Recent studies have shown that biomolecules such as protein, phenol and flavonoids present in the plant extract play an important role in the reduction of metals ions and capping of the
nanoparticles . Although the reduction of metal salts is environmentally benign, it is chemically a complex phenomenon involving an array of plant compounds such as vitamins, enzymes/proteins, organic acids such as citrates, amino acids and polysaccharides . The preliminary phytochemical screening of secondary metabolites has clearly revealed the presence of glucosides, flavonoids, phenolic compounds, alkaloids and carbohydrates in the leaves extract of A. indica (data not shown). We strongly believe that glucosides may be responsible for the bio-reduction of both silver and chloroaurate ions. However, biosynthetic products or reduced BYL719 cofactors may also play a key role in the reduction of respective salts to nanoparticles. In this present study, the cytotoxicity of silver and gold nanoparticles was increased with the increasing
concentration of nanoparticles. This statement is true particularly in the case of MCF-7, SGI-1776 another human breast cancer cell, which showed 100% cell death at 50 μg/ml concentrations of silver nanoparticles . On the contrary, the mushroom derived silver nanoparticles showed significant cytotoxicity against MDA-MB-231 cell lines at comparatively low concentration (6 μg/ml) . The results of the present study suggest that silver and gold nanoparticles reduced PIK3C2G the viability of MDA-MB-231 cells in a dose dependent manner. Based on these studies, it is here speculated that the cytotoxicity of nanoparticles is relied much on the nature of cell types and size of particles. Many researchers have also drawn similar conclusion  and . Apoptosis is broadly considered as a distinctive mode of programmed cell death that eliminates genetically determined cells . The induction of apoptosis is confirmed by two factors, (1) reduced and shrunken
cells and (2) DNA fragmentation . In this study, silver and gold nanoparticles treated cells showed apoptotic features such as condensed nuclei, membrane blebbing and apoptotic bodies at 48 h and these morphological changes were evident through AO/EB dual staining. Adding strengthen to the fact, silver and gold nanoparticles treated MDA-MB-231 cells showed clear fragmented DNA ladders, suggesting that cell death is due to apoptosis. In general, the fragmented DNA ladders indicate late apoptotic process in which caspase-3 plays a pivotal role  and . The earlier studies have demonstrated that caspase-3 cascade activation is responsible for several apoptotic mechanisms . Thus, it is obvious that DNA fragmentation and caspase-3 activation mediate the apoptotic process.