Trop Biomed. 2023 Jun 1;40(2):241-249. doi: 10.47665/tb.40.2.016.
The development of new alternatives strategies to synthetic insecticides aimed at reducing pest populations by developing pesticides based on plant extracts without negative effects in non target organisms and environment. The present study was undertaken in order to assess the insecticidal activity of the crude methanolic extract of the Algerian Asteraceae Cotula cinerea, against the larval and the pupal stage of Culex pipiens (Diptera: Culicidae). It is also to determine the chemical composition of the used extract, and to understand the mechanism of toxic action of the tested extract. Based on the preliminary tests, five concentrations of the crude methanolic extract of C. cinerea (0.62, 1.25, 2.50, 3.75, and 5 mg/mL) were tested for their insecticidal activity according to the protocol recommended by the World Health Organization. The chemical profile of the extract was also obtained by high performance liquid chromatography (HPLC). Histopathological effects and inhibition of acetylcholinesterase activity in treated mosquitoes with LC were examined to elucidate the mechanism of the toxic effect of the tested extract (48 h post treatment). Eight compounds have been identified by HPLC. That includes four flavonoids (rutin, quercetin, myrcetin and cathechin), three phenolic acids (benzoic acid, vanillic acid, p-coumaric acid) and one alkaloid (berberine). C. cinerea methanolic extract showed good larvicidal and pupicidal activities with LC and LC values of 1.10 and 4.37 mg/mL respectively against pupae, 24h post treatment and 1.26, 2.35 mg/mL respectively against the fourth instar larvae. Data of enzymatic assay performed on LC and LC pupae and larvae revealed prominent neurotoxic effects. C. cinerea extract reduced the activity of acetylcholinesterase (AChE) enzyme in a concentration dependent manner. Obtained inhibition percentages, 48 h after treatment, were 35.11 ± 7.44 and 51.83 ± 4.04% for pupal stage and 30.98 ± 2.97 % and 48.77 ± 4.72% for the fourth instar larvae for LC and LC values respectively. Treated larvae and pupae showed also histopathological damages in the pupal cuticle and larval midgut. The results of this study showed that C. cinerea crude methanolic extract could be considered as an eco-friendly alternative for mosquito control.
为了减少害虫种群，开发基于植物提取物的杀虫剂，而不影响非目标生物和环境，人们正在研究新的替代合成杀虫剂的策略。本研究旨在评估阿尔及利亚菊科植物 Cotula cinerea 的粗甲醇提取物对致倦库蚊幼虫和蛹期的杀虫活性。同时，确定所用提取物的化学成分，并了解测试提取物的毒性作用机制。基于初步测试，根据世界卫生组织推荐的方案，测试了五种浓度的 C. cinerea 粗甲醇提取物（0.62、1.25、2.50、3.75 和 5mg/mL）的杀虫活性。提取物的化学特征也通过高效液相色谱（HPLC）获得。为了阐明测试提取物的毒性作用机制，检查了用 LC 处理的蚊子的组织病理学效应和乙酰胆碱酯酶活性抑制（处理后 48 小时）。通过 HPLC 鉴定出八种化合物，包括四种类黄酮（芦丁、槲皮素、杨梅素和儿茶素）、三种酚酸（苯甲酸、香草酸、对香豆酸）和一种生物碱（小檗碱）。C. cinerea 甲醇提取物对蛹期的 LC 和 LC 值分别为 1.10 和 4.37mg/mL，对 4 龄幼虫的 LC 和 LC 值分别为 1.26 和 2.35mg/mL，具有良好的幼虫和蛹杀虫活性。对 LC 和 LC 蛹和幼虫进行的酶活性测定数据显示出明显的神经毒性作用。C. cinerea 提取物以浓度依赖的方式降低乙酰胆碱酯酶（AChE）酶的活性。处理后 48 小时，获得的抑制百分比分别为 35.11±7.44%和 51.83±4.04%，LC 和 LC 值分别为 30.98±2.97%和 48.77±4.72%。处理过的幼虫和蛹在蛹皮和幼虫中肠也表现出组织病理学损伤。本研究结果表明，C. cinerea 粗甲醇提取物可作为一种控制蚊虫的环保替代品。
