Green Synthesis of Silver Nanoparticles from Salvia aethiopis L. and Their Antioxidant Activity

Salvia species have been used extensively in medicinal and food industries for years due to their significant secondary metabolites contents such as flavonoids and phenolic compounds. Silver nanoparticles capped and stabilized by Salvia aethiopis compounds are expected to reveal considerable biological effects. In this study, Salvia aethiopis L. was heated in distilled water for 2 h. After filtration, water extract was treated with silver nitrate for 2 h at 60 degrees 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), Scanning electron microscope (SEM), and zeta potential analyses. The maximum absorption in UV-Vis spectrum was observed at 508 nm. XRD pattern (2 theta) at 38.1 degrees, 44.3 degrees, 64.4 degrees, and 77.4 degrees 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). The zeta potential of Sa-AgNPs was found as - 20.3 mV displaying the stability of Sa-AgNPs. Antioxidant activity of extract and Sa-AgNPs were carried out using DPPH, ABTS(+) FRAP assay. The Sa-AgNPs revealed a considerable ABTS.(+) scavenging effect with the value of 4.93 (IC50, mu g/mL) compared to BHT (IC50, mu g/mL, 8.34). However, Sa-AgNPs displayed a lower DPPH. activity (IC50, mu g/mL, 24.37) than that of the standard BHT (IC50, mu g/mL, 9.67). The reducing power activity of Sa-AgNPs was found as 4.52 (mu mol TE/mg extract) while the standard BHT value was 488 (mu mol TE/mg extract).