Stigmata of Crocus sativus L. were extracted in water, and the extract was analyzed by using a high-pressure liquid chromatography (HPLC) method. The carotenoids of saffron [ cis and trans glycosyl esters of crocetin or crocins (CRCs)] were isolated, and the two major isomer compounds (all- trans -digentiobiosyl crocetin and 13- cis -digentiobiosyl crocetin) were characterized spectroscopically with ultraviolet-visible (UV-vis), Fourier transform (FT)-Raman, and 1H NMR spectroscopies. The 13- cis compound showed in a UVvis spectrum an additional peak at 330 nm, in an FT-Raman spectrum the presence of a peak at 1138 cm 1, and in the 1H NMR downfield shifts of protons 12 and 15 and an upfield shift of proton 14, with respect to the all- trans isomer, according to differences in their skeletal structures. These features are shown also by the profile of their two-dimensional spectra.
Manolis K. Assimiadis, Petros A. Tarantilis, and Moschos G. Polissiou, "UV-Vis, FT-Raman, and 1H NMR Spectroscopies of cis - trans Carotenoids from Saffron ( Crocus sativus L.)," Appl. Spectrosc. 52, 519-522 (1998)