Green synthesis of antibacterial cerium oxide nanoparticles using Magnolia kobus leaves extract

Abstract

The aim of this work was to synthesize cerium oxide nanoparticles (CeO2-NPs) using the Magnolia kobus leaves extract, to determine the composition of the extract and the participation of its components in the synthesis of NPs, to study the morphology and structure of the obtained NPs, to investigate their antibacterial activity. The composition of the plant extract and involving of its components in green synthesis of CeO2-NPs was studied by high-performance liquid chromatography (HPLC) and matrix-assisted laser/desorption ionization mass spectrometry (MALDI MS). It has been shown that the extract contained phenolic compounds (derivatives of simple phenols, flavonols, hydroxybenzoic and hydroxycinnamic acids, lignans, coumarins), as well as carotenoids, chlorophylls, terpenoids and sterols. The composition of the liquid phase from the reaction mixture (reaction liquid) after the NPs formation was studied to determine the components of the extract involved in the synthesis of CeO2-NPs. According to the results of HPLC and MALDI MS studies, significant differences were found in the composition of the plant extract and the reaction liquid: hydroxybenzoic acids, flavonoids and terpenoids disappeared or their concentration was significantly decreased, the content of lignans changed to a lesser extent, and it was observed the appearance of hydrophilic low-molecular compounds probably formed as a result of synthesis and stabilization of NPs. Synthesized CeO2-NPs were characterized by means of scanning electron microscopy (SEM) and X-ray diffraction (XRD). According to SEM and XRD, CeO2-NPs had a crystalline structure and were of spherical shape; the average size of the crystallites was ~ 20 nm, and the diameter of the primary particles was 50 ± 10 nm. It has been found that hydroxybenzoic acids, flavonoids and terpenoids are active participants in the green synthesis of CeO2-NPs in the presence of Magnolia kobus leaves extract, while lignans (fargesin/kobusin and eudesmin) are involved in less extend in the reduction/stabilization of CeO2-NPs. The synthesized particles possess antibacterial properties and can be used in the preparation of materials for medical and biological purposes.