Metabolic pathway and metabolites of total diterpene acid isolated from Pseudolarix kaempferi / 药学学报

The preliminary metabolic profile of total diterpene acid (TDA) isolated from Pseudolarix kaempferi was investigated by using in vivo and in vitro tests. Pseudolaric acid C2 (PC2) was identified as the predominant metabolite in plasma, urine, bile and feces after both oral and intravenous administrations to rats using HPLC-UV and HPLC-ESI/MS(n), and demethoxydeacetoxypseudolaric acid B (DDPB), a metabolite proposed to be the glucoside of PC2 (PC2G), as well as pseudolaric acid C (PC), pseudolaric acid A (PA), pseudolaric acid A O-beta-D glucopyranoside (PAG), pseudolaric acid B O-beta-D glucopyranoside (PBG) and deacetylpseudolaric acid A (DPA) originated from TDA could also be detected. It was demonstrated by tests that the metabolism of TDA is independent of intestinal microflora, and neither of pepsin and trypsin is in charge of metabolism of TDA, TDA is also stable in both pH environments of gastric tract and intestinal tract. The metabolites of TDA in whole blood in vitro incubation were found to be PC2, DDPB and PC2G, which demonstrated that the metabolic reaction of TDA in vivo is mainly occurred in blood and contributed to be the hydrolysis of plasma esterase to ester bond, as well as the glucosylation reaction. These results clarified the metabolic pathway of TDA for the first time, which is of great significance to the in vivo active form and acting mechanism research of P. kaempferi.

Metabolic pathway and metabolites of pseudolaric acid B / 药学学报

The metabolic profile of pseudolaric acid B (PB) was investigated by using in vivo and in vitro tests. Pseudolaric acid C2 (PC2) was identified as the specific metabolite of PB in plasma, urine, bile and feces using HPLC and HPLC-ESI/MS(n) after both oral and intravenous administration to rats, and almost no prototype was detected in all kinds of samples. The metabolic behaviors of PB orally administered in rats treated with antibiotics to eliminate intestinal microflora were identical with those in untreated rats, demonstrating that the metabolism of PB is independent of intestinal microflora. PB was stable in 48 h respective incubation with artificial gastric juice and artificial intestinal juice, suggesting that neither pepsin nor trypsin is in charge of metabolism of PB, and also demonstrating that PB is stable in both pH environments of gastric tract and intestinal tract. In vitro research on metabolism of PB in rat liver microsomes incubation revealed that little PB was metabolized and that the proposed metabolites were the demethoxy and demethoxydecarboxy products of the prototype. The amount of metabolites was extremely low compared with the prototype, indicating that liver microsomes are not responsible for the metabolism of PB either. PB was gradually metabolized into PC2 during 1 h in whole blood incubation in vitro, and the metabolic process showed dynamically dependent manner with incubation time. Once absorbed into blood, PB was quickly metabolized into PC2, accordingly, little prototype was detected in all kinds of samples. The metabolism was attributed to the rapid hydrolysis of C-19 ester bond by plasma esterase. These results clarified the metabolic pathway of PB for the first time, which was of great significance to identify the in vivo active form and interpret acting mechanism of the active compounds of P. kaempferi.