Amylose inclusion complexes as emulsifiers for garlic and asafoetida essential oils for mosquito control

Authors: Muturi, Ephantus; Hay, William; Behle, Robert; Selling, Gordon

Submitted to: Insects
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/8/2019
Publication Date: 10/11/2019
Citation: Muturi, E.J., Hay, W.T., Behle, R.W., Selling, G.W. 2019. Amylose inclusion complexes as emulsifiers for garlic and asafoetida essential oils for mosquito control. Insects. 10(10):337. https://doi.org/10.3390/insects10100337.
DOI: https://doi.org/10.3390/insects10100337

Interpretive Summary: Essential oils of some plants are considered promising environmentally-friendly insecticides that can be used as a component of integrated vector management (IVM). However, these oils tend to be insoluble in water and have low environmental stability compromising their use in vector control. A delivery system that protects essential oils from environmental degradation and enhances their solubility in water could facilitate their commercial development as biopesticides for pest and vector management. This study investigated the use of a starch derivative and garlic or asafoetida essential oils for controlling mosquito larvae. The results show that a mixture of starch and either garlic or asafoetida essential oil dispersed well in water and was more toxic to mosquito larvae compared to garlic or asafoetida essential oil alone. These findings demonstrate that a mixture of starch and some essential oils hold promise as an environmentally-friendly strategy for controlling mosquitoes.

Technical Abstract: Although the insecticidal properties of some plant essential oils are well-documented, their use in integrated pest and vector management is complicated by their high volatility, low thermal stability, high sensitivity to oxidation and low solubility in water. We investigated the use of bio-based N-1-hexadecylammonium chloride and sodium palmitate amylose inclusion complexes as emulsifiers for two essential oils, garlic and asafoetida, known to be highly toxic to mosquito larvae. Four emulsions of each essential oil based on amylose hexadecylammonium chloride and amylose sodium palmitate inclusion complexes were evaluated for their toxicity against Aedes aegypti L. larvae relative to bulk essential oils. All emulsions were significantly more toxic than the bulk essential oil with the lethal dosage ratios ranging from 1.09-1.30 relative to bulk essential oil. Droplet numbers ranged from 1.11 x 109 to 9.55 x 109 per mL and did not change significantly after a 6-month storage period. These findings demonstrate that amylose inclusion complexes enhance the toxicity of essential oils and could be used to develop novel bio-based essential oil formulations for controlling larvae of mosquito vectors of medical, veterinary, and economic significance.