Viral diseases transmitted by the female Aedes aegypti L. are considered a major public health problem. The aerial parts of Helicteres velutina K. Schum (Sterculiaceae) have demonstrated potential insecticidal and larvicidal activity against this vector. The objective of this research was to investigate the mechanisms of action involved in the larvicidal activity of this species. The cytotoxicity activity of H. velutina fractions and compounds of crude ethanolic extract of the aerial parts of this species was assessed by using fluorescence microscopy and propidium iodide staining. In addition, the production of nitric oxide (NO) and hemocyte recruitment were checked after different periods of exposure. The fluorescence microscopy revealed an increasing in larvae cell necrosis for the dichloromethane fraction, 7,4′-di-O-methyl-8-O-sulphate flavone and hexane fraction (15.4, 11.0, and 7.0%, respectively). The tiliroside did not show necrotic cells, which showed the same result as that seen in the negative control. The NO concentration in hemolymph after 24 h exposure was significantly greater for the dichloromethane fraction and the 7,4′-di-O-methyl-8-O-sulphate flavone (123.8 and 56.2 µM, respectively) when compared to the hexane fraction and tiliroside (10.8 and 8.3 µM, respectively). The presence of plasmocytes only in the dichloromethane fraction and 7,4′-di-O-methyl-8-O-sulphate flavone treatments suggest that these would be the hemocytes responsible for the highest NO production, acting as a defense agent. Our results showed that the larvicidal activity developed by H. velutina compounds is related to its hemocyte necrotizing activity and alteration in NO production.

中文翻译：

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Helicteres velutina K. Schum 地上部分的组分和化合物对埃及伊蚊的杀幼虫作用机制的见解

由雌性埃及伊蚊传播的病毒性疾病被认为是一个主要的公共卫生问题。Helicteres velutina K. Schum (Sterculiaceae) 的地上部分已证明对这种载体具有潜在的杀虫和杀幼虫活性。本研究的目的是研究该物种杀幼虫活性所涉及的作用机制。通过使用荧光显微术和碘化丙啶染色评估 H. velutina 级分和该物种地上部分的粗乙醇提取物的化合物的细胞毒性活性。此外，在不同的暴露时间后检查一氧化氮 (NO) 的产生和血细胞募集。荧光显微镜显示二氯甲烷部分的幼虫细胞坏死增加，7，4'-di-O-methyl-8-O-sulphate 黄酮和己烷馏分（分别为 15.4、11.0 和 7.0%）。tiliroside 没有显示坏死细胞，这显示出与阴性对照相同的结果。与己烷部分和 7,4'-二-O-甲基-8-O-硫酸盐黄酮（分别为 123.8 和 56.2 µM）相比，暴露 24 小时后血淋巴中的 NO 浓度显着更高。 tiliroside（分别为 10.8 和 8.3 µM）。仅在二氯甲烷部分和 7,4'-二-O-甲基-8-O-硫酸盐黄酮处理中存在浆细胞，这表明这些将是负责最高 NO 产生的血细胞，充当防御剂。我们的结果表明，由 H.