In this present study, an attempt was taken to investigate the antibacterial activity of Nyctanthes arbor - tristis. The seed and fruit extracts were used for their antibacterial screening. Melanin content and stability in fruits and seeds were studied with various factors like temperature, oxidants and metal ions. Chloroform and ethyl acetate extracts of fresh leaf, seeds and fruits were shown significant antibacterial activity against Gram negative bacteria (E. coli and K. pneumoniae) and Gram positive bacteria (S. aureus), where as dried extracts of chloroform and ethyl acetate shown significant antibacterial activity against Pseudomonas aeruginosa. Phytochemical analysis shows the presence of phytosterols. Phenolics compounds, tannins, flavonoids, cardiac glycosides, saponins and alkaloids in leaf, fruit, seed content. Steroids were present only in seeds. UV spectral studies have shown high content of melanin in seeds. Melanin content was stabilized by KmNO4 than K2Cr2O7. Melanin color was increased and preserved by metal ions like of Fe++, Mg++ and Zn++.