The data on the phytochemical composition and biological activity for flowering plant extracts of the genus Centaurea (Knapweed)—cornflower (Centaurea cyanus L.), brown knapweed (Centaurea jacea L.), and greater knapweed (Centaurea scabiosa L.), which are typical representatives of the flora in the middle belt of the Russian Federation, were obtained. For the first time, biologically active substances such as pyranone, coumaran (2,3-dihydrobenzofuran), and 5-hydroxymethylfurfural were identified in ethanol and methanol extracts of Centaurea scabiosa L. by gas chromatography–mass spectrometry. Catechol and α-amyrin were the major components of the ethanol extract from Centaurea cyanus L., and flavone was the major component of Centaurea jacea L. flower extract. The greatest antimicrobial activity against phytopathogens was detected in Centaurea scabiosa L. when extracting freshly harvested flower biomass with methyl tert-butyl ether at room temperature: the minimum inhibitory concentrations were 60–120 µg/mL, the minimum fungicidal concentration was 120 µg/mL, and the minimum bactericidal concentration was 250 µg/mL. The low antioxidant activity of the studied plant extracts was established using the maximum values of Centaurea jacea L. Ethanol extract of Centaurea cyanus L. flowers had low antimicrobial and antioxidant activity. The extracts showed no phytotoxicity to garden cress germination but inhibited the growth of juvenile plants, especially roots. The greatest phytotoxic effect was revealed with methyl tert-butyl ether, where the depression of growth indicators was 35% or more.

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Researchers are attracted to the wide-ranging, useful components in Aronia melanocarpa berries. They are searching for the most effective ways to extract the active substances that can enhance the body’s protective properties. The current study presents detailed information about the extracts from A. melanocarpa fruits frozen and dried under mild conditions and their chemical composition. In Wistar rats with induced immunosuppression, the effect of chokeberry fruit extracts on the leukocyte formula, phagocytic activity, and cytokine system was studied. It was shown that the A. melanocarpa frozen fruit extract contains more anthocyanins, sugars, and ascorbic acid, and has a more pronounced antioxidant activity determined by the ability to bind APPH-radicals. Moreover, the extract showed membrane-protective and cytoprotective properties against RPMI-1788 cell line. The extract from dried raw material shows a higher antioxidant activity due to the ability to bind DPPH-radicals. It was revealed that extracts from A. melanocarpa fruits promote rapid immune system recovery in rats, normalize the leukocyte count, and improve monocyte and neutrophil phagocytic indicators. Research on the cytokine profile revealed that the anti-inflammatory properties in A. melanocarpa extracts were more pronounced in dried extracts. For several cytokines, a normalization of quantity was noted.

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