Study on the digestive and absorptive characteristics of Guizhi Decoction and its impact on drug efficacy using an in vitro intestinal culture model

Objective: To study the digestion pattern of Guizhi Decoction in various parts of the gastrointestinal tract and its efficacy based on an in vitro culture model of the intestinal tract. Methods: A rat in vitro intestinal culture model was established to simulate the digestive and absorptive processes of Guizhi Decoction in the stomach, duodenum, jejunum, ileum, cecum, and colon. High-performance liquid chromatography-mass spectrometry was used to analyze the absorption rates, permeability, and metabolic characteristics of its major components. Meanwhile, the anti-inflammatory effects of the digestion and absorption products in the exo-Taiwanese fluid of different intestinal segments were evaluated in conjunction with the LPS-induced inflammation model of RAW264.7 cells. Results: The major components of Guizhi Decoction were most effectively absorbed in the duodenum and jejunum and the colon, while the stomach and cecum showed lower absorption capacity. The permeability of cinnamic acid and liquiritigenin exceeded 100%, indicating partial conversion from other components through metabolic transformation. The cecum was identified as the primary site for the conversion of glycyrrhizic acid into glycyrrhetinic acid. The results of the pharmacodynamic experiments showed that the digestive absorption products could significantly reduce the NO concentration in the cellular supernatant under low-dose conditions, and showed good anti-inflammatory effects, especially the absorption products of the duodenum and jejunum segments had the strongest pharmacodynamic effects. Conclusions: The anti-inflammatory effect of Guizhi Decoction is mainly dependent on its digestion and absorption process in the gastrointestinal tract. The duodenum and jejunum are the main absorption sites for its pharmacologically active substances, the colon plays a significant role in reabsorption, and the cecum is crucial for metabolic transformation. This study provides a novel perspective for understanding the pharmacological basis and mechanisms of Guizhi Decoction.