Green synthesis of silver nanoparticles using Ilex paraguariensis extracts: antimicrobial activity and acetilcolinesterase modulation in rat brain tissue

The silver nanoparticles (AgNPs) green synthesis has been investigated by selecting naturally occurred reduction and stabilizing/capping agents. In this work, Ilex paraguariensis aqueous extract in the one-step biosynthesis of AgNPs is reported. The synthesis was carried out at room temperature under different pH (5.0, 6.8 and 8.5) and extract concentrations (2.5, 5.0 and 7.5% v v −1 ) resulting in average diameters ranging from 34 to 144 nm and polydispersity index (PDI) up to 0.51. The morphological characterization was performed by Transmission Electron Microscopy, associated with the UV-Vis Spectroscopy, showing that at higher pH the shape of AgNPs was more spherical rather than ellipsoidal. X-ray diffraction (XRD) pattern of AgNPs exhibited 2θ values corresponding to silver nanocrystals. Colloidal AgNPs solution synthesized with pH 8.5 and extract concentration of 2.5% v v −1 remained stable for 10 months of storage at ambient temperature. Fourier Transform Infrared Spectroscopy suggested that the polyphenols were responsible for the AgNPs formation. AgNPs presented bacteriostatic and bactericidal activity. AgNPs presented in vitro rat brain acetylcholinesterase (AChE) activity, with higher inhibition potential at 200 µL. So, it is concluded that AgNPs were synthesized with success, the pH and extract concentration influences in AgNPs size and morphology, consequently in its antimicrobial and AChE activity.