Mass spectrometry imaging is a frontier technique which connects classical mass spectrometry with ion imaging. Various types of chemicals could be visualized in their native tissues using mass spectrometry imaging. Up to now, the most commonly applied mass spectrometry imaging techniques are matrix assisted laser desorption ionization mass spectrometry imaging, desorption electrospray ionization mass spectrometry imaging and secondary ion mass spectrometry imaging. This review gives an introduction to the principles, development and applications of commonly applied mass spectrometry imaging techniques, and then illustrates the application of mass spectrometry imaging in the investigation of traditional Chinese medicine. Recently, mass spectrometry imaging has been adopted to explore the spatial distribution of endogenous metabolites in traditional Chinese medicine. Data collected from mass spectrometry imaging can be further utilized to search for marker components of traditional Chinese medicine, discover new compounds from traditional herbs, and differentiate between medicinal plants that are similar in botanical features. Moreover, mass spectrometry imaging also plays a role in revealing the pharmacological and toxicological mechanisms of traditional Chinese medicine.

The accuracy of near-infrared quantitative models for traditional Chinese medicine is restricted by the matrix, low-concentration markers, and overlapping spectral bands. Competitive adaptive reweighted sampling, a recently developed algorithm, selects an optimal combination of multicomponent spectral data. In this article, the performance of this method was evaluated through the analysis of traditional Chinese medicine. The near-infrared spectra of the pharmaceutics were obtained and the concentration of puerarin was determined. After optimization of spectral pretreatment methods, competitive adaptive reweighted sampling was performed in each dataset to select key wavenumbers. Sixty-eight, thirty, and eight variables were selected for the raw material, intermediate product, and final product, respectively. Partial least squares models were constructed based on the selected variables. Enhanced accuracy was obtained using the competitive adaptive reweighted sampling-coupled models. The results indicated that competitive adaptive reweighted sampling improved the accuracy and simplified calibration while offering a new approach for the rapid and nondestructive analysis of traditional Chinese medicine.

Like chemical drugs, research and development of herbal medicine also have a need to resolve enantiomers. To help illustrating the antiviral bioactivity of Isatidis Radix, a widely used traditional Chinese medicine (TCM), supercritical fluid chromatography (SFC) was used for analytical and preparative separation of (R,S)-goitrin, which was reported as the active ingredient of the herbal. Improved resolution was achieved on Chiralpak IC column, using acetonitrile as the organic modifier, representing a tenfold increase in speed, compared to the previous normal phase HPLC (NPLC) method. The newly developed chromatographic method was validated in terms of linearity, precision, limit of detection (LOD), and limit of quantitation (LOQ). Scale-up purification of (R)-goitrin and (S)-goitrin was performed on a preparative column with >90% total recovery. The absolute stereochemical assignment of the purified isomers was determined through optical rotation study. This attempt explored SFC’s application in chiral research of traditional Chinese medicine.