The meticulous modulations of size and morphology are challenging to produce scale of plants mediated gold nanoparticles (AuNPs). In addition, the specific role of phytochemicals to precede the bio-reduction reaction and capping of the nanoparticles is also a mystery and need to be addressed. In the same line of action, we reported a green, eco-friendly, efficient and one-step method for synthesis of tailored size and shaped AuNPs and were controlled by various process parameters including pH, volume of extract and concentration of gold precursor. Bio-reduction process and formation of AuNPs were identified through various characterization techniques including UV-vis, TEM, DLS, FTIR, XRD and XPS. Shapes of AuNPs were observed predominantly spherical with average projected and hydrodynamic diameters of 9.49 and 168 nm respectively. The role of phytochemicals acting as active reducing and capping agents has been recognized and explained by the establishment of the reaction mechanism. © 2021 Taylor & Francis Group, LLC.