Catalytic and biological activities of green silver nanoparticles synthesized from Plumeria alba (frangipani) flower extract

Herein, we report the green synthesis of silver nanoparticles using Plumeria alba (frangipani) flower extract (FEE) and their biological applications. The formation of frangipani silver nanoparticles (FSNPs) was confirmed by UV-visible spectroscopy and characterized by DLS particle size analyzer, SEM/EDAX, FTIR, TGA/DSC and XRD. The synthesized spherical FSNPs were found to be 36.19 nm in size as determined by DLS particle size analyzer. EDAX data and XRD pattern of FSNPs confirmed the presence andface-centered cubic (fcc) phase structure of silver. The bioactive groups C-C and C-N present in FEE were involved in the formation of FSNPs as identified by FTIR analysis. FSNPs exhibited powerful catalytic activity by reducing 4-nitrophenol to 4-aminophenol within 8 min and the other organic dyes namely methylene blue and ethidium bromide were moderately degraded. Biological activities of FSNPs are evaluated by means of antioxidant, antibacterial and cytotoxic effect. Antioxidant potential of FSNPs was assessed by various in vitro assays in which they exhibited moderate antioxidant activity. The antibacterial effect of FSNPs was tested in two different pathogenic bacterial strains and their bacteriostatic effect was confirmed by growth kinetic study in Escherichia coli. The cytotoxic effect of FSNPs in COLO 205 was analyzed by MTT assay and the IC50 concentration was found at 5.5 and 4 mu g/ml respectively after 24 and 48 h of incubation. Cytotoxic effect of FSNPs in COLD 205 cells was associated with the loss of membrane integrity and chromatin condensation which might have played a crucial role in the induction of apoptosis as evidenced in AO/EB staining. (C) 2015 Elsevier B.V. All rights reserved.