Gastrointestinal Absorption and Metabolic Dynamics of Jujuboside A, A Saponin Derived from the Seed of Ziziphus jujuba

Jujuboside A (JuA), an active saponin, is responsible for the anxiolytic and sedative effects of Zizyphi Spinosae Semen (ZSS). In this study, the gastrointestinal absorption and metabolic dynamics of JuA were investigated in vivo and in vitro. The results showed that the bioavailability was 1.32% in rats, indicating only a trace amount of JuA was able to be absorbed. Further investigation revealed that its poor bioavailability was not caused by malabsorption but by the metabolic process. JuA was hydrolyzed largely in the stomach before being absorbed into the different parts of the intestine (especially duodenum and colon), and the gastric environment played a vital role in this process. Furthermore, the metabolites, jujuboside B (JuB) and jujubogenin, exhibited significant effects on the expression and activation of γ-amino-butyric acid A (GABA(A)) receptors. Our findings demonstrate that the metabolites of the saponin, not the original molecule, should be responsible for the specific bioactivities.