes. Currently, mechanical extraction is the most effective and efficient technique for extracting CNSL from cashew nut shells. This study was conducted to observe the characteristics of CNSL as a botanical insecticide. This study aimed to determine toxicity and develop a nanoemulsion formulation for maize weevil (Sitophilus zeamais) control. Cashew nut shells were cut into 2-3 cm and heated at 80oC in a oven for 8 hours until moisture content reached 12.8%. In each process, 3 extractions were carried out using a mechanical centrifugal press (Honda GX 160 H1, Capacity: 0.6 L). Then the average CNSL extracted was calculated. An HPLC analysis was carried out to identify anacardic acid in CNSL extracts The results showed that CNSL extracted from cashew nut shell in this study ranged from 16.67 - 21.15%, with an average of 18.43%. The type of organic solvent used in CNSL formulation affected its toxicity against maize weevil. Compared to the methanol and ethanol solvents, acetone resulted in the highest toxicity of CNSL formulations with LC50 contact and feed respectively 32855 (2466 - 4036) ppm and 54750 (4287 - 6161) ppm. The CNSL nanoemulsions formulations has the potential to increase its toxicity against maize weevil. CNSL nanoformulation with heating treatment resulted in lower anacardic acid and lower toxicity against maize weevil by <60% compared with a similar formulation without heating.