The green biosynthesis of metal nanoparticles of already explored phytomedicines has many advantages such as enhanced biological action, increased bioavailability, etc. In this direction, keeping in view the peculiar medicinal value of Tropaeolum majus L., we synthesized its silver nanoparticles (AgNPs) by adopting eco-friendly and cost-effective protocol by using methanolic and aqueous extract of T. majus . The synthesized AgNPs were characterized by using several techniques including UV spectroscopic analysis, FTIR analysis, and atomic force microscopy. The methanolic/aqueous extracts of T. majus and synthesized AgNPs were assessed for antioxidant potential and antimicrobial effect. The preliminary screening showed that the T. majus extracts have variety of reducing phytochemicals including tannins, terpenoids, flavonoids, and cardiac glycosides. The green synthesis of AgNPs was confirmed by the appearance of sharp peak at 430–450 nm in the UV-Visible spectra. The FTIR spectral analysis of extract and AgNPs exhibited that peaks at 2947.23, 2831.50, 2592.33, 2522.89, and 1,411 cm −1 disappeared in the spectra of FTIR spectra of the AgNPs, indicating carboxyl and hydroxyl groups are mainly accountable for reduction and stabilization of AgNPs. Atomic force microscopic scan of the synthesized AgNPs confirmed its cylindrical shape with size of 25 µm. The extracts and AgNPs were investigated for antioxidant potential by DPPH-free radical essay, which showed that aqueous extract has significant and dose-independent antioxidant activity; however, the synthesized AgNPs showed decline in antioxidant activity. The extracts and synthesized AgNPs were also evaluated for antibacterial activity against Klebsiella pneumonia , Staphylococcus aureus , and Bacillus subtilis. Neither extract nor AgNPs were active against Klebsiella pneumonia. The aqueous and methanolic extract exhibited inhibition against Bacillus subtilis and their synthesized AgNPs were active against Staphylococcus aureus. Our data concluded that the extracts of T. majus have necessary capping and reducing agents which make it capable to develop stable AgNPs. The aqueous extract of T. majus has potential antioxidant effect; however, the AgNPs did not enhance its free radical scavenging effect. The bacterial strains’ susceptibility of the extract and AgNPs was changed from Bacillus subtilis to Staphylococcus aureus , respectively. The biological action of AgNPs is changed in case of antibacterial activity which means that AgNPs might change the specificity of T. majus and likewise other drugs.

中文翻译：

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用非洲对虾（Tropaeolum majus）绿色合成银纳米颗粒：植物化学筛选和抗菌研究

已开发的植物药的金属纳米颗粒的绿色生物合成具有许多优点，例如，具有增强的生物作用，增加的生物利用度等。在这个方向上，考虑到Tropaeolum majus L.的特殊药用价值，我们通过以下方法合成了其银纳米颗粒通过使用甲醇和水提取物来提取环保的，经济高效的方案。合成的AgNPs使用多种技术进行了表征，包括UV光谱分析，FTIR分析和原子力显微镜。评估了印度魔芋的甲醇/水提取物和合成的AgNPs的抗氧化潜力和抗菌作用。初步筛选显示，毛枣提取物具有多种还原性植物化学物质，包括丹宁酸，萜类，黄酮类和强心苷。AgNPs的绿色合成被紫外可见光谱中在430–450 nm处出现的尖峰所证实。提取物和AgNPs的FTIR光谱分析显示，AgNPs的FTIR光谱中的峰出现在2947.23、2831.50、2593.23、2522.89和1,411 cm -1处消失，这表明羧基和羟基是造成AgNPs还原和稳定的主要原因。合成AgNPs的原子力显微镜扫描证实了其圆柱形形状，尺寸为25 µm。通过DPPH自由基研究了提取物和AgNPs的抗氧化潜力，结果表明水提取物具有显着且不依赖剂量的抗氧化活性。然而，合成的AgNPs显示抗氧化剂活性下降。还评估了提取物和合成的AgNPs对肺炎克雷伯菌，金黄色葡萄球菌和枯草芽孢杆菌的抗菌活性。提取物和AgNP均未对肺炎克雷伯菌具有活性。含水和甲醇提取物表现出对枯草芽孢杆菌的抑制作用，其合成的AgNP对金黄色葡萄球菌具有活性。我们的数据得出的结论是，山茱T提取物具有必要的加帽和还原剂，使其能够形成稳定的AgNP。ma树的水提物具有潜在的抗氧化作用。然而，AgNPs没有增强其清除自由基的作用。提取物和AgNPs的细菌敏感性分别从枯草芽孢杆菌变为金黄色葡萄球菌。