The development of new routes and strategies for nanotechnology applications that only employ green synthesis has inspired investigators to devise natural systems. Among these systems, the synthesis of gold nanoparticles using plant extracts has been actively developed as an alternative, efficient, cost-effective, and environmentally safe method for producing nanoparticles, and this approach is also suitable for large-scale synthesis. This study reports reproducible and completely natural gold nanocrystals that were synthesized using Virola oleifera extract. V. oleifera resin is rich in epicatechin, ferulic acid, gallic acid, and flavonoids (i.e., quercetin and eriodictyol). These gold nanoparticles play three roles. First, these nanoparticles exhibit remarkable stability based on their zeta potential. Second, these nanoparticles are functionalized with flavonoids, and third, an efficient, economical, and environmentally friendly mechanism can be employed to produce green nanoparticles with organic compounds on the surface. Our model is capable of reducing the resin of V. oleifera, which creates stability and opens a new avenue for biological applications. This method does not require painstaking conditions or hazardous agents and is a rapid, efficient, and green approach for the fabrication of monodisperse gold nanoparticles. Graphical AbstractThe Virola oleifera reduction method for the synthesis of gold nanoparticles (AuNP’s)

Metallic nanoparticles synthesized by plant extracts and biomolecules represent one of the most promising frontiers in the antioxidants field. Plant compounds apart from act as reducing agents, also allow functionalizing these nanoparticles having multiple applications in different industries. However, the low reproducibility and the difficulty in size, shape and stability control have made it difficult to produce on a large scale. Here we report an optimization process to obtain gold nanoparticles (AuNPs) from green synthesis using a factorial design aiming to present a controlled synthesis using Virola oleifera as a reductant agent. We evaluate the influence of the reaction time, temperature, stirring rate, pH and extract concentration monitoring the Localized surface-plasmon resonance (LSPR) band shift (Δλ). The nanoparticles were characterized using Zeta potential, UV-vis, DLS, TEM, Raman spectroscopy, FTIR and XRD. The as-synthesized AuNPs were stable and homogenous, octahedral, monodisperse, and in shape and size and showed great antioxidant activity determined with ABTS+ and DPPH. Furthermore, these nanoparticles presented low cytotoxicity. Finally, using the factorial design, we were able to develop an optimal path for green gold nanoparticles with high antioxidant activity, low toxicity and good morphological characteristic.

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