Green Synthesis of Gold and Silver Nanoparticles Using Opuntia dillenii Aqueous Extracts: Characterization and Their Antimicrobial Assessment

Table 1

List of reagents used for identification of secondary metabolites in extracts.

Phytochemicals	Method	Results for the presence of an ingredient
Alkaloids	0.5 g plant extract+2% H2SO4+Dragendorff reagent	Orange red ppt
Tannins	Filtered extract+drops of ferric chloride	Dark green color
Glycosides	Extract+HCl+NaOH+Fehling reagent	Appearance red ppt
Saponins	Extract+H2O (boiled)	Frothing occur
Anthraquinones	0.5 g extract+10% HCl (boil) and then add chloroform+10% ammonia and heat	Appearance rose pink color
Flavonoids	0.2 g extract+NaOH+HCl	The yellowish color disappears on adding HCl
Steroids	0.3 g extract+acetic acid (heat)+H2SO4	Color change to green
Terpenoids	0.2 g extract+2 ml chloroform+3 ml H2SO4	Reddish brown color
Emodin	0.5 g extract+2 ml NH4OH+3 ml benzene	Appearance of red color
Anthocyanin and betacyanin	0.2 g extract+2NaOH (heat)	Appearance of bluish green color