Zinc oxide nanoparticles (ZnONPs) from Manilkara hexandra leaves: biogenic synthesis, GC–MS analysis and antibacterial activity

The present study aims to evaluate the cost-effective and eco-friendly synthesis of zinc oxide nanoparticles (ZnONPs), antibacterial activity, and gas chromatography-mass spectrometry (GC–MS) assay of an aqueous extract of Manilkara hexandra leaves (MHL). The sol–gel method was utilised to synthesise ZnONPs of MHL through centrifugation at 10000 rpm for five minutes. The synthesised ZnONPs were characterised by UV–visible spectroscopy, Fourier transform infrared spectrophotometer (FT-IR), Scanning electron microscopy (SEM), Transmission electron spectroscopy (TEM), and X-ray diffraction (XRD) techniques. The band-gap energy (Eg) measured is in the 3.29 eV range. The EDX spectrum showed that the ZnONPs of MHL contain an elemental silver signal, while the SEM and TEM spectra revealed that they are spherical in shape and have a rough surface. In addition, the bioactive chemicals responsible for synthesising ZnONPs in MHL were analysed using the gas chromatography-mass spectrometry (GC–MS) method. It was found that 5-hydroxymethylfurfural, butanedioic acid, and hexadecanoic acid are essential components of the aqueous extract of MHL. In addition, the synthesised ZnONPs of MHL showed antibacterial activity against Bacillus subtilis (B. subtilis) and Salmonella enterica (S. enterica), with significant ZOIs of 9.0 mm and 7.0 mm, respectively. Thus, our results suggest that the ZnONPs prepared from MHL could be helpful as an alternative to antibiotics in the treatment of B. subtilis and S. enterica infections.