The present work reports a simple-economical procedure for the formation of silver nanoparticles by using controlled addition of concentration of cetyltrimethylammonium bromide (CTAB) as a capping agent, taking one-factor-at-a-time into consideration during the optimization process. Wet chemical method for silver(I) reduction has been used to synthesize nanoparticles using Andrographis paniculata. During the reaction, antioxidant property of biosystem reduces silver(I) to metallic silver(0) and CTAB encapsulates preventing the agglomeration, acting as barrier for the growth of the particle. The synthesised nanoparticle was characterised by powder X-ray diffraction, Fourier-transform spectroscopy, UV-Vis spectroscopy and SEM. The results showed that the silver nanoparticles doped with CTAB and its high crystallinity can be obtained using simple solvent method. The size of the nanoparticle by XRD, UV-Vis and SEM were found to be 0.897 nm, 45 nm and 18 to 43 nm, respectively. Tauc's plot of optical band gap suggested the movement of size towards quantum confinement for the synthesised nanoparticles was 2.25 eV. An antioxidant activity of A. paniculata and synthesized AgNps was studied by series of antioxidant assays. The nanoparticles were having antibacterial and antifungal activities when it was studied using Streptomycin and Ketoconazole as controls.