In connection with the increase in the impact of unfavorable environmental factors on biological objects, including plants used in agriculture, it is important to find adequate ways to counteract current stressors (climate change – extreme temperature effects, drought and excessive watering of soils, accumulation of heavy metals and other). Among the factors that counteract stress, natural biocompatible biologically active compositions containing endogenous antioxidants are of great interest. The aim of the study was to justify the possibility of using primroses as a biosubstance containing endogenous antioxidants to reduce and prevent the effects of oxidative stress. The object of the study were early-flowering plants – Allium ursinum L., Primula véris L., Állium schoenoprásum L. In the primrose leaves, the content of endogenous antioxidants (diene conjugates, the sum of flavonoids, the sum of phenolic compounds, ascorbic acid), the activity of the antioxidant system (the content of lipid peroxidation products, diene conjugates) was determined. The investigated parameters were determined by the spectrophotometric method. Results of the study. Analyzing the changes in antioxidant activity of early flowering plants, it has been established that they are characteristics of structural-functional adaptations and vary insignificantly depending on the place and conditions of growth and the type of plant population, which makes it possible to cultivate them without loss of value characteristics as an antioxidant biosubstance and conservation of biodiversity of protected natural populations. The results of the study can be used to create from primrose extracts possessing antioxidant effect, which are affordable and simple in their implementation and the ability to further process biological objects with this substrate, increasing their stress resistance to unfavorable factors.