Green synthesis of silver nanoparticles using aqueous extracts of three Sideritis species from Turkey and evaluations bioactivity potentials

Abstract The members of the genus Sideritis have a wide variety of phytochemicals and thus the genus are gaining interest to fabricate nanoparticles (via green synthesis) as sources reducing or stabilizer agents. In the present study, silver nanoparticles (AgNPs) were synthesized by an easy and eco-friendly method using aqueous extracts of three Sideritis species (Sideritis argyrea (SA), S. brevidens (SB), and S. lycia (SL)). These AgNPs were investigated in terms of cholinesterase (AChE: acetylcholinesterase and BChE: butyrylcholinesterase) and tyrosinase activities. The presence of (111), (200), (220) and (311) planes in Bragg's reflections verified the fcc (face-cantered-cubic) crystalline AgNPs. Sideritis species-directed AgNPs were characterized by surface plasmon resonance at 428–440 nm. Transmission electron microscopy (TEM) characterizations were showed the spherical and monodispersed of the AgNPs with an average particle size of 22–26 nm. Fourier transform infrared (FTIR) spectra were revealed functional groups responsible for the reduction of silver ions. Also, for the AgNPs were confirmed by the characterizations of Zeta Potential and Dynamic Light Scattering (DLS). Chlorogenic acid (CGA) was found as major component for all three species. We demonstrated that Sideritis-directed AgNPs showed excellent inhibitory activity against BChE, while Sideritis extracts have no effective inhibitory activity against AChE. Among AgNPs, SA AgNPs exhibited the greatest tyrosinase inhibitory activity with the value of 33.02 mg kojic acid equivalents (KAE)/g, following CGA AgNPs (18.31 mg KAE/g) and SB AgNPs (5.46 mg KAE/g). Regarding the extracts, they had similar tyrosinase inhibition activity (33.61–36.34 mg KAE/g). Our findings suggest that the green synthesis by using Sideritis extracts could be open a new horizon in the biotechnological applications such as bioactivity and drug delivery.