Opposite Effects of Single-Dose and Multidose Administration of the Ethanol Extract of Danshen on CYP3A in Healthy Volunteers.

The aim of this study was to investigate the effect of single- and multidose administration of the ethanol extract of danshen on in vivo CYP3A activity in healthy volunteers. A sequential, open-label, and three-period pharmacokinetic interaction study design was used based on 12 healthy male individuals. The plasma concentrations of midazolam and its metabolite 1-hydroxymidazolam were measured. Treatment with single dose of the extract caused the mean C max of midazolam to increase by 87% compared with control. After 10 days of the danshen extract intake, the mean AUC0-12, C max, and t 1/2 of midazolam were decreased by 79.9%, 66.6%, and 43.8%, respectively. The mean clearance of midazolam was increased by 501.6% compared with control. The in vitro study showed that dihydrotanshinone I in the extract could inhibit CYP3A, while tanshinone IIA and cryptotanshinone could induce CYP3A. In conclusion, a single-dose administration of the danshen extract can inhibit intestinal CYP3A, but multidose administration can induce intestinal and hepatic CYP3A.

Inhibitory effects of gypenosides on seven human cytochrome P450 enzymes in vitro.

Among the various possible causes for drug interactions, pharmacokinetic factors such as inhibition of drug-metabolizing enzymes, especially cytochrome P450 (CYP) enzymes, are regarded as the most frequent and clinically important. Gypenosides is widely used as functional food and over-the-counter drug in East Asia. In this study, the in vitro inhibitory effects of gypenosides on the major human CYP enzymes (CYP1A2, CYP2B6, CYP2C8, CYP2C9, CYP2C19, CYP2D6, and CYP3A4) activities in human liver microsomes were examined using liquid chromatography-tandem mass spectrometry. Gypenosides showed the strongest inhibition of CYP2D6, followed by CYP2C8, CYP3A4 and CYP2C9. The IC50 values were 1.61 µg/mL, 20.06 µg/mL, 34.76 µg/mL (CYP3A4/midazolam), 46.73 µg/mL (CYP3A4/testosterone), and 54.52 µg/mL, respectively. Gypenosides exhibited competitive inhibition of CYP2D6 (Ki=1.18). In conclusion, Gypenosides might cause herb-drug interactions via inhibition of CYP2D6. An in vivo study is needed to examine this further.

Pharmacokinetic study of multiple active constituents after oral gavage of Guizhi decoction in rats using a LC-MS/MS method.

Guizhi decoction (GZD) is a classic traditional Chinese medicine formula, clinically used for the treatment of influenza, common cold, and other pyretic conditions. A sensitive, specific, and validated liquid chromatography-tandem mass spectrometric (LC-MS/MS) method was developed to investigate the pharmacokinetic properties of cinnamic acid, hippuric acid, paeoniflorin, and glycyrrhetic acid in rat. After single dose oral administration of 7.9 g extract/kg body weight GZD in rats, plasma concentrations of cinnamic acid, hippuric acid, paeoniflorin, and glycyrrhetic acid were measured by LC-MS/MS. Pharmacokinetic parameters were calculated from the plasma concentration-time data. The values of AUC0-t, half-life (t 1/2), and C max were 7.2 ± 2.3 µg h/mL, 1.2 ± 0.3 h, and 9.2 ± 5.2 µg/mL for cinnamic acid, 53 ± 31 µg h/mL, 2.8 ± 2.0 h, and 17 ± 3 µg/mL for hippuric acid, 1.1 ± 0.5 µg h/mL, 1.9 ± 1.1 h, and 0.6 ± 0.3 µg/mL for paeoniflorin, and 11 ± 6 µg h/mL, 6.6 ± 2.5 h, and 0.9 ± 0.6 µg/mL for glycyrrhetic acid, respectively. The results would offer useful information for effective components of GZD in vivo.

Increased systemic exposure to rhizoma coptidis alkaloids in lipopolysaccharide-pretreated rats attributable to enhanced intestinal absorption.

Rhizoma coptidis is a rhizome commonly used in traditional Chinese medicine. After oral administration of rhizoma coptidis extract, the plasma concentrations of its effective alkaloid constituents are so low that their systemic therapeutic actions cannot be explained. This study aimed to investigate the influence of lipopolysaccharide (LPS) on the pharmacokinetics of the rhizoma coptidis alkaloids. Pharmacokinetic experiments were performed with rats; both in vitro absorption and efflux experiments were carried out with everted rat gut sacs, whereas in vitro metabolism experiments were conducted with rat liver microsomes and intestinal S9 fractions. Mucosal changes were evaluated with light microscopy and transmission electron microscopy. The results showed that, in rat plasma, LPS pretreatment increased systemic alkaloid exposure. LPS pretreatment increased the in vitro absorption of the alkaloids and decreased their efflux. The efflux of vinblastine and rhodamine 123, P-glycoprotein substrates, also was decreased. The absorption of fluorescein isothiocyanate-labeled dextran (average molecular mass, 4 kDa), a gut paracellular permeability probe, was not influenced. Obvious damage was observed in the mucosa, but the tight junctions between epithelial cells remained intact. Intestinal, rather than hepatic, alkaloid metabolism was decreased. These findings indicated that LPS pretreatment increased systemic exposure to the alkaloids through enhancement of their absorption, which was related to decreased intestinal efflux and metabolism. The results add to the understanding of why rhizoma coptidis is active despite the low plasma concentrations of the rhizoma coptidis alkaloids measured in normal subjects and experimental animals.

Lipopolysaccharide increased the acute toxicity of the Rhizoma coptidis extract in mice by increasing the systemic exposure to Rhizoma coptidis alkaloids.

ETHNOPHARMACOLOGICAL RELEVANCE: Rhizoma coptidis is used as an antidysenteric in clinics in China. However, patients suffering from dysentery are susceptible to the acute toxicity of Rhizoma coptidis. The current study investigates the effects of lipopolysaccharide (LPS), which are a key pathogenic factor in dysentery, on the acute toxicity of a Rhizoma coptidis extract in mice; possible mechanisms are proposed. MATERIALS AND METHODS: Acute toxicity and pharmacokinetic experiments in mice were conducted. The plasma concentration of Rhizoma coptidis alkaloids in mice was determined using liquid chromatography/tandem mass spectrometry. The activity of acetylcholinesterase (AChE) in the tissue homogenate was determined using an AChE determination kit. RESULTS: Pretreatment with LPS for 16 h increased the acute toxicity of the oral Rhizoma coptidis extract. Systemic exposure to Rhizoma coptidis alkaloids was also increased by LPS pretreatment. Neostigmine significantly increased whereas pyraloxime methylchloride reduced the acute toxicity of the Rhizoma coptidis extract. LPS pretreatment alone showed no significant effect on the activity of thoracoabdominal diaphragm AChE. However, it enhanced the inhibitory effect of the Rhizoma coptidis extract. LPS pretreatment did not affect the acute toxicity of various dosages of tail vein-injected berberine. CONCLUSIONS: LPS increased the acute toxicity of the oral Rhizoma coptidis extract in mice by increasing the systemic exposure to the Rhizoma coptidis alkaloids.

Intestinal absorption mechanisms of berberine, palmatine, jateorhizine, and coptisine: involvement of P-glycoprotein.

The absorption and transport mechanisms of berberine, palmatine, jateorhizine, and coptisine were studied using a Caco-2 cells uptake and transport model, with the addition of cyclosporin A and verapamil as P-glycoprotein (P-gp) inhibitors and MK-571 as a multidrug resistance-associated protein 2 (MRP(2)) inhibitor. In the uptake experiment, berberine, palmatine, jateorhizine, and coptisine were all taken into Caco-2 cells, and their uptakes were increased in the presence of cyclosporin A or verapamil. In the transport experiment, P(app) (AP-BL) was between 0.1 and 1.0 × 10(6) cm/sec for berberine, palmatine, jateorhizine, and coptisine and was lower than P(app) (BL-AB). ER values were all >2. Cyclosporin A and verapamil both increased P(app) (AP-BL) but decreased P(app) (BL-AB) for berberine, palmatine, jateorhizine, and coptisine; ER values were decreased by >50%. MK-571 had no influence on the transmembrane transport of berberine, palmatine, jateorhizine, and coptisine. At a concentration of 1-100 µM, berberine, palmatine, jateorhizine, and coptisine had no significant effects on the bidirection transport of Rho123. Berberine, palmatine, jateorhizine, and coptisine were all P-gp substrates; and at the range of 1-100 µM, berberine, palmatine, jateorhizine, and coptisine had no inhibitory effects on P-gp.