Distinction of eight Lycium species by Fourier-transform infrared spectroscopy and two-dimensional correlation IR spectroscopy

Eight species of Lycium fruits were differentiated by Fourier-transform infrared spectroscopy (FT-IR), second derivative IR spectra and two-dimensional correlation infrared spectroscopy (2D-IR). Their entire infrared spectra in the range of 4000–400 cm−1 were generally similar based on the peaks position and intensities. The findings indicated that the chemical constituents in these species of herbs were not distinctively different. However, variation in peak intensity were observed at about 2926, 2855, and 1745 cm−1 in the infrared spectra among these species for their easy differentiation. Much difference in their second derivative pattern among the eight species also provided information for easy differentiation. These species of Lycium fruits were further identified by their 2D-IR spectra. The findings provide a rapid and new operational procedure for the differentiation of different species of Lycium plants. The visual and colorful 2D-IR spectra can provide dynamic structural information of chemical components in analyte and demonstrated as a powerful and useful approach for the identification of herbs.