Green synthesis of silver nanoparticles using Tridax procumbens: their characterization, antioxidant and antibacterial activity against MDR and reference bacterial strains

Silver nanoparticles (AgNPs) were synthesized by reducing 2 mM solution of AgNO3 using leaf extract of Tridax procumbens. Synthesized AgNPs were characterized by UV spectroscopy, FTIR-ATR, SEM, and TEM analyses. Antibacterial activity of AgNPs was evaluated against reference and MDR bacterial strains. Phytochemical estimation and antioxidant activity were carried out for aqueous extract of T. procumbens leaves as well as for AgNPs. The nanoparticles were reported oval to spherical in shape with an average size of 54.34 nm. The synthesized AgNPs showed considerable antibacterial activity against bacterial strains. The zone of inhibition ranged between 11.00 +/- 1.00 and 15.33 +/- 0.58 mm. Among reference bacterial strains, E. coli (15.33 +/- 0.58 mm) and S. aureus (15.33 +/- 0.58 mm) were found to be the most susceptible with MIC range in between 11.43 and 102.8 mu g/ml. Among the MDR strains, P. aeruginosa and E. coli showed inhibition zone of 14.33 +/- 0.58 mm with MIC of 102.8 mu g/ml. Cell leakage analysis showed an increase in protein leakage level and degradation of nucleic acid after treatment with AgNPs. Synthesized AgNPs showed higher amounts of total phenolic and flavonoids contents as compared to aqueous extract of Tridax procumbens leaves. The antioxidant activity of synthesized AgNPs and aqueous extract of Tridax procumbens leaves was determined using DPPH free radical scavenging, metal chelating, and beta-carotene linoleic assays and nanoparticles represented the higher free radical scavenging activity in all the assays. The present study concluded that Tridax procumbens can be used as a source for green synthesis of AgNPs which possesses potent antibacterial and antioxidant activities.