Green synthesis of silver nanoparticles using stem bark extract of Annona senegalensis : characterization and its antibacterial potency

The green synthesis of nanoparticles has been a vital aspect in the search for novel antimicrobial agents. This research aimed at biosynthesis, characterization and preliminary evaluation of the antibacterial properties of silver nanoparticles (AgNPs) from the back extract of Annona senegalensisis. The bark of Annona senegalensis was scraped from the stem, washed, air-dried, pulverised and extracted. Four millilitre (4 ​ml) of the extract was pipetted into 36 ​mL (36 ​ml) of silver nitrate solution (5 ​mM AgNO3) in a conical flask. The resulting solution was subjected to magnetic stirring at room temperature (28 ​°C ​± ​2) till AgNPs were formed. The synthesized AgNPs were filtered, washed with deionized water and dried in oven at 40 ​°C. Fourier transform infrared (FTIR) analysis was carried out on the synthesized AgNPs. The AgNPs synthesized was also characterized with UV–visible spectrophotometer (UV), scanning electron microscope (SEM), transmission electron microscopy (TEM), energy-dispersive X-ray (EDX) spectroscopy to ascertain the physico-chemical and morphological properties of the AgNPs. The antimicrobial investigation was carried out following standard method. The observation of colour change (pale yellow to dark brown) during the synthesis and maximum absorbance at wavelength 431.19 ​nm in the UV spectrum confirmed the formation of AgNPs. The FTIR analysis showed that the biomolecules responsible for the reduction of silver ion contain O–H functional groups. The electron microscopy studies indicated that the AgNPS are spherical in shape with nanoparticles sizes of 11–24.76 ​nm. EDX analysis showed that the AgNPs contain high amount of silver and few other elements. The antimicrobial study showed high zones of inhibition 22.75–33.75 against tested bacteria. The simplicity of the synthesis of AgNPs from the extract of the stem bark of Annona senegalensisis and relatively high zones of inhibitions shown by the AgNPs are strong evidences of the possible application of Annona senegalensisis in the synthesis of novel therapeutic agent against infections from bacteria and fungi.