Characterization of the chemical composition of different parts of Dolichos lablab L. and revelation of its anti-ulcerative colitis effects by modulating the gut microbiota and host metabolism

Ethnopharmacological relevance: Ulcerative colitis (UC) is a non-specific inflammatory disease characterized by long duration and easy relapse. Dolichos lablab L. (DLL) belongs to the family Fabaceae, was listed in a famous Chinese medical classic, Compendium of Materia Medic, and described as possessing features that invigorate the spleen, alleviate dampness, provide diarrhea relief, and other effects. The DLL-dried white mature seeds (DS) and dried flower (DF), which hold significant medicinal value in China, were used in clinical prescriptions to prevent and treat UC. DS and DF have appeared in different editions of the Pharmacopoeia of the People's Republic of China from 1977 to 2020. However, their chemical composition, pharmacological effects, and mechanism of treating UC are unclear. Aim of the study: This study aimed to characterize the chemical composition of different parts of DLL (seeds and flowers), further explore their pharmacological effects, and elaborate its underlying mechanism of treating UC. Methods: The chemical composition of DS and DF crude polysaccharides (DSP and DFP) and ethanolic extracts (DSE and DFE) were characterized by high-performance anion-exchange chromatography (HPAEC), ultra-high performance liquid chromatography-mass spectrometry (UHPLC-MS), and gas chromatography-mass spectrometry (GC-MS). Then, based on the acute UC mice model, the pharmacodynamic effects were investigated by Western blotting, ELISA, and other methods. Finally, the 16S rRNA gene sequencing and metabonomic analysis were used to explore the regulatory effects of DS and DF on intestinal microbiota and host metabolism. Results: DSE and DFE inhibited the oxidative stress response, reducing proinflammatory factor production and maintaining intestinal barrier integrity in UC mice. The 16S rRNA gene sequencing and metabonomic analysis revealed that DS and DF treated UC by regulating the intestinal microbiota structure and reversing the abnormal metabolism of the host. Conclusion: This study suggested that different parts of DLL (flowers and seeds) may be potential medicines for treating UC, which exert their therapeutic effects through various active ingredients and might contribute significantly to reducing the economic pressures and challenges of UC treatment worldwide.