Quantitative analysis of sesquiterpene lactone cnicin in seven Centaurea species wild-growing in Serbia and Montenegro using 1H-NMR spectroscopy

H-NMR spectroscopy was applied for the quantitative analysis of cnicin, a bioactive germacranolide type sesquiterpene lactone, in the aerial parts of seven wild-growing Centaurea species collected in Serbia and Montenegro. The analysis was performed by comparison of the integral of the one-proton signal of cnicin (H-13, δ 5.75) with that of the two-proton singlet (δ 6.98) of 2,6-bis(1,1-dimethylethyl)-4-me- thylphenol (BHT), used as the internal standard. Cnicin, within the concentration range 1.06-6.12 mg/g, calculated per weight of the fresh plant material was detec- ted in six species, the exception being C. salonitana. This method allows the rapid and simple quantification of cnicin without any pre-purification step.