Metabolism of paeoniflorin and related compounds by human intestinal bacteria

Gaultherin, a natural salicylate derivative from Gaultheria yunnanensis: Towards a better non-steroidal anti-inflammatory drug

One of the major factors limiting the use of non-steroidal anti-inflammatory drugs is gastrointestinal toxicity. Gaultherin, 2-[(6-O-beta-D-Xylopyranosyl-beta-D-glucopyranosyl)oxy] benzoic acid methyl ester, a natural salicylate derivative extracted from Gaultheria yunnanensis, has been shown to have analgesic and anti-inflammatory effects and lack gastric ulcerogenic effect compared to aspirin in our primary study. The aim of this study was to investigate the mechanism of action of gaultherin, which may rely on its active metabolite, and the mechanism responsible for the non-ulcerogenic property. The results showed that gaultherin (200 mg/kg) significantly inhibited the abdominal contractions in the acetic acid-induced writhing test in mice. The anti-inflammatory effect of gaultherin was demonstrated in the croton oil-induced ear edema model in mice. The results showed that gaultherin and equimolar dose of aspirin produced comparable inhibitory effects. The study of the metabolism characters of gaultherin in mice and rats indicated that gaultherin could be metabolically converted to salicylate, which produced the pharmacological effects, and provided effective concentrations for an extended period. In vitro metabolism experiment showed that gaultherin was metabolized by beta-glycosidase produced by human intestinal bacteria and esterases in intestine, blood and liver successively to release salicylate finally. The study suggested gaultherin did not cause gastric ulcer for the reason that it released salicylate in intestine slowly, not in stomach and it left the cyclooxygenase-1 unaffected, which was the source of cytoprotective prostaglandins in gastric epithelium.

Inhibitory lignans against NFAT transcription factor from Acanthopanax koreanum

Three lignans isolated from the roots of A. koreanum (Araliaceae), namely eleutheroside E (1), tortoside A (2), and hemiariensin (4), were evaluated for their ability to inhibit NFAT transcription factor. Of these compounds, compound 4, possessing a diarylbutane skeleton, exhibited potent inhibitory activity against NFAT transcription factor (IC50: 36.3 +/- 2.5 microM). However, the activities of 1 (IC50: > 500 microM) and 2 (IC50: 136.1 +/- 9.4 microM), which possess bisaryldioxabicyclooctane skeletons, were lower. As the lignan derivatives of the same skeletons, hinokinin (5) and (-)-yatein (6) with diarylbutane skeletons and (+)-syringaresinol (3) with a bisaryldioxabicyclooctane skeleton were also studied for their inhibitory effects on NFAT transcription factor.

Ginsenoside Rh2 reduces ischemic brain injury in rats

Ginseng was incubated under mildly acidic conditions and its inhibitory effect on a rat ischemia-reperfusion model was investigated. When ginseng was treated with 0.1% hydrochloric acid at 60 degrees C, its protopanaxadiol saponins were transformed to diasteromeric ginsenoside Rg3 and Delta20-ginsenoside Rg3. When the transformed ginseng extract, of which the main component was ginsenosides Rg3, was treated with human intestinal microflora, the main metabolite was ginsenoside Rh2. Orally administered acid-treated ginseng (AG) extract and ginsenoside Rh2 potently protect ischemia-reperfusion brain injury. The ginsenoside Rh2 also inhibited prostaglandin-E2 synthesis in lipopolysaccharide-stimulated RAW264.7 cells, but showed no in vitro antioxidant activity. These results suggest that AG and ginsenoside Rh2 can improve ischemic brain injury.

Pharmacokinetic Interaction of Paeoniflorin and Sinomenine: Pharmacokinetic Parameters and Tissue Distribution Characteristics in Rats and Protein Binding Ability In Vitro

The root of Paeonia lactiflora and the stem of Sinomenium acutum are two herbs widely used in Chinese herbal medicine for the treatment of inflammatory and arthritic diseases. Studies on the interaction of the active constituents of these herbs, i.e., paeoniflorin and sinomenine, in pharmacokinetic parameters, tissues distribution, and protein binding ability could provide empirical data to support their clinical application. Following oral administration to rats, the pharmacokinetic alterations were compared. The results showed that the pharmacokinetic parameters (Cmax, Tmax, AUC, MRT, C(L), and Vd) of paeoniflorin were markedly enhanced when co-administrated with sinomenine. At 45 min after oral administration, the concentrations of paeoniflorin in the main internal organs were significantly increased when co-administrated with sinomenine. These phenomena were not ascribable to the alteration of the protein binding ability of paeoniflorin by sinomenine because obvious interactions of paeoniflorin and sinomenine in protein binding abilities in vitro to rat and rabbit plasma, human albumin, and alpha-1-acid-glycoprotein were not observed. However, with respect to the in vivo influence of paeoniflorin on sinomenine, the results showed that co-administration of paeoniflorin did not affect the pharmacokinetic parameters and tissue distribution of sinomenine.

Chinese medicine induces neurite outgrowth in PC12 mutant cells incapable of differentiation

During continuous culture of neural PC12 cells, we obtained a drug-hypersensitive PC12 mutant cell that showed high stimulation of neurite outgrowth by various drugs. When several Chinese medicines such as shu-jing-huo-xie-tang and Wu-Ling-San were provided to these PC12 mutant cells, the frequency of nerve growth factor (NGF)-induced neurite outgrowth increased approximately 30-fold compared to NGF alone. Neurite outgrowth induced by NGF in PC12 cells is accompanied by sustained activation of mitogen-activated protein kinase (MAPK); however, these Chinese medicines did not induce MAPK activity. The findings thus indicate that certain Chinese medicines may induce neurite outgrowth by a novel mechanism which is distinct from the NGF-activated pathway in PC12 mutant cells.

Protective Effects of Kakkalide From Flos Puerariae on Ethanol-Induced Lethality and Hepatic Injury Are Dependent on Its Biotransformation by Human Intestinal Microflora

When kakkalide, which was isolated from Flos Puerariae, was incubated with human fecal bacteria, kakkalide was metabolized to irisolidone via kakkalidone. When kakkalide (250 mg/kg) was orally administered to rats, irisolidone, but not kakkalide, was detected in the blood. The mortality associated with ethanol treatment was slightly reduced when the mice were intraperitoneally treated with kakkalide. Intraperitoneally administered kakkalide and kakkalidone did not reduce alcohol toxicity. However, orally administered kakkalide and intraperitoneally administered irisolidone significantly reduced the mortality. Orally administered kakkalide and intraperitoneally injected irisolidone greatly reduced serum alanine aminotransferase and aspartate aminotransferase activities in ethanol-intoxified mice. Orally administered kakkalide and intraperitoneally administered irisolidone significantly lowered the level of blood ethanol. The results indicate that kakkalide is a prodrug of irisolidone in protecting against ethanol-induced lethality and hepatic injury.

Development of a simple HPLC method for determination of paeoniflorin-metabolizing activity of intestinal bacteria in rat feces

A simple and reproducible HPLC method for the determination of paeoniflorin (PF)-metabolizing activity of intestinal bacteria in rat feces was developed and validated. Orally administered PF, a major active constituent of Paeoniae Radix, is metabolized into a bioactive compound, paeonimetabolin I (PM-I) by intestinal bacteria. Direct determination of the PF-metabolizing rate into PM-I is hard to achieve by HPLC due to the lack of intense chromophore in PM-I. However, when PF was incubated with Lactobacillus brevis, an intestinal bacterium, in the presence of phenylmercaptan, the metabolizing rate of PF into 8-phenylthio-paeonimetabolin I (PT-PM-I) was found to be equivalent to that of PF into PM-I. Thus, the PF-metabolizing activity of intestinal bacteria in rat feces was determined by measuring the rate of biotransformation of PF into PT-PM-I, which was detected by HPLC at 255 nm. This method can be utilized in the biopharmaceutical study of traditional Chinese formulations containing Paeoniae Radix.

Cytotoxic and antimutagenic stilbenes from seeds of Paeonia lactiflora

Cytotoxic and antimutagenic effects of a novel cis-epsilon-viniferin and five known stilbenes, transresveratrol, trans-epsilon-viniferin, gnetin H, suffruticosols A and B, isolated from the seeds of Paeonia lactiflora Pall. (Paeoniaceae) were determined against five different cancer cell lines, and mutagenicity of N-methyl-N'-nitro-N-nitrosoguanidine (MNNG) in Salmonella typhimurium TA100, respectively. Six stilbenes showed cytotoxic activity in a dose-dependent manner, and especially did potent cytotoxic activity against C6 (mouse glioma) cancer cell with IC50 values ranging from 8.2 to 20.5 microg/ml. trans-Resveratrol showed significant cytotoxic activity against HepG2 (liver hepatoma) and HT-29 (colon) human cancer cell lines with IC50 values of 11.8 and 25.2 g/ml, respectively. In contrast, trans-epsilon-viniferin and cis--viniferin, and gnetin H exhibited marked cytotoxic activity against Hela (cervicse) and MCF-7 (breast) human cancer cell lines with IC50 values of 20.4, 21.5, and 12.9 microg/ml, respectively. However, suffruticosol A and B had less cytotoxic effect against all cancer cells except C6. Meanwhile, six stilbenes exerted antimutagenic activity in a dose-dependent fashion. Of them, trans-resveratrol exhibited the strongest antimutagenic effect against MNNG with IC50 value of 27.0 microg/plate, while other five resveratrol oligomers also did moderate antimutagenic activity with IC50 values ranging from 31.7 to 35.2 microg/plate.

Stimulatory effect of paeoniflorin on the release of noradrenaline from ileal synaptosomes of guinea-pig in-vitro

The effect of paeoniflorin (an active principle of Paeoniae Radix, commonly used in traditional Chinese medicine) on the release of noradrenaline (norepineprhine) from nerve terminals was investigated using guinea-pig isolated ileal synaptosomes. Release was determined as the amount of noradrenaline, quantified by high-performance liquid chromatography-electrochemical detection, from samples incubated with paeoniflorin or vehicle. Paeoniflorin stimulated the release of noradrenaline in a concentration-dependent manner without an effect on the level of lactate dehydrogenase in the bathing medium. Tetrodotoxin abolished the action of paeoniflorin at concentrations sufficient to block sodium channels. The depolarizing effect of paeoniflorin on the membrane potential was also illustrated by a concentration-dependent increase in the fluorescence of bisoxonol. Moreover, the effect of paeoniflorin on bisoxonol fluorescence in ileal synaptosomes seems more potent than that of 4-aminopyridine. That paeoniflorin causes influx of calcium ions via the depolarization of nerve terminals could be considered. The noradrenaline-releasing action of paeoniflorin was abolished by removal of calcium chloride from the bathing medium. This action of paeoniflorin was also attenuated by Rp-cAMP atconcentrations sufficientto inhibitthe action of cyclicAMP. Therefore, paeoniflorin could induce a calcium-dependent and cyclic-AMP-related release of noradrenaline from sympathetic nerve terminals of guinea-pig ileum. Guanethidine inhibited the noradrenaline-releasing action of paeoniflorin in a concentration-dependent manner. The effect of paeoniflorin on the increase of bisoxonol fluorescence was not modified by atropine. Release of noradrenaline by paeoniflorin from noradrenergic nerve terminals was characterized. These findings suggest that paeoniflorin can stimulate tetrodotoxin-sensitive depolarization of membranes to result in a calcium-dependent and cyclic-AMP-related release of noradrenaline from noradrenergic nerve terminals.

Metabolism of constituents in Huangqin-Tang, a prescription in traditional Chinese medicine, by human intestinal flora

In the course of studies on the metabolism of active components of Huangqin-Tang by human intestinal flora (HIF), Huangqin-Tang and all individual herbs in the decoctions were incubated with a human fecal suspension separately. By using a high-performance liquid chromatographic (HPLC) method which was previously established in our laboratory, the metabolites in both the compound prescription and all the single herb decoctions were identified and determined both qualitatively and quantitatively. We found that the constituents of Huangqin-Tang, incluing baicalin (baicalein 7-glucuronide; BG), wogonoside (wogoninoglucuronide; WG), oroxylin-A-glucuronide (OG) from Scutellariae Radix, paeoniflorin (PF) from Paeoniae Radix, liquiritin (liquiritigenin 4'-O-glucoside; LG), isoliquirtin (isoliquiritigenin 4-glucoside; ILG) and glycyrrhizic acid (GL) from Glycyhhizea Radix, were converted to their metabolites baicalein (B), wogonin (W), oroxylin-A (O), paeonimetabolin-I (PM-I), liquiritigenin (L), isoliquiritigenin (IL) and glycyrrhetinic acid (GA) by HIF. The contents of the metabolites in Huangqin-Tang and in each single herb decoction increased significantly after incubation with intestinal flora. Comparing with single herb decoctions, the transformation of BG, WG, OG, LG and ILG in the compound prescription was promoted, however, that of PF and GL was inhibited. All the results suggested that the glycosides of many medicinal herbs could be converted to aglycones by HIF, and the metabolism of most glycosides was improved in the compound prescription.

Metabolism of kalopanaxsaponin K by human intestinal bacteria and antirheumatoid arthritis activity of their metabolites

When kalopanaxsaponin K (KPK) from Kalopanax pictus was incubated for 24 h at 37 degrees C with human intestinal microflora, KPK was mainly metabolized to kalopanaxsaponin I (KPI) via kalopanaxsaponin H (KPH) rather than via kalopanaxsaponin J (KPJ), and then transformed to kalopanaxsaponin A (KPA) and hederagenin. Bacteroides sp., and Bifidobacterium sp. and Fusobacterium sp. transformed KPK to KPI and KPA and hederagenin via KPH or KPJ. However, Lactobacillus sp. and Streptococcus sp. transformed KPK to KPI, KPA, and hederagenin only via KPJ. The metabolite KPA of KPK showed potent antirheumatoid arthritis activity.

New paeonilactone-A adducts formed by anaerobic incubation of paeoniflorin with Lactobacillus brevis in the presence of arylthiols

During the course of preparing anticonvulsant paeonimetabolin-I adducts, new paeonilactone-A adducts: 9-phenylthiopaeonilactone-A, 9-(o-tolylthio)paeonilactone-A, 9-(m-tolylthio)paeonilactone-A, 9-(p-tolylthio)-paeonilactone-A and 9-(2-naphthylthio)paeonilactone-A, were obtained along with expected paeonimetabolin-I adducts by anaerobic incubation of paeoniflorin from peony roots with Lactobacillus brevis in the presence of the aromatic thiols, phenylthiol, o-tolylthiol, m-tolylthiol, p-tolylthiol and 2-naphthylthiol. The structures of these compounds were determined by spectroscopic methods including two dimensional (2D) NMR.

In-vivo assessment of extrahepatic metabolism of paeoniflorin in rats: relevance to intestinal floral metabolism

The extraction ratios of paeoniflorin in gut wall (EG), liver (EH) and lung (EL) were assessed by comparing AUCs after various routes of its administration to estimate the first-pass effects and the metabolism by intestinal flora. Pulmonary extraction ratio of paeniflorin was assessed by comparing AUCs calculated from venous and arterial plasma concentrations after its intravenous administration (0.5 mg kg-1). The mean pulmonary extraction ratio was estimated to be 0.06. The hepatic extraction ratio (EH was assessed by comparing AUCs after intraportal and intravenous administrations (0.5 and 5 mg kg-1). The plasma concentration profiles of paeoniflorin after intraportal administration were very close to those after intravenous administration, suggesting a negligible hepatic extraction ratio of paeoniflorin. The AUC value after intraperitoneal administration (0.5 mg kg-1) was greater than that after intraportal or intravenous administration. This finding suggests that paeoniflorin is not metabolized in the gut wall. The transference of paeoniflorin from the serosal side to the mucosal side was evaluated by the in-vitro everted sac method. The low intestinal permeability (19.4% at 60 min) was demonstrated by the comparison with phenobarbital (63.1% at 60 min). We conclude that paeoniflorin is not metabolize by gut wall, liver and lung, its poor absorption from the intestine results in extremely low bioavailability and the unabsorbed fraction of paeoniflorin is degraded by the intestinal flora.

Absorption and excretion of paeoniflorin in rats

The absorption and excretion of paeoniflorin after intravenous and oral administration was studied in rats to evaluate the significance of paeoniflorin in the pharmacological action of Paeony root. The plasma concentration of paeoniflorin after intravenous administration at the doses of 0.5, 2.0 and 5.0 mg kg-1 rapidly decreased, simulated by a biexponential curve, with mean terminal half-lives of 11.0, 9.9 and 12.6 min, respectively. The Vdss values were 0.332, 0. 384 and 0.423 L kg-1 and the CLtot values were 26.1, 31.2 and 30.3 mL min-1 kg-1 at each dose. When given orally at the same doses, the absolute bioavailability values (F) determined by the AUC were 0.032, 0.033 and 0.038, respectively. The cumulative urinary and faecal excretions of paeoniflorin at the dose of 5 mg kg-1 after intravenous administration were 50.5 and 0.22% of the dose within 72 h, and 1.0 and 0.08% of the dose after oral administration within 48 h, respectively. Cumulative biliary excretion after intravenous or oral administration at a dose of 0.5 mg kg-1 was 6.9 and 1.3% of the dose within 24 h, respectively. The total CLR and CLB value after intravenous dosing was less than the CLtot value. These findings suggest that paeoniflorin is metabolized in other organs as well as in the liver. We conclude that paeoniflorin absorbed is excreted mainly in urine, it has a low bioavailability and the metabolites may be involved in the pharmacological action of Paeony root.