Objective To investigate the dynamic changes of volatile and water-soluble constituents in Schizonepetae Herba and Cinnamomi Cortex decoctions at different boiling durations, reveal the characteristics of constituent dissolution, volatilization, and degradation during decoction from the material basis, and provide a scientific basis for rational determination of decoction time and different administration routes (e.g., decoction, powder infusion) in clinical practice. Methods Decoctions of JIngjie (Schizonepetae Herba) and Rougui (Cinnamomi Cortex) were prepared at different boiling times. A headspace GC-MS/MS method was established and validated for pulegone, menthone, o-methoxycinnamaldehyde, and cinnamaldehyde, and their content changes at different decoction times were compared. UPLC-Q-TOF MS/MS was employed to characterize and semi-quantify water-soluble constituents. Normalized ion intensities and clustering analysis were used to assess the impact of boiling duration on the overall chemical profile. Results The four volatile compounds exhibited distinct time-dependent patterns.Pulegone, menthone, and cinnamaldehyde increased rapidly at early stages and declined thereafter, whereas o-methoxycinnamaldehyde increased continuously. A total of 139 water-soluble constituents were identified by UPLC‑Q‑TOF MS/MS, many of which showed reduced abundance with prolonged boiling, indicating potential heat degradation. Integrated analysis suggested that approximately 7.5 min represents an optimal decoction time for Schizonepetae Herba. For Cinnamomi Cortex, prolonged decoction is not suitable when emphasizing the effects of warming yang and reinforcing fire, whereas appropriate prolonged decoction or alternative administration such as powder infusion can be used when emphasizing warming and unblocking to relieve pain. Conclusion Schizonepetae Herba and Cinnamomi Cortex exhibit clear time-dependent chemical changes during decoction. Boiling time critically influences the retention of volatile and water-soluble constituents. The results provide a reference for selecting decoction time and optimizing administration routes of the two herbs under different clinical applications, and offer an experimental basis for the standardization and modernization of traditional Chinese medicine decoctions.

Schizonepetae Herba  /  Cinnamomi Cortex  /  decoction time  /  volatile compounds  /  water-soluble compounds  /  dynamic component changes  /  menthone  /  pulegone  /  o-methoxycinnamaldehyde  /  cinnamaldehyde