In vitro antibacterial, antioxidant and toxicity profile of silver nanoparticles green-synthesized and characterized from aqueous extract of a spice blend formulation

Here we report the synthesis, characterization and biological properties of silver nanoparticles (AgNPs) using the extract from a spice blend. AgNPs were prepared using 0.1 mmol/L AgNO₃ solution and aqueous extract from a spice blend of garlic, ginger and cayenne pepper. The nanoparticles were characterized using ultraviolet–visible (UV-vis) spectroscopy, scanning and transmission electron microscopy (SEM and TEM), energy dispersive X-ray (EDX), X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FTIR). The AgNPs formed within an hour of the reaction with colour change from yellow to dark brown and maximum absorbance at 420 nm in the UV-vis spectrum. SEM revealed well dispersed particles with little agglomeration, and the presence of elemental silver was confirmed by EDX. TEM confirmed the formation of poly-dispersed, spherical-shaped NPs with size range of 6–28 nm. FTIR showed that amine, protein, phenolic, aromatic and alkyne groups contributed to AgNPs synthesis, and XRD confirmed their crystalline and face-centred cubic nature. Both Gram-negative and Gram-positive bacteria were susceptible to the spice blend AgNPs with MIC of 0.0625 at 62.5 µg/mL. The AgNPs exhibited greater inhibition on DPPH radical with IC₅₀ < 31.25 µg/mL, while it was 68.75 µg/mL for ABTS. The nanoparticles were not toxic against MDA-MB-231 breast cancer cell lines. These spice blend nanoparticles would support the production of AgNPs with significantly enhanced pharmacokinetic properties and greatly improved therapeutic performance.