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Antimicrobial properties of ethanol and water extracts from eight Asteraceae species were investigated against three Gram positive (Staphylococcus aureus, MRSA and Bacillus cereus) and two Gram negative (Escherichia coli and Salmonella typhimurium) bacterial strains. Ethanol extracts from Centaurea scabiosa, Arctium minus, Taraxacum officinale, Centaurea nigra and Cirsium palustre demonstrated antimicrobial activity against strains of S. aureus, MRSA and B. cereus (MIC=187.5-365μg/ml). Ethanol extracts also had higher antioxidant activities and phenolic content demonstrating a link between these compounds and the bioactivity of these extracts. Further investigation into the phenolic content of ethanol extracts using UPLC-MS/MS lead to the identification and quantification of numerous phenolic compounds in all species including; 18 from Cirsium arvense, 16 from Cirsium vulgare, 19 from C. palustre, 15 from C. nigra, 17 from C. scabiosa, 14 from Sonchus asper, 17 from A. minus and 11 from T. officinale.

It was found that weak chemiluminescence of manganese(IV)-hexametaphosphate-formaldehyde system was greatly enhanced by plant polyphenolic compounds. Based on this finding, a new flow injection chemiluminescence method (FI-CL) was developed for the determination of the total content of polyphenols in plant extracts. The calibration graph obtained for standard solutions of 6-hydroxyluteolin 7-O-glucoside (6OHLG) was linear in the range 0.001-0.8 μg mL(-1). The method was simple, rapid (203 samples h(-1)) and sensitive with a detection limit of 0.25 ng mL(-1). The FI-CL method was successfully applied to the determination of the total polyphenols content (as 6OHLG equivalents) in methanolic, ethyl acetate and aqueous extracts from leaves of Cirsium palustre (L.). Two types of solvent extraction methods (reflux and ultrasound assisted extraction) were used and compared in terms of extraction efficiency. A positive, significant linear correlation between the results obtained by FI-CL method and spectrophotometric methods was observed.