An Integrative Strategy Combining In-House Database-Driven UHPLC-QTOF-MS/MS Analysis, Multivariate Statistics, and Simulated Acidic Decoction Experiments to Profile Constituent Variations and Transformations in the Maidong-Wuweizi Herb Pair.

The Maidong-Wuweizi (MW) herb pair is a classic traditional Chinese medicine (TCM) combination known for synergistically nourishing yin and replenishing qi, and is widely used in more than 40 preparations. In this study, an integrated analytical strategy was established to systematically investigate the dynamic chemical evolution and underlying transformation pathways of MW during co-decoction. A comprehensive in-house chemical database was constructed. Ultra-high-performance liquid chromatography coupled with quadrupole time-of-flight mass spectrometry and multivariate statistical analysis (MVA) was used to compare the chemical profiles of MW co-decoction with those of the respective single decoctions. A total of 102 compounds from Maidong (MD) and 86 compounds from Wuweizi (WWZ) were characterized. Notably, 14 compounds were detected exclusively in the co-decoction and were putatively annotated as transformation products of steroidal saponins originating from MD. Furthermore, MVA enabled the precise identification of differential markers reflecting the combinatorial interactions within the MW herb pair. Compared with the respective single decoctions, the co-decoction exhibited significant changes in the relative abundances of seven WWZ-derived compounds (one amide, one phenolic constituent, and five lignans) and 21 MD-derived markers, mainly comprising bicyclic monoterpenoid glycosides, steroidal saponins, homoisoflavonoids, and fatty acids. Validation of the chemical transformation patterns using simulated decoction experiments demonstrated that the acidic environment induced by WWZ, combined with the thermal treatment during decoction, promoted the deglycosylation of bicyclic monoterpenoid diglycosides and the dehydration and deglycosylation of specific steroidal saponins. Meanwhile, this acidic environment reduced the apparent solubility of homoisoflavonoids. In sum, this study employed a database-driven identification approach, multivariate statistical screening, and simulated transformation validation to systematically characterize the dynamic chemical profiles and key transformation pathways of the MW herb pair. These findings provide a scientific basis for elucidating the material basis of MW and a valuable methodological framework for investigating complex TCM formulas.