Cirsium vulgare is a biennial plant from the family Asteraceae. Scientists have studied other species of Cirsium and found that these plants accumulate large amounts of phenolic compounds and amino acids. Essential amino acids are important for all life forms. It is also known that phenolic compounds often have particularly good antioxidant properties, so it was important to investigate this as well. The main goal of our research was to investigate how the chemical composition of the plant and antioxidant activity differ during the different phenological stages of the plant throughout the year.

The HPLC method was used for the determination of phenolic compounds in the ethanolic extracts of the first- and second-year raw material. Quantitative determination of amino acids was performed using the GC-MS method via derivatization with MTBSTFA. The antioxidant effect was determined using the CUPRAC method.

After carrying out a two-year quantitative determination of the active compounds from ethanolic extracts of Cirsium vulgare leaves, flowers, and roots, it was found that the highest yields were detected for chlorogenic acid and apigenin-7-O-glucoside. The highest yields of chlorogenic acid were found in extracts made from the leaves. In the raw material of the first year, higher yields of chlorogenic acids were determined during the mass flowering. The second year represented the phenological stage, i.e., the end of plant rest. The yield of apigenin-7-O-glucoside was found to be highest in the extracts of the leaves compared to other parts of the plant. The quantitative composition of amino acids in the flowers of the plant had the highest diversity and yields of amino acids compared to the extracts made from other parts. During the antioxidant test, it was found that the raw material, which was collected during the dormant period, had exceptionally high antioxidant activity.