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

H-1-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, delta 5.75) with that of the two-proton singlet (delta 6.98) of 2,6-bis(1,1-dimethylethyl)-4-methylphenol (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 detected in six species, the exception being C. salonitana. This method allows the rapid and simple quantification of cnicin without any pre-purification step.