In one of the aspect of the invention a method for isolation of bio-reducing agents as an aqueous extract is provided from the tuber of G. superba the bio-reducing agent in the aqueous extract is having G. superba is reported to contain various phytochemicals like alkaloid, flavonoids, glycosides, phenols, saponins, steroids, tannin and terpenoids. Flavonoids and phenolics play a key role in the bio-reduction of metal ions to nanoparticles in the reaction mixture, reducing sugars as agent In the other aspect of the invention the group 11 elements of the periodic table reacted with the aqueous extract of tubers of G. superba at an elevated temperature and the formation of metal nanoparticles is monitored as function of change in color of metal ion reaction mixture with aqueous extract of tuber of having G. superba by UV-Visible spectrophotometer
