In this study, the structure of the purified extracellular eumelanin pigment isolated fromStreptomycesspp. was elucidated by detailed analysis via two different spectroscopic techniques (FT-IR and NMR). In vitro antiproliferative effects of eumelanin were evaluated on HeLa cell line. These experiments were carried out with the evaluation of the parameters including cell viability, cell index, and mitotic index. With the cell viability and cell index, IC50 concentration of eumelanin was determined as 10 mu M. This result showed that the IC50 concentration of eumelanin decreased the values of cell viability, cell index and mitotic index. These changes are statistically significant (p < 0.01). The ability of the dissolved eumelanin (250 mu g mL(-1)) to scavenge free radicals was determined via DPPH and ABTS and was shown to be about 87.73% and 75.2%, respectively, compared with standard antioxidants. It was observed that dry weights of eumelanin yield among the selected strains ranged from 160 to 240 mg L-1. The strain with the highest production potential was selected for 16S rDNA sequence analysis and, accordingly, the selected strain BSB49 was identified asStreptomyces parvusand the sequence analysis results were deposited in NCBI under accession number MK894155.