GREEN SYNTHESIS, CHARACTERIZATION, AND BIOEVALUATION OF SALVIA OFFICINALIS SILVER NANOPARTICLES FOR ALZHEIMER'S DISEASE THERAPY

Abstract

Alzheimer's disease (AD) is a progressive neurodegenerative disorder with limited therapeutic options, necessitating the development of safer and more effective alternative treatments. This study focused on the green biosynthesis, characterization, and in vitro biological evaluation of Salvia officinalis-derived silver nanoparticles (AgNPs) as a potential therapeutic approach for Alzheimer's disease. Aqueous leaf extract of S. officinalis served as both reducing and stabilizing agent for the synthesis of AgNPs from 1 mM silver nitrate solution. Successful nanoparticle formation was visually confirmed by color change to dark brown within 30-60 minutes. Comprehensive physicochemical characterization revealed spherical, uniformly dispersed nanoparticles with a mean hydrodynamic diameter of 20-22 nm and a polydispersity index (PDI) of 0.154, indicating excellent monodispersity. Scanning Electron Microscopy (SEM) confirmed smooth, spherical morphology with uniform surface coverage. Zeta potential analysis showed a narrow symmetrical distribution range of -20 mV to +20 mV, demonstrating colloidal stability. Fourier Transform Infrared (FTIR) spectroscopy identified key functional groups including O-H/N-H stretching (2500-3500 cm⁻¹), C=C aromatic ring stretching (1400-1600 cm⁻¹), and C-O stretching vibrations (1000-1200 cm⁻¹), confirming the involvement of phenolic compounds, flavonoids, and proteins in nanoparticle capping and stabilization. Biological evaluation demonstrated potent antioxidant activity with DPPH radical scavenging of 65.50 ± 4.20% and FRAP reducing power of 1550 ± 40.41 μM Fe²⁺ equivalents, exhibiting strong concentration-dependent activity (R² = 0.9572). The nanoparticles also displayed significant acetylcholinesterase (AChE) inhibitory activity in a dose-dependent manner, reaching 89.9 ± 1.2% inhibition at 650 μg/mL, comparable to the standard drug donepezil (98.9 ± 0.7%). These findings demonstrate that Salvia officinalis-derived AgNPs possess stable physicochemical properties, robust antioxidant capacity, and potent AChE inhibitory activity, establishing their potential as a promising nanotherapeutic platform for Alzheimer's disease management. Further in vivo studies and clinical optimization are warranted to validate their therapeutic efficacy.