Algae have being investigated as a possible source of powerful pharmacological compounds to combat cancer cells. Following that, the MTT assay was used to assess the extracted compounds. Several chemicals were extracted and purified from C. vulgaris using chromatographic methods, and their structures were established using spectroscopic investigation. Using the MTT assay, these substances were then tested for their cytotoxicity against human cancer cell lines. The strongest chemical displayed selective cytotoxicity against cancer cells with low toxicity towards normal cells.The most active substance demonstrated little cytotoxicity towards normal cells and selective cytotoxicity towards cancer cells