Silver nanoparticles mediated by Callistemon citrinus extracts and their antimalaria, antitrypanosoma and antibacterial efficacy

Abstract

In this report, three biosynthesized silver nanoparticles (AgNPs) obtained from the reduction of silver nitrate (AgNO3) by the aqueous crude extracts of aerial parts of Callistemon citrinus plant were characterized by means of ultraviolet–visible spectroscopy (UV–vis), X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive X-ray (EDX), transmission electron microscopy (TEM) and Fourier transformed infrared (FTIR).The XRD revealed that the AgNPs were crystalline in nature while the TEM showed that the shapes were spherical with an average size of 29 nm. The SEM and EDX demonstrated triangular shaped materials and that the AgNPs were made up of silver and oxygen only, absorption spectra confirm by UV–vis signifies the dispersed nature of the synthesized nanoparticles with absorption band observed at 280 nm for the leaf. FTIR had absorption bands at about 1700 cm−1 in all spectra's establishing the CO stretching owing to amide bond, another remarkable peak at 3400 cm−1 was seen in the crude extract which was ascribed to the OH stretching from water as a result of the aqueous nature of the plant extracts used. It is interesting to know that this peak was not seen in the AgNPs demonstrating the development of calcined AgNPs, in addition to this, peak at 420 cm−1 was observed for all the three nanoparticles synthesized and this shows the successfully synthesis of the AgNPs. The antimicrobial activities of the of the AgNPs was also confirm via both gram positive and gram negative bacteria strains with a very significant inhibitory action, MIC values of 7.8125 mg/mL were documented for all the silver nanoparticles. Potent antiplasmodial activities with IC50 ranging from 2.99–5.34 μg/mL were also recorded and a poor IC50 of 107.30 μg/mL for antitrypanosoma activity of the leaf AgNPs was also documented.