Green synthesis of Stereospermum suaveolens capped silver and gold nanoparticles and assessment of their innate antioxidant, antimicrobial and antiproliferative activities.

Plant-extract mediated nanoparticles synthesis is a viable alternative to chemical reduction techniques. Here, we report the microwave-assisted rapid synthesis of silver and gold nanoparticles by the phytoreducer Stereospermum suaveolens for the first time. The formation of the nascent silver and gold nanoparticles is confirmed by their intense surface plasmon resonance peaks at 431 and 585 nm in UV-visible spectroscopy. The poly phenolic and alcoholic functional groups present in the aqueous root bark extract that performed the bioreduction processes have been detected using Fourier transform infrared spectroscopy. Powder X-ray diffraction and selected area electron diffraction patterns settled face centered cubic crystal structures to both silver and gold nanoparticles with a preferred orientation towards the (111) plane. Transmission electron microscopic analysis proved more or less spherical geometry of the silver and gold nanoparticles with average diameter of 49.77 ± 11.64 and 27.19 ± 5.96 nm, respectively. The nanoparticles showed excellent free-radical scavenging activity than the root bark extract Stereospermum suaveolens and the IC50 values obtained were 108.36 ± 1.62, 45.59 ± 0.18, 34.53 ± 0.31 µg/mL, respectively, for the extract, gold and silver nanoparticles. The metal nanoparticles have accomplished good antimicrobial properties towards bacterial and fungal pathogens and were demonstrated herein. The antiproliferative effects of the synthesized silver and gold nanoparticles on human lung adenocarcinoma cells A549 were studied using the MTT assay and the obtained IC50 values 33.81 ± 0.72 and 52.97 ± 0.73 µg/mL lies in the clinical range.