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Cosmos sulphureus is an adventitious species for Europe and Ukraine in particular. It originates from Central and South America, where it grows in tropical and subtropical climates. The climatic conditions of Kyiv are characterized as temperate, with an absolute temperature minimum of –32.2 °C, an absolute maximum of +39.9 °C, and average annual rainfall of 649 mm. Plants were analyzed in the flowering phase, divided into inflorescences, leaves, stems, and roots, dried at +35 °C and then extracted with methanol and water. The determination of the antiradical activity was carried out according to a modified method using a DPPH (2,2-diphenyl-1-picrylhydrazyl) radical inhibition reaction. The highest antiradical activity was detected in inflorescences (59.60–81.81 % inhibition) and leaves (79.81–89.12 % inhibition). Stem extracts had an average level of inhibition (19.63–65.93 %), and root extracts showed only 2.54–39.46 % inhibition. Correlation analysis showed a strong relationship between leaves and stems (r = 0.84), leaves and roots (r = 0.81), and stems and roots (r = 0.91). Extracts of C. sulphureus plants grown in temperate climate were found having a high antioxidant potential but lower than that reported for tropical and subtropical regions. It was found that higher intensity of coloration of marginal florets of the capitulum does not correlate with a higher antiradical activity. Methanolic and water extracts of inflorescences of the genotype CSCO-368812 with intensilly colored perianth inhibited only 59.60 % and 71.50 % of radicals, while similar extracts of the genotype CS-361294 with lighter florets inhibited 71.17 % and 81.81 % of radicals, respectively. Instead, there was a difference in antiradical activity depending on applied extractant. Methanolic extracts of vegetative organs (leaves, stems, roots) prevail over water extracts in terms of their antiradical activity. However, water extracts of inflorescences of both genotypes demonstrated higher level of antiradical activity.

Flavonols, anthocyanins, and chalcones were determined during the flowering phase in two genotypes of Cosmos sulphureus (regular species and its cultivar ‘Cosmic Orang’) grown in the М.М. Gryshko National Botanical Garden in Kyiv. Inflorescences, leaves, stems, roots, and separated ray and disc florets were dried and crushed to prepare extracts following three different techniques. In particular, with 80 % (v/v) ethanol following Andreeva & Kalinkina (2000), 3.5 % HCl following Kriventsov (1982), and 0.1 N HCl following Udovenko (1988). The absorbance of flavonoids was measured at 390 nm wavelength for flavonols, 530 nm – for anthocyanins, and 364 nm – for chalcones. The highest content of flavonols was found in inflorescences of both genotypes (87.79 ± 1.64 and 87.99 ± 1.75 mg / 100 g of dry weight (DW), respectively). The content of anthocyanins was found to be ranked by overground organs: inflorescences > leaves > stems. In particular, the content of anthocyanins in the inflorescences of these two genotypes was 188.95 ± 5.20 and 177.14 ± 6.81 mg / 100 g DW, respectively. In the leaves, the content of anthocyanins was 61.32 ± 1.97 and 41.33 ± 2.27 mg / 100 g DW, respectively. In the stems, the content of anthocyanins was 31.63 ± 1.16 and 25.31 ± 0.95 mg / 100 g DW, respectively. In the roots, the anthocyanins were not detected. Among the flavonoids, the highest content, in general, was found for anthocyanins. Similarly, chalcones were also localized in overground organs only and mostly in the inflorescences (39.65 ± 1.25 and 37.93 ± 0.88 mg / 100 g DW, respectively). The content of chalcones in the leaves and stems was much lower than the content of the anthocyanins and flavonols; it significantly varied for two investigated genotypes. During the detailed investigation of the flavonoids content in different parts of the inflorescence, it was found that disc florets in both genotypes had fewer flavonoids than the ray florets.