The objective of this work was to study the occurrence of antioxidant compounds in the cyanobacterium Anabaena PCC 7119, as part of our research on new antioxidants for use in food preservation. Anabaena PCC 7119 was grown under light intensities of 100 (I), 200 (II) and 300 (III) μMoles of photons/m².seg. Biomass was obtained in the exponential and stationary phases and was extracted with methanol. Extracts were fractionated on a charcoal column and the fractions were tested for antioxidant activity using thin layer chromatography β-carotene bleach test. The higher biomass production was obtained with light intensity II. Antioxidant activity was found in the extracts of all growth phases for light intensities I, and II but not for III. The ability of the extracts to prevent soybean oil oxidation was also tested. Biomass extracts obtained from both exponential and stationary phases under conditions I and II displayed antioxidant and synergistic activities in soybean oil. Moreover, when tested in oil used in frying potatoes, the extracts displayed heat stability. The extract obtained from biomass III did not show such activities suggesting that excess light decreased the production of antioxidant compounds. Our results demonstrate the potential of biotechnology of cyanobacteria in the production of new antioxidants for food preservation.