The invention provides stabilized, biocompatible gold nanoparticles that are stabilized with material from polyphenols- or flavanoids-rich plant material or reactive phytochemical components of the plant material. The gold nanoparticles of the invention can be fabricated with an environmentally friendly method for making biocompatible stabilized gold nanoparticles. In methods of the invention, an aqueous solution containing gold salts is mixed with polyphenols- or flavanoids-rich plant material. In preferred embodiment methods of making, an aqueous solution containing gold salts is provided. The aqueous solution is mixed with black tea, turmeric, curcumin or cinnamon or a similar naturally occurring polyphenols- or flavanoids-rich plant material. The gold salts react to form biocompatible gold nanoparticles that are stabilized with a coating of the polyphenols- or flavanoids-rich plant material. The black tea, turmeric, curcumin or cinnamon or similar naturally occurring polyphenols- or flavanoids-rich plant material can be a powder or can be in its root or bark form.