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.

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 was evaluated against to Xanthomonas phaseoli pv. phaseoli using the agar diffusion methods. The results showed that the evaluated extract was promising for the green synthesis of the SNP, which were visually identified by the formation of a dark brown complex and by 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 between others confirmed through phytochemical screening that evidenced the presence of flavonoids, phenols, leucoanthocyanidins, terpenes and steroids groups. Fluorescents SNP with high degree of agglomeration were visualized by microscopies technical used. A promissory antibacterial activity of SNP was demonstrated by a zone of inhibition of the microbial growing. These results suggest the need to go deeper in the physical-chemical characterization and kinetic studies and the biological evaluation to make possible the use of this vegetable source to future develop of antibacterial formulations to the bean seeds protection.

The essential oils are a powerful natural resource with antibacterial activity. This work aims at the mode of action of Lippia graveolens Kunth essential oil of plants growing in Cuba on Salmonella enterica subsp. enterica serovar Typhimurium. The effects of this oil on cell integrity were determined by time-kill, bacteriolysis and loss of 260 and 280-nm-absorbing material assays and total proteins leakage. Also, depolarization of the membrane by essential oil was monitored and intracellular and extracellular ATP was measured. The transmission electron microscopy (TEM) was used for observed morphologic change. Minimum inhibitory concentration (MIC) of L. graveolens essential oil and minimum bactericide concentration (MBC) were 0.4 and 0.8 mg/mL respectively. This essential oil showed a bactericidal action against over S . Typhimurium in a few minutes. After treatment, the cell lysis was not occurred, but little intracellular material and total proteins leakage were observed. This essential oil depolarizes the cell membrane, disturb metabolic processes and changes the structure of cytoplasmic membrane. These results suggest as primary mode of action of L. graveolens essential oil over S . Typhimurium an increased permeability of the membrane and depolarization of inside membrane, inhibition of ATPase or disturbance in proton motive force that finally provokes death of cells. L. graveolens essential oil is a botanic resource can be used for the control of the salmonellosis, foodborne disease.

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The resistance of microorganisms to conventional antimicrobials is one of the most serious health problems that affect not only the human, but also animals and plants, making the search for antimicrobial active ingredients a priority of global research. Green synthesis of antimicrobial silver nanoparticles (AgNPs) is a simple, cost-effective, rapid, reproducible, and environment friendly alternative for which numerous plant species have been reported for this purpose. Previous studies have shown the potential of Leea coccinea leaves in to the biosynthesis of antimicrobial silver nanoparticles. The current research aimed to study the kinetics of the reaction of synthesis of AgNPs by cationic bio-reduction from this botanical bioresource. A technology for the synthesis of AgNPs was established and the influence of operational parameters such as the bio-reduction conditions and the kinetics of the reaction were studied. AgNPs were characterized at different times by UV-VIS spectroscopic method, scanning electron microscopy, determination of particle size, and Z potential through Dynamic Light Scattering technique (DLS). Addition of tensoactive substances was evaluated for the stabilization of the suspension of nanoparticles. The results showed that spherical AgNPs smaller than 100 nm were obtained, which were visually identified by the formation of a dark brown complex with maximum absorption at 470 nm. Kinetic studies demonstrated the influence of the initial plant material on speed and performance, making evident a complex phenomenology with the possible occurrence of parallel reactions, which points to the possible reaction of different reducing compounds contained in this natural source. Addition of surface agents, such as SDS (0,5 %) or maltose (0,5 %), improved the stabilization in the aqueous medium, suggesting the continuation of studies to develop pharmaceuticals formulations based on AgNPs.