Qualitative and Quantitative Characterization of Isodon rubescens and Its Pharmaceutical Preparations Using NMR and UHPLC‐QTOF‐MS

Isodon rubescens is a widely used traditional folk medicine in China. In this study, 13 natural products were isolated using a two-step ethanol extraction. Notably, flavonoid glycosides 2 and 4, and polymeric caffeic acids 7 and 8, were identified for the first time from the secondary extraction residues, highlighting the continued presence of bioactive compounds with potential for further development. Oridonin (9), the major active compound, was quantified in nine commercial preparations using quantitative NMR (qNMR). Its concentration in the drop pill (0.92 mg/g) was comparable to that in the raw extract (0.90 mg/g). The three tablet samples showed varying levels: Tablet 3 (2.66 mg/g) > Tablet 1 (1.22 mg/g) > Tablet 2 (1.09 mg/g). Capsule, tea bag, and syrup samples could not be quantified due to low concentrations.