Analyses and identification of the chemical constituents of the Uighur formulation Baixuan Xiatare using three-stage infrared spectroscopy

Objective: To identify, rapidly and accurately, the chemical composition of the traditional Uighur formulation Baixuan Xiatare (BXXTR-FU).

Methods: We investigated if application of three-stage infrared (IR) spectroscopy enabled identification of the main chemical constituents (and their origins) in BXXTR-FU.

Results: The characteristic peaks of herbal material(s) and BXXTR-FU were assigned. In Fourier transform-IR (FT-IR) spectroscopy of BXXTR-FU, peaks at 1616 and 1605 cm-1 of BXXTR-FU were considered to denote anthraquinones and their derivatives; 1066 cm-1 was regarded as the characteristic absorption peak of resin glycosides. In second-derivative IR (SD-IR) spectroscopy, the main carbonyl types of BXXTR-FU in the range 1743-1636 cm-1 were assigned: 1651 cm-1 belonged to the carbonyl stretching vibrations of flavonoids and chromones; 1717 cm-1 belonged to tannins; 1699 cm-1 belonged to carboxylic acids; 1636 cm-1 belonged to anthraquinones and their derivatives. SD-IR spectroscopy further confirmed that the characteristic absorption peaks at 1636, 1618 and 1603 cm-1 could be used as markers that BXXTR-FU contained anthraquinones and their derivatives. Synchronous 2D-IR correlation spectra of chemical groups further confirmed the results of FT-IR and SD-IR spectroscopy.

Conclusion: Our study strongly supported the necessity and importance of three-stage IR spectroscopy owing to its rapid and accurate identification of herbal formulations.