Chemical constituents of Centaurea dissecta Ten. and sesquiterpenes chemotaxonomic significance

The phytochemical investigation of Centaurea dissecta Ten. led to the isolation of thirty-two compounds of diverse chemical classes including two sesquiterpene lactones (1, 2), two sesquiterpenes (3, 4), twelve flavonoids (5–16), one lignan (17), twelve phenols (18–29), one triterpene (30) and two phytosterols (31, 32) from the EtOAc and n-BuOH soluble fractions of the 70% aqueous ethanol extract. Furthermore, the phenolic and flavonoid contents were measured for the petroleum ether, EtOAc and n-BuOH soluble fractions. The chemical structures of these compounds were determined by using a combination of NMR spectroscopic and mass spectrometry (ESI-MS) analyses, as well as by comparison with literature values. Only apigenin (15) was isolated previously from Centaurea affinis, and all other compounds were isolated for the first time from this species. Noticeably, ethyl ferulate (20), ethyl caffeate (21), synapyl aldehyde (22), coniferyl aldehyde (23), 2,3-dihydroxy-1-(4-hydroxy-3,5-dimethoxyphenyl)-1-propanone (24), and C-veratroylglycol (25), have not been reported from the genus Centaurea. All compounds have been previously isolated in various plants belonging to the Asteraceae family. Meanwhile, the chemotaxonomic significance of the isolated compounds was summarized.