In this study, Zonariacrenata J. Agardh was selected for the preparation of silver nanoparticles based on the presence of bioactive secondary metabolites. Freshly collected marine alga was used for the preparation of aqueous extract as the reducing and capping agent. Various concentration of extract (1%-5%) was added to silver nitrate solution. Brownish black color change was observed which indicates the formation of silver nanoparticles. Silver NPs was then isolated from the solution by evaporating and overnight drying on dryer. The synthesized silver NPs were subjected to FT-I R analysis and TEM analysis. FT-IR analysis revealed the role of functional groups in the formation of AgNPs. A shift from 1209 cm-1 to 1211 cm-1 was due to the involvement of the ether linkages of flavanone that are absorbed on the surface of metal NPs. A strong intense band at 1354 cm-1 was shifted to 1361 cm-1 which indicates the interactions of ester group. Shift from 1629 cm-1to 1631 cm-1reveals the participation of carbonyl group. TEM analysis of silver nanoparticles shows spherical and quasi- spherical shape in the dimensions ranging from 10nm to 40nm. Antioxidant properties were observed in green synthesized silver nanoparticles. A549 cell line treated with silver nanoparticles decreased cell viability. 35% cell death was determined at 50 µg/ml nanoparticles concentrations. The silver nanoparticles were incubated with MCF-7 at various concentrations, and the nanoparticles decreased MCF- 7 cell viability. At 6.25 µg/ml, 94.8% viability was observed and it decreased to 52.6% at 25 µg/ml concentration.
