UV-Vis, FT-Raman, and 1H NMR Spectroscopies of cis-trans Carotenoids from Saffron (Crocus sativus L.)

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Abstract
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 UV-vis 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 uptield 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.