Discrimination and characterization of Panax polysaccharides by 2D COS-IR spectroscopy with chemometrics

In this study, a novel two-dimensional correlation infrared spectroscopy (2DCOS-IR) is presented to rapidly characterize and discriminate polysaccharides in Panax ginseng (PGP), P. notoginseng (PNP), and P. quinquefolius (PQP) using attenuated total reflection Fourier transform infrared spectroscopy-based on single-characteristic temperature as the external disturbance (2D-sATR-FTIR). Compared with two existing 2DCOS-IR methods based on gradient heating pathways using KBr pellet (100 min; 2D-KBr-FTIR) and attenuated total reflection (30 min; 2D-gATR-FTIR), the new procedure took an average of just 2 min to finish a sample measurement, which resolved previously tedious and time-consuming dilemmas. It offered advantages in the quality evaluation of natural polysaccharides and featured nondestructive, high-throughput, and high-efficiency characteristics. An intuitive analysis of the 2D-sATR-FTIR demonstrated that PNP was first identified because it had fewer auto-peaks. Posteriorly, PGP and PQP were distinguished according to the ratio of the auto-peaks 6 and 9, with the former greater than 1 and the latter less than 1. Furthermore, characteristic auto-peaks 1, 5, and 6 were unambiguously determined as Quality-markers using PCA and PLS-DA for visualized identifications. LDA was successfully used to establish a predictive model of the PGP, PNP, and PQP based on the positions and intensity of these three characteristic auto-peaks.