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

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.