Repellent activity of trans‐anethole and tea tree oil against Aedes aegypti and their interaction with OBP1, a protein involved in olfaction

Abstract

AbstractMosquitoes act as vectors for the transmission of various infectious pathogens. The associated diseases are prevalent in tropical and subtropical regions of the world and can be prevented by effective vector control and management. Natural compounds have become a potential alternative to synthetic repellents that are unsafe and harmful to the environment. The repellent activity of trans‐anethole and tea tree [Melaleuca alternifolia (Maiden & E. Betche) Cheel, Myrtaceae] oils was tested against the vector Aedes aegypti (L.) (Diptera: Culicidae) by performing a modified arm‐in‐cage and cloth‐patch repellent assay. Tea tree oil [EC50 = 0.002 mg ml−1, 95% confidence interval (CI) = 0.001–0.003] was found to be a more potent repellent than trans‐anethole (EC50 = 0.003 mg ml−1, 95% CI = 0.001–0.007). Tea tree oil was determined to have a complete protection time of 60 min, which was less than N,N‐dimethyl‐3‐methylbenzamide (DEET), which was used as a control (480 min). The binding affinity of trans‐anethole and terpinen‐4‐ol (a major component of tea tree oil) for the protein target AaegOBP1, a component of the olfactory system of Ae. aegypti, was determined using blind and targeted molecular docking. The results of molecular docking were in accordance with the findings of the repellent assay. OBP1 was found to have a better binding affinity for terpinen‐4‐ol (ΔG = −7.1 kcal per mol) than trans‐anethole (ΔG = −6.9 kcal per mol). In addition, a hydrogen bond of 0.1997 nm (1.997 Å) long was formed between PHE123 of OBP1 and terpinen‐4‐ol as established with Mcule. Further detailed analysis and experimentation of natural products as repellents is required as they may replace currently used synthetic repellents – natural repellents generally have less side effects and lower toxicity while being cost‐effective and easily available.