[Metabolic pathway and metabolites of total diterpene acid isolated from Pseudolarix kaempferi].

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].

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.

Metabolic analysis of four phenolic acids in rat by liquid chromatography-tandem mass spectrometry.

A liquid chromatography-diode array detection-electrospray ionization ion trap mass spectrometry (LC-DAD-ESI-MS(n)) method was established for the analysis of danshensu, caffeic acid, ferulic acid and isoferulic acid in rat plasma, bile, urine and feces after oral administration or intravenous injection. Liquid-liquid extraction was employed for the preparation of biosamples, and the chromatographic separation was carried out using an Agilent Zorbax Extend C(18) reversed phase column and acetonitrile-0.1% formic acid as the mobile phase. Totally nineteen metabolites were detected and identified as prototype, methylated, hydroxylated, sulfated and glucuronized conjugates. The metabolism of the individual phenolic acids in biosamples was investigated, and the metabolic pathway was proposed. By comparing the metabolism of different compounds which shared similar structures, we were able to find that methylation was the main pathway of danshensu metabolism, and the double bond on the side chain was critical for the drug excretion via bile and the formation of glucuronized conjugates. The results proved that the established method was simple, sensitive and reliable, which could be used to detect and identify the structures of metabolites and to better understand their in vivo metabolism.

Determination of danshensu in rat plasma and tissues by high-performance liquid chromatography.

A systematic study on pharmacokinetics and tissue distribution of danshensu (one of the major active components from Salvia miltiorrhizae) is conducted using a rapid and sensitive high-performance liquid chromatographic (HPLC) method. Before HPLC analysis, biological samples are pretreated with a liquid-liquid extraction. Separation of danshensu and internal standard is achieved on an Agilent Zorbax C18 column with a mobile phase made up of acetonitrile and 0.05% trifluoracetic acid at a flow rate of 0.8 mL/min. The calibration curves in plasma and tissues are linear in the given concentration ranges, with r2 no less than 0.99. The intra-day and inter-day relative standard deviations in the measurement of quality control samples are less than 15%, and the accuracies are in the range of 86-115%. The recoveries of danshensu in plasma and tissues are among 80% to 118%. Meanwhile, the multi-peaks in pharmacokinetic profiles are observed. The method is successfully applied to the pharmacokinetics and tissue distribution study of danshensu after a single oral administration of 50.0 mg/kg sodium danshensu to rats.

Structural characterization of metabolites of salvianolic acid B from Salvia miltiorrhiza in normal and antibiotic-treated rats by liquid chromatography-mass spectrometry.

This study was conducted to compare the in vivo metabolites of salvianolic acid B (Sal B) between normal rats and antibiotic-treated rats and to clarify the role of intestinal bacteria on the absorption, metabolism and excretion of Sal B. A valid method using LC-MS(n) analysis was established for identification of rat biliary and fecal metabolites. And isolation of normal rat urinary metabolites by repeated column chromatography was applied in this study. Four biliary metabolites and five fecal metabolites in normal rats were identified on the basis of their MS(n) fragmentation patterns. Meanwhile, two normal rat urinary metabolites were firstly identified on the basis of their NMR and MS data. In contrast, no metabolites were detected in antibiotic-treated rat urine and bile, while the prototype of Sal B was found in antibiotic-treated rat feces. The differences of in vivo metabolites between normal rats and antibiotic-treated rats were proposed for the first time. Furthermore, it was indicated that the intestinal bacteria showed an important role on the absorption, metabolism and excretion of Sal B. This investigation provided scientific evidence to infer the active principles responsible for the pharmacological effects of Sal B.

Characterization of chemical constituents in Guan Xin II decoction by liquid chromatography coupled with electrospray ionization-mass spectrometry.

Guan Xin II decoction (GX II) is a widely used traditional Chinese medicine (TCM) formula for the treatment of coronary heart diseases. However, the comprehensive chemical analysis of the formulated GX II is not clarified yet. An HPLC-DAD-ESI-MSn method was established to analyze GX II and its five component herbs, respectively. A total of 57 compounds, including phenolic acids, glycosides, flavonoids, and alkaloids were identified or tentatively characterized on the basis of their mass spectra or by comparison with reference standards. This is the first time that the chemical composition of GX II was elucidated by LC/MS. The established method will be used for quality control and pharmacokinetic studies of GX II.