Inhibitory effects of Coptidis Rhizoma on the intestinal absorption and metabolism of Scutellariae Radix.

ETHNOPHARMACOLOGICAL RELEVANCE: The Scutellariae Radix (SR) and Coptidis Rhizoma (CR) herb couple is widely used in traditional Chinese medicine prescriptions for the treatment of diabetes mellitus due to its interaction and synergistic effect compared to either herb alone, but the underlying mechanism of interaction between these herbs is unclear. This study aimed to investigate the effects of CR on the metabolism and absorption of SR. MATERIALS AND METHODS: After rats were treated with normal saline (NS group) or the CR extract (CR-treated group) for seven consecutive days, the intestinal flora was extracted from rat faeces for a co-incubation with the SR extract to investigate the metabolism of SR flavonoids, and a non-everted gut sac was prepared in vitro to evaluate the intestinal absorption of the SR extract. The components of the SR extract, the metabolites of the SR extract that was co-incubated with intestinal flora, and the dialysate acquired from non-everted gut sacs were identified and determined by an HPLC-MS/MS method. The absorption rate constant (Ka) and the apparent permeability (Papp) of each compound were calculated, and the effects of CR on the metabolism and absorption of flavonoids in SR were evaluated, by comparison the Ka and Papp between two groups using Student's t-test. RESULTS: Twenty-nine flavonoids were detected and identified in the SR extract, including 16 glycosides and 13 aglycones. In the co-incubation with the intestinal flora, differences in metabolite classes were not observed between the NS group and CR-treated group; however, the metabolic rates of 17 flavonoids in the CR-treated group were significantly higher than the NS group. The Papp of 11 compounds (4 glycosides and 7 aglycones) across the gut sac were greater than 2 × 10-5 cm/s in both groups, while the Papp values of 7 compounds including wogonoside (WG) and other aglycones were significantly decreased in the CR-treated group. CONCLUSION: Based on these results, CR decreased the metabolism and absorption of SR flavonoids, and exerted much greater inhibitory effects on aglycones than glycosides, which may be one of the potential mechanisms underlying the therapeutic effects of the combination of SR and CR on diabetes mellitus.

In vitro and in vivo identification of metabolites of magnoflorine by LC LTQ-Orbitrap MS and its potential pharmacokinetic interaction in Coptidis Rhizoma decoction in rat.

Magnoflorine, an important aporphine alkaloid in Coptidis Rhizoma, is increasingly attracting research attention because of its pharmacological activities. The in vivo and in vitro metabolism of magnoflorine was investigated by LC LTQ-Orbitrap MS. In vivo samples including rat urine, feces, plasma and bile were collected separately after both oral (50 mg kg(-1) ) and intravenous administration (10 mg kg(-1) ) of magnoflorine, along with in vitro samples prepared by incubating magnoflorine with rat intestinal flora and liver microsome. As a result, 12 metabolites were found in biological samples. Phase I metabolites were identified in all biological samples, while phase II metabolites were mainly detected in urine, plasma and bile. In a pharmacokinetic study, rats were not only dosed with magnoflorine via oral (15, 30 and 60 mg kg(-1) ) and intravenous administration (10 mg kg(-1) ) but also dosed with Coptidis Rhizoma decoction (equivalent to 30 mg kg(-1) of magnoflorine) by intragastric administration to investigate the interaction of magnoflorine with the rest of compounds in Coptidis Rhizoma. Studies showed that magnoflorine possessed lower bioavailability and faster absorption and elimination. However, pharmacokinetic parameters altered significantly (p < 0.05) when magnoflorine was administered in Coptidis Rhizoma decoction. Oral gavage of Coptidis Rhizoma decoction decreased the absorption and elimination rates of magnoflorine, which revealed that there existed pharmacokinetic interactions between magnoflorine and the rest of ingredients in Coptidis Rhizoma.

[Identification of metabolites of epiberberine in rat liver microsomes and its inhibiting effects on CYP2D6].

Epiberberine, one of the most important isoquinoline alkaloid in Coptidis Rhizoma, possesses extensive pharmacological activities. In this paper, the liquid chromatography-tandem mass spectrometry (LC-MS/MS) was used to study phase I and phase II metabolites. A Thermo HPLC system (including Surveyor AS, Surveyor LC Pump, Surveyor PDA. USA) was used. The cocktail probe drugs method was imposed to determine the content change of metoprolol, dapsone, phenacetin, chlorzoxazone and tolbutamide simultaneously for evaluating the activity of CYP2D6, CYP3A4, CYP1A2, CYP2E1 and CYP2C9 under different concentrations of epiberberine in rat liver microsomes. The result showed that epiberberine may have phase I and phase II metabolism in the rat liver and two metabolites in phase I and three metabolites in phase II are identified in the temperature incubation system of in vitro liver microsomes. Epiberberine showed significant inhibition on CYP2D6 with IC50 value of 35.22 µmol L(-1), but had no obvious inhibiting effect on the activities of CYP3A4, CYP1A2, CYP2E1 and CYP2C9. The results indicated that epiberberine may be caused drug interactions based on CYP2D6 enzyme. This study aims to provide a reliable experimental basis for its further research and development of epiberberine.

[Stability study in biological samples and metabolites analysis of astragaloside IV in rat intestinal bacteria in vitro].

To figure out the stability and intestinal bacteria metabolites of rats in vitro of astragaloside IV ( AST), this research was done to explore the stability of AST in the artificial gastric juice. artificial intestinal juice and rat liver homogenate and the metabolism in rat intestinal in vitro. HPLC was used to calculate the remaining rate of AST in biological samples by measuring the content of AST, while metabolites were determined by combining the methods of TLC, HPLC and LC-MS/MS. It turned out that AST was difficult to metabolize in the artificial gastric juice, artificial intestinal juice and rat liver. Also, the metabolic pathway of AST was stepped by deglycosylation. Firstly, AST was converted to its secondary etabolites (6-O-ß-D-glucopyranosyl- cycloastragenol, CMG) by removal of xylose moiety at C-3, then transformed into cycloastragenol (CAG) after hydrolytic removal of the glucose moiety at C-6. All the results suggested that the metabolism of AST in vivo occurs mainly in the intestinal by hydrolysis of glycosyl. In conclusion, hydrolysis of intestinal flora is the main reason that AST metabolizes.

[Effect of comparability of Coptis chinensis and Scutellaria baicalensis on five sub-enzymatic activities of liver microsomes in rats].

To study the mechanism of metabolic interaction between Coptis chinensis and Scutellaria baicalensis. Rats were given C. chinensis and S. baicalensis for 7 days to produce hepatic microsomal enzyme. Cocktail probe substrate and liver microsome in vitro temperature incubation method were adopted. Meanwhile, the metabolic elimination percentages of the five probe substrates were detected with HPLC, in order to evaluate the effect of each administration group on the enzymatic activity of rat liver microsome CYP450. Compared with the blank group, C. chinensis obviously inhibited CYP2D6 and CYP1A2, and S. baicalensis remarkably inhibited CYP1A2, CYP2E1 and CYP2C9. The compatibility of C. chinensis and S. baicalensis with the ratio of 1:1 not only inhibited CYP1A2, but also remarkably activated CYP2D6 and CYP3A4. However, their activation effect disappeared under the ratio of 2: 1, and turned into the inhibitory effect on CYP1A2 and CYP2C9. The results showed that C. chinensis and S. baicalensis had an inhibitory effect on CYP450, but their compatibility with certain ratio resulted in double effects of activation and inhibition, which was related to their compatibility ratio. It is speculated that the inhibitory and inducing effects of C. chinensis and S. baicalensis on metabolic enzymes are among causes for their attenuation and synergistic effects.