Evaluation of antioxidant potential and reduction capacity of some plant extracts in silver nanoparticles' synthesis

The green synthesis of metallic nanoparticles is an active research area in nanotechnology. In the present study, antioxidant potential, total reducing capacity and silver nanoparticles' (Ag NPs) synthetic potential of methanolic leaf extracts of seven plant species were evaluated and compared. Antioxidant capacity, expressed as µmol Trolox equivalents g^-1 DW (µmol TE g^-1 DW), ranged from 116.0 to 1.80. The plants Rosmarinus sp. and Zataria Multiflora showed highest antioxidant capacities with IC₅₀ of 1.07 and 1.22 mg ml^-1, respectively. Total reducing capacity ranged from 7.6 to 0.17 mg gallic acid equivalent to g^-1 DW (mg GAE g^-1 DW). Plants with high antioxidant potentials also showed higher total reducing capacity. In fact, the order of the plants' reducing capacity was similar to that of their antioxidant potential. The same two plant species, i.e., Zataria Multiflora and Rosmarinus sp, with high reducing capacities, showed higher potentials for Ag NPs synthesis. It is concluded that reducing substances in the extracts contribute significantly to the antioxidant potential of the tested plant species, and plants with a high reducing capacity are excellent sources for the green synthesis of metallic nanoparticles. In addition, synthetic antioxidants have adverse effects on human health; therefore, to benefit more from the health promoting properties of plant species, evaluating their novel natural antioxidants is recommended.