Green Synthesis of Silver Nanoparticles from Salvia Aethiopis L. and their Antioxidant Activity

Abstract

Salvia aethiopis L. was heated in distilled water for 2 hours. After filtration, water extract was treated with silver nitrate for 2 hours at 60°C to yield the silver nanoparticles (Sa-AgNPs). The structure of silver nanoparticles was elucidated by spectroscopic methods such as Ultraviolet-visible (UV-Vis), Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), and Scanning electron microscope (SEM). The maximum absorption in UV-Vis spectrum was observed at 508 nm. XRD pattern at (2θ) 38.1°, 44.3°, 64.4°, and 77.4° degrees can be assigned to the (111), (200), (220) and (311) Bragg’s reflections of the face-centered cubic crystalline structure. The average size of Sa-AgNPs was found as 74.09 nm by SEM analysis. The characteristic hydroxyl vibration signal appeared at 3222 cm− 1. Antioxidant activity of extract and Sa-AgNPs were carried out using DPPH•, ABTS•+ FRAP assay. The Sa-AgNPs revealed the considerable ABTS•+ scavenging effect with the value of 4.93 (IC50, µg/mL) compared to BHT (IC50, µg/mL, 8.34). However, Sa-AgNPs displayed the lower DPPH• activity (IC50, µg/mL, 24.37) than that of the standard BHT (IC50, µg/mL, 9.67). The reducing power activity of Sa-AgNPs was found as 4.52 (µmol TE/mg extract) while the standard BHT value was 488 (µmol TE/mg extract).