Background: In China, Zhishi (Aurantii Fructus Immaturus) - Baizhu (Atractylodis Macrocephalae Rhizoma) is a well-known herb pair used to treat gastrointestinal motility disorders for thousands of years, and it has especially shown a definite advantage in the treatment of slow transit constipation (STC). However, the mechanism of Zhishi-Baizhu (ZSBZ) in the treatment of STC remains unclear. In this study, plasma metabolomics research combined with metabolic pathway analysis has been used to illuminate the potential mechanism of its effects against STC.

Methods: Parameters of intestinal transit ratio, plasma motilin (MTL), substance P (SP), adenosine triphosphate (ATP), histological alteration of the colon and MLCK expression in the colon were detected to evaluate the effects with respect to STC. Principal component analysis (PCA) was used to investigate the global metabolite alterations, while orthogonal partial least squares discriminant analysis (OPLS-DA) and t-test were used to filter potential metabolite markers. Moreover, metabolic pathway analysis was employed.

Results: Oral administration of ZSBZ significantly prevented the development of STC. It increased the expression of MTL and SP in serum, as well as the expression of ATP and MLCK in the colon. ZSBZ administration alleviated symptoms in loperamide-induced constipated rats, evidenced by the increase of intestinal transit ratio. Futhermore, 9 potential biomarkers of STC were screened, and the levels were all reversed to different degrees after ZSBZ administration. Metabolic pathway analysis showed that the improvement of STC by ZSBZ was mainly related to caffeine and vitamin B6 metabolism.

Conclusions: Our study identifies the metabolic networks of constipated rats and demonstrates the efficacy of this metabolomics approach to systematically study the therapeutic effects of ZSBZ on constipation.

Keywords: Atractylodis Macrocephalae Rhizoma; Aurantii Fructus Immaturus; herb pair; slow transit constipation (STC).