Biologically Synthesized Silver Nanoparticles by Aqueous Extract of Satureja intermedia C.A. Mey and Evaluation of Antioxidant Activity

Developing high-yield, low cost, nontoxic and environmentally friendly methods for metallic nanoparticles is an increasing need. Using plants towards synthesis of nanoparticles are emerging and beneficial with the presence of broad variability of bio-molecules in plants which can act as capping/stabilizing and reducing agents. Among the metallic nanoparticles, Silver has been enormously utilized for its diverse applications in the fields of bio labeling, opto-biosensors, cancer cell imaging, drug delivery systems, polarizing filters, electrical batteries, staining pigments, etc. [1]. In the present attempt, we evaluated total phenolic and flavonoid contents in aqueous extract of Saturaja intermedia C. A. Mey (Labiateae) collected from Gardaneh Almas (2350-2400 m), between Astara and Ardabil, on June 2014. Results showed that the extract is rich in flavonoids (21.123± 0.0698 μg/mL) and phenolic compounds (25.289±0.0698 μg/mL) and the plant could be a good choice for bio reduction process. So we investigated biosynthesis of SNPs by the aqueous extract of S. intermedia and found an easy and rapid procedure. For this reason, a 100 mL aliquot of a 0.01 M solution of AgNO3 was gradually added to 20 μL of theaqueous extract of S. intermedia. The mixture was kept in an ultrasonic during the addition and then was stirred in a magnetic stirrer (500 rpm) at room temperature for 48 hours. Silver nanoparticles were gradually obtained during the reaction and were washed by de-ionized water and dried for an hour in an oven at 100°C. Then the synthesized nanoparticles were characterized. UV-Vis spectrum of colloidal solution of SNPs showed a strong surface Plasmon resonance centered at 475 nm confirmed the nanocrystalline character of the particles [2]. The XRD study showed crystalline nature and face cubic center shape for nanoparticles. TEM study showed that the mean diameter and standard deviation for the silver nanoparticles were 29.29±28.18 nm. Electron donation ability of the extract and the colloidal solution of SNPs and also BHT as a standard antioxidant, were measured from the bleaching of the purple-colored methanol solution of DPPH [3]. Results showed that the aqueous extract of S. intermedia exhibited higher scavenging activity in concentrations 2 and 0.2 (μg/mL) compared to Ag/S. intermedia suspension and DPPH (as a standard). By reducing the concentration to 0.02 μg/mL and lower, BHT was more effective than the aqueous extract and Ag/S. intermedia suspenssion. It can be concluded that the aerial parts of S. intermedia is a good source of flavonids and phenolic compounds, a potent antioxidant and also a valuable choice for bio-reduction and biosynthesis of silver nanoparticles.