Abstract
The synthesis of silver nanoparticles (SNP) from plants is a simple, fast and environmentally safe route. In the present study, the aqueous extract of fresh leaves from Leea coccinea L. was evaluated as a possible source of reducing and stabilizing agents to obtain SNP. The synthesized SNP were characterized by spectroscopic techniques such as UV–visible spectrophotometry and Fourier transform infrared spectroscopy (FTIR), scanning electron and confocal microscopies and the antimicrobial activity against Xanthomonas phaseoli pv. phaseoli was evaluated using agar diffusion methods. The results showed that the evaluated extract was promising for the green synthesis of the SNP, which was visually identified by the formation of a dark-brown complex and the presence of a peak of maximum absorption at 470 nm in a UV–VIS spectrum. FTIR spectrum of SNP showed main characteristic signals of aromatic compounds, carboxylic group among others confirmed by phytochemical screening that made evident the presence of flavonoids, phenols, leucoanthocyanidins, terpenes and steroids groups. Fluorescent SNP with high degree of agglomeration were observed by the microscopical technics used. A promising antibacterial activity of SNP was shown by a zone of microbial growth inhibition. These results suggested the need for going deeper in the physico-chemical characterization and kinetic studies, as well as the biological evaluations to make possible the use of this plant source in the future development of antibacterial formulations for bean seed protection.
Highlights
Phytopathogenic bacteria cause a negative impact on agricultural production systems, decrease yields and increase economic losses (Pedroza et al 2013)
The use of chemical pesticides based on copper, either for the treatment of the seed or systemic treatment, is one of the most widespread alternatives to control this pest; numerous studies have shown the resistance of the bacteria (Ram et al 2018)
UV–visible spectroscopic absorbance (Fig. 3b) showed a signal with λmax around of 470 nm due to strong surface plasmon resonance, which reaffirms the formation of silver nanoparticles (SNP) (Travieso et al 2018)
Summary
Phytopathogenic bacteria cause a negative impact on agricultural production systems, decrease yields and increase economic losses (Pedroza et al 2013). Management of this pest is complex and multifactorial, in which the seed control is essential. In this sense, efforts are made for searching resistant varieties (Rodríguez et al 2015), biological and chemical del Carmen Travieso Novelles et al Bioresour. Numerous authors point out that the foliar application of copper-based bactericides, crop rotation, intercropping, among other actions, are successful if they are applied in an integrated management program (Ararsa et al 2018). The use of chemical pesticides based on copper, either for the treatment of the seed or systemic treatment, is one of the most widespread alternatives to control this pest; numerous studies have shown the resistance of the bacteria (Ram et al 2018)
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