This report describes the synthesis of metallic silver nanoparticles (AgNPs) using extracts of four medicinal plants (Aegle marmelos (A. marmelos), Alstonia scholaris (A. scholaris), Andrographis paniculata (A. paniculata) and Centella asiatica (C. asiatica)). The bio-conjugates were characterized by UV-visible spectroscopy, scanning electron microscopyenergy dispersive spectroscopy (SEM-EDS), Fourier transform infrared spectrometry (FTIR), x-ray diffraction (XRD) and zeta potential. This analysis confirmed that UV-Vis spectral peaks at 375 nm, 380 nm, 420 nm and 380 nm are corresponding to A. marmelos, A. scholaris, A. paniculata and C. asiatica mediated AgNPs, respectively. SEM images revealed that all the obtained four AgNPs are predominantly spherical, fibres and rectangle in shape with an average size of 36-97 nm. SEM-EDS and XRD analysis confirmed the presence of elemental AgNPs in crystalline form for all the four nanoparticle samples. The phytochemicals of various medicinal plant extracts with different functional groups were responsible for reduction of Ag + to AgNPs, which act as capping and stabilizing agent. Among four types of AgNPs tested for anticancer activity, the Ap mediated AgNPs had shown enhanced activity against HepG2 cells (27.01 µg ml −1 ) and PC3 cells (32.15 µg ml −1 ).

A rapid and novel microwave-mediated protocol was established for extracellular synthesis of metallic silver (Ag) and zinc oxide (ZnO) nanoparticles using the extracts of macro-algae Gracilaria edulis (GE) and also examined its anticancer activity against human prostate cancer cell lines (PC3). The formation of silver nanoparticles (GEAgNPs) and zinc oxide nanoparticles (GEZnONPs) in the reaction mixture was determined by ultraviolet-visible spectroscopy. The synthesized Ag and ZnO nanoparticles were characterized by X-ray diffraction, Fourier transform infra-red spectroscopy, energy dispersive X-ray, and field emission scanning electron microscopy. The silver and zinc oxide nanoparticles were spherical and rod-shaped, respectively. Cell viability assays were carried out to determine the cytotoxic effects of AgNPs and ZnONPs against PC3 and normal African monkey kidney (VERO) cell line. The inhibitory concentration values were found to be 39.60, 28.55, 53.99 μg/mL and 68.49, 88.05, 71.98 μg/mL against PC3 cells and Vero cells for AgNPs, ZnONPs, and aqueous G. edulis extracts, respectively, at 48 h incubation period. As evidenced by acridine orange/ethidium bromide staining, the percentage of the apoptotic bodies was found to be 62 and 70 % for AgNPs and ZnONPs, respectively. The present results strongly suggest that the synthesized ZnONPs showed an effective anticancer activity against PC3 cell lines than AgNPs.

Green nanoparticle synthesis was achieved using environmentally acceptable plant extracts reducing and capping agents. The present study was based on assessments to the anticancer activities to determine the effect of synthesized silver nanoparticles (AgNPs) from three medicinal plants on human liver (HepG2) and prostate (PC3) cancer cell lines. The synthesis of AgNPs using Plumbago zeylanica (Pz), Semecarpus anacardium (Sa) and Terminalia arjuna (Ta) plant extracts in the reaction mixture was monitored by UV-visible spectroscopy. FTIR results clearly illustrated that the plant extracts containing prominent peaks of functional groups and biomolecules viz., tannins, phenols, flavonoids and triterpenoids those act as capping agents and involved in the stabilization of the synthesised silver nanoparticles. Synthesized AgNPs were spherical and cuboid in shape which is determined by SEM. Average size of the AgNPs were between 80-98, 60-95 and 34-70 nm for PzAgNPs, SaAgNPs and TaAgNPs, respectively. Further, the synthesized AgNPs were characterized by XRD, EDX, DLS and Zeta potential analysis. Moreover, the synthesized AgNPs exhibited a dose-dependent cytotoxicity against human liver and prostate cancer cell lines. The inhibitory concentration (IC50) values of HepG2, PC3 and Vero cells were found to be 70.97, 58.61, 96.41; 10.04, 42.77, 83.86; and 28.42, 41.78, 69.48 μg/ml for PzAgNPs, SaAgNPs and TaAgNPs at 48 h incubation. An induction of apoptosis was confirmed by DNA fragmentation, Hoechst, Rhodamine and AO/EtBr staining. The present results strongly suggested that the AgNPs synthesized using P. zeylanica, S. anacardium and T. arjuna extracts showed potential anticancer activity of HepG2 and PC3 cell lines.

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