Various constituents of plant, bacteria, fungi, and biopolymer responsible for the reduction of silver nitrate to AgNPs.

Source	Components responsible for the reduction of silver nitrate	Mechanism for the synthesis
Plants	Flavanoids, terpenoids, alkaloids, polyphenols, alcohol, phenolic acids, antioxidants, vitamins	Electrostatic interaction between the functional groups of respective constituent of plant extract and Ag+ ion
Fungi	Proteins, enzymes, NADH, NADPH, peptides, nitrogenous biomacromolecules, napthoquinones, anthraquinones	Intracellular and extracellular synthesis of AgNPs
Biopolymers	Chitosan, lignin, polypeptides, alginate, cellulose, protein	Electrostatic interaction between Ag+ ion and polar groups attached to polymer