Synthesis and characterization of green tea (Camellia sinensis (L.) Kuntze) extract and its major components-based nanoflowers: a new strategy to enhance antimicrobial activity

Abstract

In this study, for the first time, a novel organic–inorganic nanobio-antimicrobial agent called “nanoflowers” (Nfs) from Camellia sinensis (L.) Kuntze extracts and its main components were produced and the increase in the antimicrobial activity of the Nfs was elucidated. While the green tea (GT) extract (obtained in ethanol and water) and its main components (caffeine, catechin) were involved as organic components in the formation of the Nfs, copper(II) ions (Cu²⁺) were the inorganic component. The structures of the Nfs were examined with several techniques such as Scanning Electron Microscopy (SEM), Fourier transform infrared spectrometry (FT-IR) and Energy-Dispersive X-ray (EDX) spectroscopy. The structural examination demonstrated that the presence of Cu–O and Cu–N bonds in Nfs can be an indication of the Nfs formation. Antimicrobial activities of the free GT extracts, caffeine (cf), catechin (ct) and their Nfs were systematically studied against Staphylococcus aureus (ATCC 25923), Escherichia coli (ATCC 25922) and Candida albicans (ATCC 90028) with broth microdilution and short time-kill assay. The peroxidase-mimicking activity depending on a Fenton-like reaction mechanism of the Nfs was measured against guaiacol in the presence of H₂O₂. In addition, total phenol contents of free GT extracts and their Nfs were calculated by Folin Ciocalteu method. Our results demonstrated that plant extract based Nfs technology is promising and may find potential applications in various scientific and technical fields.