Classification and identification of TCM by macro-interpretation based on FT-IR combined with 2DCOS-IR

Abstract

An approach, macro-interpretation based on FT-IR and 2DCOS-IR, has been developed for TCM classification and identification. It has been noted that every TCM has respective unique IR and 2DCOS-IR macro-fingerprints, every category (protein-rich, oil-rich, tannin-rich, inulin-rich, starch-rich, sucrose-rich and stachyose-rich) of TCMs, however, has common macro-fingerprints in specific wavenumber regions. Particularly, protein-rich TCMs have two strong absorption bands of amide I (∼1630 cm⁻¹) and amide II (∼1560 cm⁻¹) in the range of 1680–1500 cm⁻¹; oil-rich TCMs generally have characteristic regions with strong autopeaks around 2920 cm⁻¹, 2852 cm⁻¹ and 1740 cm⁻¹; starch-rich TCMs have a common pattern of positively correlated strong autopeak cluster (1139 cm⁻¹, 1120 cm⁻¹, 1102 cm⁻¹, 1070 cm⁻¹, 955 cm⁻¹, 907 cm⁻¹, 887 cm⁻¹) in the saccharide vibration regions; inulin-rich TCMs have a tower-like fingerprint with the strongest peak around 1033 cm⁻¹ in the region of 1200–800 cm⁻¹ in IR spectra and a 3*3 positively correlated strong autopeak cluster (1006 cm⁻¹, 954 cm⁻¹, 893 cm⁻¹) in 2DCOS-IR spectra. 2DCOS can enhance the spectral resolution in discriminating TCMs with high similarity in IR spectra. Based on the results of IR and 2DCOS-IR spectral macro-interpretation, TCM classification and identification can be achieved as general character for classification, specific character for identification.