Pharmacology Division, Department of Pharmacy and Pharmacology, Faculty of Health Sciences, University of the Witwatersrand, Johannesburg, South Africa; WITS Research Institute for Malaria, Faculty of Health Sciences, University of the Witwatersrand, Johannesburg, South Africa.
WITS Research Institute for Malaria, Faculty of Health Sciences, University of the Witwatersrand, Johannesburg, South Africa; School of Pathology, Faculty of Health Sciences, University of the Witwatersrand, Johannesburg, South Africa; Centre for Emerging Zoonotic and Parasitic Diseases, National Institute for Communicable Diseases of the National Health Laboratory Service, Johannesburg, South Africa.
Exp Parasitol. 2023 Aug;251:108569. doi: 10.1016/j.exppara.2023.108569. Epub 2023 Jun 15.
Malaria is transmitted by infected female Anopheles mosquitoes, and An. arabiensis is a main malaria vector in arid African countries. Like other anophelines, its life cycle comprises of three aquatic stages; egg, larva, and pupa, followed by a free flying adult stage. Current vector control interventions using synthetic insecticides target these stages using adulticides or less commonly, larvicides. With escalating insecticide resistance against almost all conventional insecticides, identification of agents that simultaneously act at multiple stages of Anopheles life cycle presents a cost-effective opportunity. A further cost-effective approach would be the discovery of such insecticides from natural origin. Interestingly, essential oils present as potential sources of cost-effective and eco-friendly bioinsecticides. This study aimed to identify essential oil constituents (EOCs) with potential toxic effects against multiple stages of An. arabiensis life cycle. Five EOCs were assessed for inhibition of Anopheles egg hatching and ability to kill larvae, pupae and adult mosquitoes of An. arabiensis species. One of these EOCs, namely methyleugenol, exhibited potent Anopheles egg hatchability inhibition with an IC value of 0.51 ± 0.03 μM compared to propoxur (IC: 5.13 ± 0.62 μM). Structure-activity relationship study revealed that methyleugenol and propoxur share a 1,2-dimethoxybenze moiety that may be responsible for the observed egg-hatchability inhibition. On the other hand, all five EOCs exhibited potent larvicidal activity with LC values less than 5 μM, with four of them; cis-nerolidol, trans-nerolidol, (-)-α-bisabolol, and farnesol, also possessing potent pupicidal effects (LC < 5 μM). Finally, all EOCs showed only moderate lethality against adult mosquitoes. This study reports for the first time, methyleugenol, (-)-α-bisabolol and farnesol as potent bioinsecticides against early life stages of An. arabiensis. This synchronized activity against Anopheles aquatic stages shows a prospect to integrate EOCs into existing adulticide-based vector control interventions.
疟疾通过受感染的雌性按蚊传播，而阿蚊是干旱非洲国家的主要疟疾传播媒介。与其他按蚊一样，其生命周期包括三个水生阶段：卵、幼虫和蛹，然后是自由飞行的成虫阶段。目前使用合成杀虫剂的蚊虫控制干预措施针对这些阶段使用杀虫剂，或不太常见的幼虫杀虫剂。由于几乎所有常规杀虫剂的抗药性不断上升，因此寻找同时作用于按蚊生命周期多个阶段的药剂具有成本效益。更具成本效益的方法是从天然来源发现此类杀虫剂。有趣的是，精油是具有成本效益和环保的生物杀虫剂的潜在来源。本研究旨在确定具有潜在毒性作用的精油成分 (EOC)，以抑制阿蚊的生命周期的多个阶段。评估了五种精油成分 (EOC) 对按蚊卵孵化的抑制作用以及杀死阿蚊幼虫、蛹和成虫的能力。其中一种精油成分，即甲基丁香酚，对按蚊卵孵化具有很强的抑制作用，IC 值为 0.51 ± 0.03 μM，而相比之下，扑灭威的 IC 值为 5.13 ± 0.62 μM。构效关系研究表明，甲基丁香酚和扑灭威具有 1,2-二甲氧基苯部分，这可能是导致观察到的卵孵化抑制的原因。另一方面，所有五种精油成分都表现出很强的杀幼虫活性，LC 值小于 5 μM，其中四种成分；顺式-香叶醇、反式-香叶醇、(-)-α- 倍半萜醇和法呢醇，也具有很强的杀蛹活性 (LC<5 μM)。最后，所有精油成分对成蚊的致死率仅为中等。本研究首次报道甲基丁香酚、(-)-α-倍半萜醇和法呢醇是阿蚊早期生命阶段的有效生物杀虫剂。这种对按蚊水生阶段的同步作用显示了将 EOC 整合到现有的以杀虫剂为基础的蚊虫控制干预措施中的前景。
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