Indigofera tinctoria leaf extract mediated green synthesis of silver and gold nanoparticles and assessment of their anticancer, antimicrobial, antioxidant and catalytic properties.

This study reports the synthesis of noble metal nanoparticles, namely silver and gold from their respective salt by leaf extract of a medicinal plant Indigofera tinctoria. This leaf extract plays a dual role as stabilizing and reducing agent for the formation of nanoparticles. The synthesized silver and gold nanoparticles were characterized by UV-vis. spectroscopy, FTIR spectroscopy, XRD, TEM, EDX and AFM analysis. All these techniques confirm the formation of crystalline nanoparticles. The cytotoxic effect of I. tinctoria leaf extract and the nanoparticles were studied on lung cancer cell line A549. It was shown that the cell viability decreases with increasing concentration and nanoparticles has more toxic effect on cancer cell than the pure leaf extract. IC50 value of I. tinctoria leaf extract, AuNP and AgNP respectively, are 71.92 ± 0.76 μg/ml, 59.33 ± 0.57 μg/ml and 56.62 ± 0.86 μg/ml. Antimicrobial activities were tested against both bacterial and fungal strains by agar well diffusion method. The synthesized nanoparticles show high antimicrobial activities towards all tested microbial strains with varying degree. The antioxidant activities of synthesized nanoparticles were analysed by using DPPH method and found that nanoparticles show higher antioxidant activities than the leaf extract. Outstanding catalytic activities of nanoparticles were demonstrated by employing the reduction reactions of o/p-niroanilines by NaBH4.