Differential analysis of ginseng methanol extracts from different origins using FTIR and 2D-COS-IR spectroscopies

The quality of ginseng extracts is largely determined by the ginsenosides present in them. However, the high similarity among such extracts poses a considerable challenge to the rapid differentiation of their origins, which is critical for ensuring product quality. In this study, Fourier transform infrared (FTIR) spectroscopy, second-derivative infrared (SD-IR) spectroscopy and two-dimensional correlation spectroscopy coupled with infrared (2D-COS-IR) spectroscopy combined with chemometric methods (similarity analysis, dual-index sequence analysis, and principal component analysis) were applied to discriminate ginseng methanol extracts from ten different origins. FTIR spectroscopy confirmed the consistent core saponin structure of all samples but offered limited discriminatory ability; SD-IR amplified subtle static spectral differences through dual-index sequence analysis (DISA); and 2D-COS-IR, the most effective technique, achieved differentiation. The 2D-COS-IR synchronous spectra displayed sample-specific auto-peak distributions and intensity variations, reflecting the distinct thermal responses of functional groups of the extracts from different origins. The 2D-COS-IR asynchronous spectra showed unique cross-peak patterns, and combined with the Noda's rules, these spectra revealed divergent molecular response sequences to thermal perturbation across different samples. The integrated FTIR, SD-IR and 2D-COS-IR spectroscopic strategy enables the rapid, non-destructive differential analysis of ginseng methanol extracts, providing a reference basis for the differentiation of other similar samples.