Quasi-targeted metabolomics analysis reveals linkage between chemical composition and different post-harvest processing methods of <i>Polygala tenuifolia</i>

The dried root bark of <italic>Polygala tenuifolia</italic> is widely recognized in traditional Chinese medicine (TCM) for its role in promoting cerebral tranquility. However, conventional post-harvest processing methods present challenges in maintaining consistent quality, prompting increased interest in developing improved processing techniques. This study systematically evaluates the impact of three common post-harvest processing methods on the quality of <italic>P. tenuifolia</italic>. Concentrations of three key bioactive components, tenuifolin (TF), 3,6-disinapoyl sucrose, and polygalaxanthone III, designated as quality markers in the Chinese Pharmacopoeia (2020), were used as analytical indicators. Correlation analysis indicated that separating phloem and xylem water content did not significantly affect the levels of these active compounds in the final product. However, both rehydration and prolonged storage of fresh roots compromised quality: rehydration accelerated the degradation of 3,6-disinapoyl sucrose, while extended storage led to a reduction in TF content. Quasi-targeted metabolomics further revealed significant processing-dependent shifts in the metabolic profile. Fresh-cut samples were enriched in neuroactive primary metabolites such as L-theanine and <italic>γ</italic>-aminobutyric acid, suggesting a pharmacological basis for the herb's tranquilizing effects. Additionally, the three processing methods differentially affected the biosynthesis of phenylpropanoid compounds: upstream intermediates accumulated in fresh-stored samples, whereas downstream metabolites were more prevalent in samples processed by the other two methods. In conclusion, this study provides a comprehensive comparison of three post-harvest techniques, highlights the advantages of fresh-cut <italic>P. tenuifolia</italic>, and offers valuable insights for optimizing quality control (QC) and therapeutic efficacy in future research.