Nanostructures of noble metals were immensely studied owing to their eminent salient features like morphology, controllable size dispersity and surface chemistry. Herein, we report a facile and eco-friendly route to synthesize gold nanoparticles (CGAuNPs) within a shorter period of time using the aqueous fruit extract of Couroupita guianensis Aubl. (CGFE) as a potential bioreductant to reduce Au3+ ions into their nanoscale counterparts. Growth of CGAuNPs generates a shift in the color of reaction medium due to the excitation of surface plasmon resonance (SPR) which produces an intense absorbance peak at 530nm in UV–Visible spectroscopy. Fourier transform infrared spectroscopy (FTIR) confirms the active role of water soluble phenolic compounds in achieving the reduction and stabilization of CGAuNPs. Additionally, transmission electron microscope (TEM) and X-ray diffraction (XRD) studies revealed that the synthesized CGAuNPs were anisotropic face centered cubic crystalline in nature, having an average size of 26±11nm. Dynamic light scattering (DLS) and Energy dispersive spectroscopic (EDAX) results were proved that the synthesized CGAuNPs were free from contaminants and they were stable, possessing negative electric charge without aggregation. On the other hand, in vitro antioxidant assays demonstrate that the aqueous CGFE and formulated CGAuNPs possess extraordinary antioxidant properties. Hemocompatibility assay depicts the safe nature of synthesized CGAuNPs for biomedical applications. Thus, the results of present study will be useful to synthesize AuNPs instantly via green chemistry route for its valuable applications in nanomedicine. Display omitted •Instant green synthesis of anisotropic gold nanoparticles using fruit extract of C. guianensis•Physio-chemical characterization and identifying the role of phenolic antioxidants on functionalization of NPs•In vitro antioxidant and biocompatibility assessment of synthesized NPs