Rapid discrimination of Panax notogeinseng of different grades by FT-IR and 2DCOS-IR

The herbal material of Notoginseng (the root of Panax notoginseng) is sold by “Tou” (the number of Notoginseng in every 500 g) to distinguish the grade. Normally the better quality, the few number of the “Tou” and the size of Notoginseng is bigger. In this study, three grades of Notoginseng harvested from Yunnan province were discriminated and identified by Fourier transform infrared spectroscopy (FT-IR) and two-dimensional correlation infrared spectroscopy (2DCOS-IR)). The correlation coefficient of IR spectra between the three grades of Notoginseng and starch are greater than 0.95 in the range of 1300–800 cm−1, means the main compositions of Notoginseng are starch polysaccharide. Also, when the size of Notoginseng is bigger, it may contain more polysaccharide. There is no difference in range of 815–1000 cm−1 of the 2DCOS-IR synchronous spectra of the three grades means polysaccharides possess good thermal stability. In the range of 1200–1300 cm−1 shows the inverse ration between the thermal sensitivity of C–O and the number of “Tou”. Combination with the 2DCOS-IR asynchronous spectra, the response speed of amino acid (1640 cm−1) on the thermal perturbation is the fastest, followed by nitrate (1384 cm−1); the response speed of polysaccharides (1079 cm−1) is the slowest. The result proved that the 2DCOS-IR could discriminate different grades of Notoginseng.