Determination of the antidiabetic chemical basis of Phellodendri Chinensis Cortex by integrating hepatic disposition in vivo and hepatic gluconeogenese inhibition in vitro

Ethnopharmacological relevance: Phellodendri Chinensis Cortex (PCC) has been an herb clinically used to treat diabetes, but the chemical basis of its antidiabetic effects has remained unclear. Aim of this study: Based on the efficacy of herbal medicine resulting from the cooperative response of the effective compounds in the target organs with sufficient exposure, the in vivo hepatic disposition and in vitro hepatic gluconeogenesis inhibition were integrated to elucidate the chemical basis for the antidiabetic effect of orally administered PCC from a target organ, liver, perspective. Materials and methods: With a developed and validated HPLC-MS/MS method, three alkaloids and five metabolites were determined in the portal vein plasma, liver, and systemic plasma of rats orally administered PCC. The inhibition of hepatic gluconeogenesis by the eight compounds was evaluated in primary hepatocytes. Results: The in vivo results showed that magnoflorine was present at the highest concentration among the target constituents in the plasma, where berberine showed a low concentration. In contrast, berberine showed the highest concentration in the liver, and its five metabolites exhibited substantial hepatic accumulation. This discrepancy was strongly associated with the hepatic disposition of the compounds. The hepatic disposition prevented the transfer of 96.1% of the phellodendrine, 71.1% of the berberine and 47.5% of the magnoflorine from the portal vein plasma to the systemic plasma, which corresponded to their hepatic distribution and hepatic metabolism. In vitro, berberine, M1, M4 and M5 significantly and dose-dependently inhibited hepatic glucose production. By integrating the hepatic exposure and inhibitory activity data, we estimated that berberine contributed the most (74%) to the total glucose production inhibition of the orally administered PCC decoction, followed by M4 (14%), M1 (11%) and M5 (1%). Conclusion: This study was the first to comprehensively describe the pharmacokinetic profiles and hepatic disposition of alkaloids in PCC, and concluded that berberine and its metabolites contributed the most to the total hepatic gluconeogenesis inhibition by orally administered PCC. These results reveal the chemical basis for the antidiabetic effect of orally administered PCC decoction, providing scientific evidence to support the clinical usage of PCC in diabetes treatment.