Abstract: In the study it is shown that in the territory of Buryatia the badantolstolistic is widespread, the analysis of its chemical composition indicates the presence of a complex of compounds related to natural antioxidants: tocopherols, carotenoids, phospholipids, flavonoids, anthocyanins. When carrying out researches of antioxidant properties of leaf extracts of thick-leaved balm, the method of aqueous extraction of Biologically Active Substances (BAS) from vegetable raw materials was chosen. In the composition of the dry substances of the extract the largest amount contains tannic substances and phenolic compounds. Phenolic compounds and proteins account for about 40%, reducing sugars account for 20% of the dry residue organic acids for 3%. The extract contains carotenoids ascorbic acid as well as a large amount of minerals including trace elements. In this study, we studied the antioxidant activity of water extracts from the leaves of thick-leafed horseradish collected at different periods of vegetation. The extracts studied had a high ability to absorb free radicals but the extract from the green leaves of badan had a greater antiradical activity at a concentration of 125 mg/cm³ and had a minimum E_C50 of all the extracts. In addition, the extracts showed the ability to chelate iron ions in particular, the extract from the green leaves of the badan showed the greatest restoring force (0.97 mmol F^e2+/1 mg). According to the presented data, plant extracts from the leaves of badan have a pronounced antiradical and chelating activity. Extracts from green leaves of badan are the most promising for further research which in turn opens up new ways of using it as components of food products: beverages, confectionery and bakery products, meat and fish products and functional purpose.