Division of Entomology, Department of Zoology, School of Life Sciences, Bharathiar University, Coimbatore, 641 046, Tamil Nadu, India.
Parasitol Res. 2013 Mar;112(3):981-90. doi: 10.1007/s00436-012-3220-3. Epub 2012 Dec 13.
Green nanoparticle synthesis has been achieved using environmentally acceptable plant extract and ecofriendly reducing and capping agents. The present study was carried out to establish the larvicidal activity of synthesized silver nanoparticles (AgNPs) using leaf extract of Nerium oleander (Apocynaceae) against the first to fourth instar larvae and pupae of malaria vector, Anopheles stephensi (Diptera: Culicidae). Nanoparticles are being used in many commercial applications. It was found that aqueous silver ions can be reduced by the aqueous extract of the plant parts to generate extremely stable silver nanoparticles in water. The results were recorded from UV-Vis spectrum, Fourier transform infrared (FTIR) spectroscopy, scanning electron microscopy (SEM), and energy-dispersive X-ray (EDX) spectroscopy analysis. The production of the AgNPs synthesized using leaf extract of N. oleander was evaluated through a UV-Vis spectrophotometer in a wavelength range of 200 to 700 nm. This revealed a peak at 440 nm in N. oleander leaf extracts, indicating the production of AgNPs. The FTIR spectra of AgNPs exhibited prominent peaks at 509.12 cm(-1) (C-H bend alkenes), 1,077.05 cm(-1) (C-O stretch alcohols), 1,600.63 cm(-1) (N-H bend amines), 2,736.49 and 2,479.04 cm(-1) (O-H stretch carboxylic acids), and 3,415.31 cm(-1) (N-H stretching due to amines group). An SEM micrograph showed 20-35-nm-size aggregates of spherical- and cubic-shaped nanoparticles. EDX showed the complete chemical composition of the synthesized nanoparticles of silver. Larvicidal activity of aqueous leaf extract of N. oleander and synthesized AgNPs was carried out against Anopheles stephensi, and the results showed that the highest larval mortality was found in the synthesized AgNPs against the first to fourth instar larvae and pupae of Anopheles stephensi with the following values: LC(50) of instar larvae 20.60, 24.90, 28.22, and 33.99 ppm; LC(90) of instar larvae 41.62, 50.33, 57.78, and 68.41 ppm; and LC(50) and LC(90) of pupae 39.55 and 79.10 ppm, respectively. The aqueous leaf extract exhibited larval toxicity against the first to fourth instar larvae and pupae of Anopheles stephensi with the following values: LC(50) of instar larvae 232.90, 273.71, 318.94, and 369.96 ppm; LC(90) of instar larvae 455.95, 563.10, 639.86, and 730.30 ppm; and LC(50) and LC(90) of pupae 426.01 and 805.13 ppm, respectively. The chi-square value was significant at p < 0.05 level. The possible larvicidal activity may be due to penetration of nanoparticles through a membrane. The results could suggest that the use of plant N. oleander to synthesize silver nanoparticles is a rapid, environmentally safer, and greener approach for mosquito control. This could lead us to a new possibility in vector-control strategy.
使用环保的植物提取物和环保的还原剂和封端剂已经实现了绿色纳米粒子的合成。本研究旨在利用夹竹桃（夹竹桃科）叶提取物建立银纳米粒子（AgNPs）的杀幼虫活性，针对疟疾病媒按蚊（双翅目：蚊科）的第一至第四龄幼虫和蛹。纳米粒子在许多商业应用中得到使用。研究发现，植物部分的水相银离子可以被植物提取物还原，在水中生成极其稳定的银纳米粒子。结果从紫外-可见光谱、傅里叶变换红外（FTIR）光谱、扫描电子显微镜（SEM）和能量色散 X 射线（EDX）光谱分析中得到记录。使用夹竹桃叶提取物合成的 AgNPs 的产生通过紫外-可见分光光度计在 200 至 700nm 的波长范围内进行评估。这表明在夹竹桃叶提取物中在 440nm 处有一个峰，表明 AgNPs 的产生。AgNPs 的 FTIR 光谱在 509.12cm（-1）（C-H 弯曲烯烃）、1,077.05cm（-1）（C-O 伸展醇）、1,600.63cm（-1）（N-H 弯曲胺）、2,736.49 和 2,479.04cm（-1）（O-H 伸展羧酸）和 3,415.31cm（-1）（由于胺基团的 N-H 拉伸）处显示出突出的峰。SEM 显微照片显示出 20-35nm 大小的球形和立方形状纳米粒子的聚集。EDX 显示了合成的银纳米粒子的完整化学成分。对按蚊的水提夹竹桃叶和合成的 AgNPs 的杀幼虫活性进行了测试，结果表明，在第一至第四龄幼虫和蛹的按蚊中，合成的 AgNPs 的幼虫死亡率最高，其值分别为：20.60、24.90、28.22 和 33.99ppm 的第一龄幼虫 LC（50）；41.62、50.33、57.78 和 68.41ppm 的第一龄幼虫 LC（90）；39.55 和 79.10ppm 的蛹 LC（50）和 LC（90）。水提夹竹桃叶对按蚊的第一至第四龄幼虫和蛹表现出杀幼虫毒性，其值分别为：232.90、273.71、318.94 和 369.96ppm 的第一龄幼虫 LC（50）；455.95、563.10、639.86 和 730.30ppm 的第一龄幼虫 LC（90）；426.01 和 805.13ppm 的蛹 LC（50）和 LC（90）。卡方值在 p < 0.05 水平上显著。可能的杀幼虫活性可能是由于纳米粒子通过膜渗透。结果表明，使用植物夹竹桃来合成银纳米粒子是一种快速、环境更安全、更环保的蚊虫控制方法。这可能为我们的蚊虫控制策略提供新的可能性。
