Sunlight-Assisted Fabrication of Silver Nanoparticles using Terminalia neotaliala Capuron Aqueous Bark Extract: Evaluation of In vitro Antioxidant and Anti-inflammatory Activities

Sunlight-assisted rapid fabrication of silver nanoparticles (AgNPs) using aqueous bark extract of Terminalia neotaliala Capuron (TnB-AgNPs) and evaluation of in vitro antioxidant and anti-inflammatory activities.  Aqueous bark extract of T. neotaliala was used as a reducing agent in AgNPs formation under direct sunlight. Techniques like UV-Vis Spectroscopy, FTIR, XRD, DLS, HR-TEM with SAED were employed for the characterization studies. Further, antioxidant activity was determined by DPPH radical scavenging assay and anti-inflammatory activity by BSA anti-denaturation assay. The TnB-AgNPs formation was observed as a colour change from light-yellow to dark-brown with a λmax value of 414nm. FTIR spectra revealed different functional groups such as -OH, -CH, -C=O, -NH, -C-N groups associated with the presence of polyphenolic compounds in the bark extract. XRD confirmed the Face Centered Cubic crystalline nature with an average crystallite size of 26 nm. Z-average particle size was found to be 57nm with a zeta potential value of -40.9mV indicating excellent stability. HR-TEM studies depict spherical shape with average particle size of 34.81nm and the lattice planar spacing of 0.24nm. The TnB-AgNPs and bark extract showed % scavenging of 70.66±0.27% and 80.78±0.39 % (100 µg/mL) for antioxidant activity and % inhibition of 79.49±1.22% and 67.92±1.00% (500µg/mL) for anti-inflammatory activity at their highest concentration.  The present study demonstrates a rapid approach in producing small, spherical, stable, crystalline AgNPs using T. neotaliala bark extract under the influence of direct sunlight. The synthesized TnB-AgNPs showed moderate antioxidant and excellent anti-inflammatory activity indicating its potentiality in biomedical applications.