Biogenic synthesis of silver nanoparticle from flower extract of Wedelia chinensis and their antibacterial and antioxidant activity

Wedelia chinensis is a medicinal herb of the family Asteraceae. Green synthesis of silver nanoparticles (AgNPs) was done by using flower extract of Wedelia chinensis. Optimum conditions for AgNPs synthesis were as such: flower extract and AgNO3 (0.1 M) were taken in 1:9 ratio; temperature- 30 °C; reaction time- 12 h. UV-Visible spectra of the synthesized nanoparticle showed maximum absorption at 400 nm. Crystalline nature of silver nanoparticle was confirmed by XRD pattern. Through TEM, average size of AgNPs was observed as 51.2 nm. FTIR indicated participation of various functional groups of flower extract in the formation of nanoparticles. In DLS study, AgNPs of size 121 nm showed 100% intensity. Zeta potential was recorded as −1.24 mV. Strong peak of silver was observed in EDX study. AgNPs alone showed effective inhibition against all pathogenic bacteria taken as test organisms, but its combination with the antibiotics showed considerable enhancement in antibacterial activity. Inhibition for methicillin resistant Staphylococcus aureus (MRSA) was maximum when nanoparticles were taken in the combination of antibiotics and the extract. Significant antioxidant potential of AgNPs were observed in DPPH, ascorbic acid and DNA nicking assays. Thus, AgNPs of Wedelia chinensis flower extract showed significant medicinal efficacy as antioxidant and antibacterial.