Secondary metabolites from Chrysanthemum coronarium (Garland) flowerheads: Chemical composition and biological activities

► The chemical composition of the essential oil of Chrysanthemum coronarium flowerheads was investigated. ► cis-Chrysanthenyl acetate, trans-chrysanthenyl acetate, (E)-β-farnesene, germacrene-D and camphor were the major components. ► The oil had a weak antioxidant and antimicrobial activities. ► The aqueous extract showed a strong and selective allelopathic activity against weeds. ► The main bioactive components di-cafeoylquinic acids isomers, luteolin-7-O-glucoside, myricetin-3-O-galactoside and tricin. The essential oil of Chrysanthemum coronarium (Garland) flowerheads was analyzed by gas chromatography–mass spectrometry and essayed for its in vitro scavenging activity on 1,1-diphenyl-2-picrylhydrazyl (DPPH) and its antimicrobial activities against Escherichia coli, Salmonella typhymurium, Candida albicans, Bacillus cereus and Staphylococcus aureus. The aqueous extracts were tested for their allelopathic properties on seed germination and seedling growth of two annual weeds (Sinapis arvensis and Phalaris canariensis) and two crops (Triticum durum and Zea mays) and the identity of the phenolic components was determined by using HPLC–PDA-MS. A total of 40 components, representing 96.58% of the total oil were identified, and the most plentiful constituents were found to be cis-chrysanthenyl acetate (21.82%), trans-chrysanthenyl acetate (12.78%), (E)-β-farnesene (8.97%), germacrene-D (8.92%) and camphor (6.03%). The oil was unable to reduce the DPPH radical, while it exhibited a good antimicrobial activity against the gram-positive bacteria B. aereus and S. aureus. The aqueous extracts suppress the germination and reduce the seedling growth of the target species. The phytotoxic effect was found to be selective towards weeds with the effects being more pronounced in S. arvensis and P. canariensis. HPLC–PDA-MS analysis allowed the identification of chlorogenic acid acid, di-cafeoylquinic acids isomers, rutin, luteolin, luteolin-7-O-glucoside, myricetin-3-O-galactoside and tricin. The latter components were reported in C. coronarium for the first time. It is suggested that the identified components may be at least, a key factors in the observed phytotoxic activity and the data presented may contribute to the development of naturally occurring herbicides.