Betaine-Based Deep Eutectic Grape Pomace Extract Mediated Synthesis of Silver Nanoparticles with Antibacterial Activities

This paper presents a synthesis of silver nanoparticles by the novel method with grape pomace extract obtained by eco-friendly "green" solvent, namely, deep eutectic solvent (DES). The electrical conductivity of deep eutectic solvents was measured, and the width of electrochemical stability window was evaluated depending on water content in the solvent (0-25%). The DES was used to obtain the extract, and the latter was used in synthesis nanoparticles. The bands found in the FTIR spectrum were found to be associated with phenolic compounds. Grape pomace extract (GPE-DES) were analyzed by HPLC-DAD-MS to identify extracted compounds. The phytochemical profile of GPE-DES exhibits a high amount of the hydroxycinnamic acids (similar to 23%), followed by anthocyanins (similar to 19%). Furthermore, caffeic acid (164.5 mu g/g), gallic acid (792.4 mu g/g), and (+)-catechin (511.3 mu g/g) were quantified with HPLC. A sharp absorbance peak at 436 nm was found using a UV-visible spectrophotometer, confirming the presence of AgNPs. The extensive spectroscopic study enabled the identification of synthesized AgNPs. The silver nanoparticles with round shape were noticed on the scanning electron microscopy micrographs with the particle size in the range of 10-20 nm. High antibacterial potential has been proven against gram-positive spore-forming B. subtilis and gram-negative bacteria E. coli with 9 mm and 16 mm zone inhibition, respectively, observed by agar well diffusion method. Mitotic index (MI) and chromosomal aberrations (CAs) were assessed by Allium cepa assay. The synthesized silver nanoparticles do not induce cytogenotoxic and genotoxic changes in Allium cepa L. with nanoparticles at concentration up to 10%. The silver nanoparticles are biocompatible and non-toxic.