In the present work, Cu 4 O 3 nanoparticles were prepared by biosynthesis method using Razma seeds and copper sulfate as a precursors. The synthesized Cu 4 O 3 nanoparticles were characterized using various analytical tools such as XRD, FTIR, UV-Vis, SEM and TEM. The average crystallite size of the prepared Cu 4 O 3 nanoparticles was calculated by Debye-Scherrer's equation and found to be 13 nm. The TEM images clearly reveal the average size of the particles is 27 nm. Antibacterial activity of Cu 4 O 3 nanoparticles was tested against Gram-positive (Staphylococcus aureus) and Gram-negative (Escherichia coli) bacteria by agar well diffusion method. The cytotoxic activity of synthesized Cu 4 O 3 nanoparticles was examined against human prostate cancer cells (PC-3). The prepared NPs show the significant antioxidant activity through scavenging of 1,1-diphenyl-2-picrylhydrazyl free radicals.