The hexane fractions of the marine cyanobacteria: Leptolyngbya sp. and Limnothrix sp., collected from Arabian Sea were found to display promising antioxidant properties than their ethyl acetate fraction during radical scavenging ABTS/DPPH assays (IC50=30/330 and 60/260 µg ml-1 respectively). Phytochemical analyses of the fractions indicated presence of carbohydrates, flavanoids and steroids in both organisms. The hexane fraction of Limnothrix sp exhibited higher UV-Vis (300-450 nm) absorption, indicating presence of aromatic antioxidant compounds like flavanoids. This fraction was relatively non-toxic towards mouse fibroblast 3T3 cells (IC50 400 µg ml-1) and in fact, protected live cells from UV induced intracellular reactive oxygen species (ROS) stress. On the contrary, the hexane fraction of Leptolyngbya sp. had lower UV-Vis absorption, richer in alkaloids and also more cytotoxic (IC50 200 µg ml-1) towards the mouse fibroblast 3T3 cells. In short the hexane fraction of Limnothrix sp. is a safe antioxidant additive for food and healthcare products. On the other hand, the hexane fraction of Leptolyngbya sp. is rich in alkaloids and was cytotoxic, with potential application in cancer therapy.