Monitoring the Chemical Transformation and Detoxification Process of Herbs during Processing by Maximum-Quantum Filter NMR Spectroscopy.

Processing is an ancient technique to make Traditional Chinese Medicine (TCM) more effective or less toxic; however, the traditional process control for processing is empirical, and it is highly desired to monitor chemical markers that are pharmacologically or toxicologically relevant to evaluate such processing practice, but this task is challenging due to the complexity of natural products. The processing of herbs is a classic case in TCM practice. Traditional processing operations, such as boiling or steaming, are needed to detoxify the herbs before their medicinal use, so holistic analysis of toxic substances is meaningful for safety assessment of the processed herbs. In the present work, four-quantum filter Maximum-Quantum NMR Spectroscopy (abbreviated as MAXY-CH), which was designed to selectively detect methyl groups, was chosen to directly monitor collective toxic substances in the extracts of herbs, focusing on characteristic methyl resonances that are toxicologically relevant. In such simplified NMR spectra, qualitative or semiquantitative analysis of the chemical transformation and detoxification process during the processing can be achieved readily. Additionally, quantitative analysis of toxic and active alkaloids in the processed herbs using MAXY-HSQC according to the limit value of Ch.P. 2020 was also validated. The study demonstrates the feasibility of monitoring collective toxic or active components in a holistic way during processing by MAXY experiments.