Institute of Fundamental Technological Research

We report on biosynthesis of silver nanoparticles using aqueous leaf extract of Euphorbia sanguinea and its photocatalytic degradation of Congo red dye and melanogenesis inhibition activity of mushroom tyrosine enzyme. Surface Plasmon resonance bands obtained from UV-Vis spectra were within the range 430–436 nm. FT-IR studies reveal the presence of functional groups of the plant metabolites used as stabilizing agents of nanoparticles. The shape of silver nanoparticles is spherical with size ranges about 20–28.8 nm as confirmed by SEM. XRD patterns displayed well-defined crystalline peaks corresponding to the face-centred cubic structures of metallic silver nanoparticles. The results of photocatalysis showed high photocatalytic efficiency of 86% and 90% within 5 min and 60 min, respectively at a rate of solar radiation of in the degradation of Congo red dye. The AgNPs gave dose dependent melanogenesis inhibition activity with IC50 of 71.96 µg/ml, showing non competitive mode of inhibition

In the study, metabolites of Euphorbia sanguinea were used as benign reducing and stabilizing agents to obtain zinc oxide
nanoparticles (ZnO-NPs). The nanoparticles were evaluated as dual agent for photodegradation of Malachite green dye and
tyrosinase inhibitior of mushroom tyrosine enzyme. Surface plasmon bands and energy band gaps of the ZnO-NPs were
within the range 356–378 nm and 2.72–4.37 eV respectively as obtained from the UV–Vis spectra. SEM/EDS elemental
mapping of the nanoparticles gave flower-like shape and even distribution of zinc and oxygen. XRD result revealed crystallographic
peaks assigned to hexagonal phase of zinc oxide. The metal oxide nanoparticles were used to achieve 53% percentage
degradation of Malachite green dye solution in less than a minute of solar radiation, which increased to 92% in 60 min.
A first order kinetics with correlation coefficient R2
of 0.937, rate constant of 0.0084 min−1 and half-life of 82.52 min was
established for the photodegradation process. The ZnONPs exhibited good tyrosinase inhibition with IC50 of 49.016 μg/ml.
The mode of enzymatic inhibition was competitive with an inhibition constant (Ki) of 0.525 mM using Lineweaver–Burk
kinetic model.