Ocimum tenuiflorum L mediated green synthesis of silver and selenium nanoparticles: antioxidant activity, cytotoxicity and density functional theory studies

Abstract

Inorganic nanoparticles (NPs) have found extensive application in medicine and pharmaceutics. Although chemical synthesis of NPs is the most commonly employed technique, it is often associated with toxicities due to the nature of the precursors and the experimental conditions used. Hence, there is a need for a safer biosynthetic approach. The current study involves the green synthesis of silver (Ag) and selenium (Se) NPs using an aqueous Ocimum tenuiflorum inflorescence extract. Total phenol and HPLC-MS based phytochemical analysis of the extract was performed. NPs were analysed using UV-visible, and Fourier transform infrared (FTIR) spectroscopy, electron microscopy (EM), x-ray diffraction (XRD) and nanoparticle tracking analysis (NTA). Surface plasmon resonance bands at 433 nm and 285 nm confirmed the synthesis of the Ag and SeNPs, respectively. NPs were monodisperse, small (<65 nm), with good stability and significant antioxidant activity. Cytotoxicity evaluated in the human embryonic kidney (HEK293), cervical carcinoma (HeLa) and breast adenocarcinoma (MCF-7) cells showed a dose-dependent trend with Se possessing better biocompatibility in the normal HEK293 cells than Ag. Density functional theory identified anthocyanins (delphinidin-5-O-beta-d-glucoside and delphinidin-3-O-glucoside) to have the most favourable NP-reducing and stabilising potential from the identified plant compounds.