An experimental study of the structural and vibrational properties of sesquiterpene lactone cnicin using FT-IR, FT-Raman, UV–visible and NMR spectroscopies.

Highlights: [•] Cnicin was characterized by infrared, Raman, NMR and UV–visible spectroscopies. [•] The molecular structure of cnicin has a ten member’s ring with a chair conformation. [•] The γ-lactone ring of cnicin has a half-chair conformation. [•] The NBO and AIM studies show the high stability of cnicin. [•] A complete assignment of the 153 normal vibration modes for cnicin was performed. [Copyright &y& Elsevier]