Metal coordination compounds with different ligands get more and more attention to biotechnologists due to their ability to model biosynthetic processes in living cells, namely at very low concentrations. As xenobiotic to living organisms, these compounds create an oxidative stress of different intensity, which often is associated with initial increase in antioxidant activity of cells. In this way, coordination compounds may serve as a model for directed synthesis of antioxidant components in the objects of biotechnological interest. There have been used 4 Fe(III) coordination compounds with Schiff bases, obtained from condensation of 2,6-diacetylpyridine with isonicotinic acid hydrazides (H2L1) and nicotinic (H2L2) with formula [Fe(H2L)(H2O)2]X (H2L=H2L1, X=NO3 - (I), ClO4 (III); H2L=H2L2, X=NO3 (II), ClO4 - (IV) and structure of the complex cation (Fig.1), which were manifested as modulators of antioxidant activity of Nostoc biomass. The compounds have been added to the nutrient medium in various concentrations to induce an oxidative stress in cyanobacterium Nostoc linckia. The biomass was collected at day 10 of the cultivation cycle. The aqueous extracts were obtained by extracting in water in proportion 5:1 (mg:ml). There was carried out the evaluation of antioxidant potential of the water-soluble fraction with phycobiliproteins as major components, by applying ABTS free radical scavenging assay (2,2-azinobis 3 ethylbenzothiazoline6-sulphonic acid). The content of phycobiliproteins in the extracts from Nostoc biomass increased in all application instances of Fe(III) coordination compounds. The highest values were determined when applying the compound I in concentration of 15 mg/L, which caused an increase of phycobilins by 132% compared to control biomass. A significant increase in phycobilins content was recorded, when Nostoc linckia culture was grown on the medium with compound III in concentrations of 5 mg/L and 10 mg/L. The phycobilin biosynthesis was higher by 80% and 100%, respectively. In all these experimental variants, the antioxidant activity of water extracts from Nostoc biomass recorded ABTS radical inhibition of about 80%. The inhibition of ABTS radical was 77%, especially for low concentrations of 1mg/L and 5mg/L coordination compound II. The phycobiliproteins exceeded by 60-70% the values of the control. When applying compound IV, ABTS ranged within the limits of control 62%. The amount of phycobiliproteins increased by 30-40% compared to standard biomass. Thus, the adding of coordination compound has led to the intensification of phycobilins accumulation in Nostoc biomass and the increasing of antioxidant activity.