The synthesis of silver (Ag) nanoparticles using by pedicellamide (A), isolated from Piper pedicellatum C.DC leaf is demonstrated here. TEM analysis revealed that the Ag nanoparticles predominantly form spherical in shape. The compound 'A' act as a reducing, stabilizing and capping agent. The reaction mechanism was established by using density functional theory (DFT). Photocatalytic property of the Ag nanoparticles is investigated by degradation of Methyl Red (MR) dye under UV light. The kinetic, reaction mechanism and rate constant of photocatalytic degradation of MR was evaluated. The results show that Ag nanoparticles have suitable photocatalytic activity for the degradation of MR dye.