Alcoholic extracts from Paulownia tomentosa leaves for silver nanoparticles synthesis

Abstract

Paulownia tomentosa (P. tomentosa) is a hardwood tree that has economic and scientific relevance but has no use as food. For that reason, we selected it to conduct a study on the synthesis of silver nanoparticles (AgNPs) using hydroalcoholic extracts from its leaves. Phytochemical sources had been widely used as reducing agents for synthesis of nanoparticles. Our work is the first approach for studying the correlation between the composition of the extracts and the AgNPs synthesis features. Isopropyl alcohol, ethanol, and water were proposed as extraction solvents. Nanoparticles were characterized by UV–vis, FTIR, and Scanning Electron Microscopy/Energy Dispersive X-ray spectroscopy (SEM/EDX) and the Antimicrobial activity was evaluated. Our findings suggest that the composition of the extracts varies with the selection of the extraction solvent. This is relevant because solvents with similar characteristics and polarity (isopropyl alcohol and ethanol) produced different AgNPs features such as ζ potential that was −20.5 ± 0.41, −25 ± 0.12 and 31 ± 0.79 mV for samples extracted with isopropyl alcohol, ethanol, and water, respectively. Samples obtained with isopropyl alcohol produced nanoparticles with the highest antioxidant activity and stability. Also, we found that size, shape, reaction kinetics, and bactericidal properties have a strong correlation with the composition of the plant extract. Our results justify the use of a wide range of extraction solvents to obtain detail implications on size and shape of nanoparticles, and the use of chromatographic techniques to determine each fraction composition. Our investigation is the first step in a coherent path to propose reaction mechanisms on nanoparticles synthesis using complex mixtures from Paulownia tomentosa extracts. Keywords: Biosynthesis, Silver nanoparticles (AgNPs), Paulownia tomentosa, Electrochemical-CUPRAC, Trolox Equivalent Antioxidant Capacity, Flavonoid oxidation