Antioxidant activity, metal-chelation, and photoirradiation mediated enhanced green synthesis of silver nanoparticles by the aqueous extract of the bark of Xylocarpus granatum

Xylocarpus granatum (XG) is a mangrove tree with potential therapeutic applications. The current study intends to demonstrate the photoirradiation-mediated green synthesis of silver nanoparticles, utilizing antioxidant and metal-chelating potential of the metabolites present in the aqueous extract of the bark of XG. The extract was produced by aqueous maceration of the bark for 24 h in dark conditions at room temperature. The GCMS analysis identified various proportions of primary and secondary metabolites. The total phenolic and flavonoid content of the extract was estimated to be 3.059 mmol and 2.119 mmol of gallic acid equivalents per gram of extract, respectively. Furthermore, 500 μg ml⁻¹ and 100 µg ml⁻¹ of extract demonstrated antioxidant activity and FRAP equivalent of 498.56 ± 0.156 µM of ascorbic acid and 195.93 ± 0.0035 µM of ascorbic acid, respectively. Likewise, 500 μg ml⁻¹ of extract demonstrated approximately 35 % iron- and copper-chelating potential against 0.1 mM FeSO₄ and 0.4 mM CuSO₄, respectively. The extract demonstrated silver nanoparticles synthesis in the dark which was significantly enhanced by photoirradiation under 825 lumens white LED light. The mean diameter of these nanoparticles was observed to be 36 ± 11.45 nm, with a poly-dispersive index of 0.276, indicating a homogenous nano-colloidal solution. The nanoparticles were predominantly spherical with approximately 17.5 % silver atoms and 37 % carbon atoms, indicating embedding of silver atoms in the extract nanocomposite that may lead to potential therapeutic application of the nanocomposite. Thus, the current study infers the antioxidant and metal-chelating potential of the extract may contribute to its nanotherapeutic applications.