In Vitro Study of the Metabolic Characteristics of Eight Isoquinoline Alkaloids from Natural Plants in Rat Gut Microbiota.

Gut microbiota is populated with an immense number of microorganisms, which can be regulated by dietary components and drugs to markedly affect the nutritional and health status of the host. Eight medicinal isoquinoline alkaloids from natural plants were cultured anaerobically with rat gut microbiota and an LC/MSn-IT-TOF technique was used to identify the resulting metabolites. Palmatine, tetrahydropalmatine, dauricine, and tetrandrine containing nitro-hexatomic isoquinoline rings could be easily transformed by the intestinal flora in vitro and a total of nine demethylated metabolites were detected. However, sinomenine, homoharringtonine, harringtonine, and galanthamine, which all contained benzazepine, could not undergo demethylation. Computer-assisted docking was used to analyze the binding between these compounds and sterol 14α-demethylase. The computational results demonstrated that hydrophobic interactions were the main driving force for binding, but the steric hindrance produced by the benzazepine structure resulted in a weak interaction between the hit compounds and the enzyme. This work illustrated that gut microbiota were important in the metabolism of isoquinoline alkaloids.

Interaction effects on cytochrome P450 both in vitro and in vivo studies by two major bioactive xanthones from Halenia elliptica D. Don.

The major components, 1-hydroxy-2,3,5-trimethoxy-xanthone (HM-1) and 1,5-dihydroxy-2,3-dimethoxy-xanthone (HM-5) isolated from Halenia elliptica D. Don (Gentianaceae), could cause vasodilatation in rat coronary artery with different mechanisms. In this work, high-performance liquid chromatography coupled to ion trap time-of-flight mass spectrometry (LCMS-IT-TOF) was used to clarify the metabolic pathways, and CYP450 isoform involvement of HM-1 and HM-5 were also studied in rat. At the same time, in vivo inhibition effects of HM-1 and ethyl acetate extracts from origin herb were studied. Three metabolites of HM-5 were found in rat liver microsomes (RLMs); demethylation and hydroxylation were the major phase I metabolic reactions for HM-5. Multiple CYP450s were involved in metabolism of HM-1 and HM-5. The inhibition study showed that HM-5 inhibited Cyp1a2, 2c6 and 2d2 in RLMs. HM-1 inhibited activities of Cyp1a2, Cyp2c6 and Cyp3a2. In vivo experiment demonstrated that both HM-1 and ethyl acetate extracts could inhibit Cyp3a2 in rats. In conclusion, the metabolism of xanthones from the origin herb involved multiple CYP450 isoforms; in vitro, metabolism of HM-5 was similar to that of its parent drug HM-1, but their inhibition effects upon CYP450s were different; in vivo, Cyp3a2 could be inhibited by HM-1 and ethyl acetate extracts.

In Vivo Metabolite Profiling of a Purified Ellagitannin Isolated from Polygonum capitatum in Rats.

Ellagitannin is a common compound in food and herbs, but there are few detailed studies on the metabolism of purified ellagitannins. FR429 is a purified ellagitannin with antitumor potential, which is from Polygonum capitatum Buch.-Ham.ex D. Don. The present study was designed to investigate the metabolic profiles of FR429 in rats in vivo. Using liquid chromatography coupled to ion trap time-of-flight mass spectrometry (LC/MS(n)-IT-TOF), total eight metabolites were found in rat bile and urine after intravenous administration of FR429, but could not be detected in plasma. These metabolites were ellagic acid, mono-methylated FR429, ellagic acid methyl ether glucuronide, ellagic acid methyl ether diglucuronide, ellagic acid dimethyl ether glucuronide, and ellagic acid dimethyl ether diglucuronide. It was concluded that methylation and subsequent glucuronidation were the major metabolic pathways of FR429 in rats in vivo. This is the first report on the in vivo metabolism of the purified ellagitannin in rats.

Effect of Berberine on promoting the excretion of cholesterol in high-fat diet-induced hyperlipidemic hamsters.

BACKGROUND: Berberine (BBR), as a new medicine for hyperlipidemia, can reduce the blood lipids in patients. Mechanistic studies have shown that BBR activates the extracellular-signal regulated kinase pathway by stabilizing low-density-lipoprotein receptor mRNA. However, aside from inhibiting the intestinal absorption of cholesterol, the effects of BBR on other metabolic pathways of cholesterol have not been reported. This study aimed to investigate the action of BBR on the excretion of cholesterol in high-fat diet-induced hyperlipidemic hamsters. METHODS: Golden hamsters were fed a high-fat diet (HFD) for 6 weeks to induce hyperlipidemia, followed by oral treatment with 50 and 100 mg/kg/day of BBR or 10 and 30 mg/kg/day of lovastatin for 10 days, respectively. The levels of total cholesterol (TC), triglyceride (TG), low-density lipoprotein cholesterol (LDL-C), transaminases, and total bile acid in the serum, liver, bile and feces were measured using an enzyme-linked immunosorbent assay. The cholesterol (as well as coprostanol) levels in the liver, bile and feces were determined by gas chromatography-mass spectrometry. RESULTS: The HFD hamsters showed significantly hyperlipidemic characteristics compared with the normal hamsters. Treatment with BBR for 10 days reduced the serum TC, TG and LDL-C levels in HFD hamsters by 44-70, 34-51 and 47-71%, respectively, and this effect was both dose- and time-dependent. Initially, a large amount of cholesterol accumulated in the hyperlipidemic hamster livers. After BBR treatment, reductions in the liver cholesterol were observed by day 3 and became significant by day 7 at both doses (P < 0.001). Meanwhile, bile cholesterol was elevated by day 3 and significantly increased at day 10 (P < 0.001). BBR promoted cholesterol excretion from the liver into the bile in hyperlipidemic hamsters but not in normal hamsters, and these results provide a link between the cholesterol-lowering effect of BBR with cholesterol excretion into the bile. CONCLUSIONS: We conclude that BBR significantly promoted the excretion of cholesterol from the liver to the bile in hyperlipidemic hamsters, which led to large decreases in the serum TC, TG and LDL-C levels. Additionally, compared with lovastatin, the BBR treatment produced no obvious side effects on the liver function.

Biotransformation and in vitro metabolic profile of bioactive extracts from a traditional Miao-nationality herbal medicine, Polygonum capitatum.

Polygonum capitatum Buch.-Ham.ex D. Don, a traditional Miao-nationality herbal medicine, has been widely used in the treatment of various urologic disorders. Recent pharmacological studies demonstrated that a pure compound, FR429, isolated from the ethanol extracts of P. capitatum could selectively inhibit the growth of four hepatocellular carcinoma (HCC) cell lines in a dose-dependent manner. Thus, P. capitatum probably exhibits potential antitumor activity. However, there is very little information on the metabolism of substances present in P. capitatum extracts. In this study, gallic acid, quercetrin, ethanol extracts and ethyl acetate fraction of ethnolic extract (EtOAc fraction) of P. capitatum were cultured anaerobically with rat intestinal bacteria. A highly sensitive and selective liquid chromatography electrospray ionization-ion trap-time of fight mass spectrometry (LC/MSn-IT-TOF) technique was employed to identify and characterize the resulting metabolites. A total of 22 metabolites (M1-M22), including tannins, phenolic acids and flavonoids, were detected and characterized. The overall results demonstrated that the intestinal bacteria played an important role in the metabolism of P. capitatum, and the main metabolic pathways were hydrolysis, reduction and oxidation reactions. Our results provided a basis for the estimation of the metabolic transformation of P. capitatum in vivo.

Morinda officinalis oligosaccharides increase serotonin in the brain and ameliorate depression via promoting 5-hydroxytryptophan production in the gut microbiota.

Morinda officinalis oligosaccharides (MOO) are an oral drug approved in China for the treatment of depression in China. However, MOO is hardly absorbed so that their anti-depressant mechanism has not been elucidated. Here, we show that oral MOO acted on tryptophan â†’ 5-hydroxytryptophan (5-HTP) â†’ serotonin (5-HT) metabolic pathway in the gut microbiota. MOO could increase tryptophan hydroxylase levels in the gut microbiota which accelerated 5-HTP production from tryptophan; meanwhile, MOO inhibited 5-hydroxytryptophan decarboxylase activity, thus reduced 5-HT generation, and accumulated 5-HTP. The raised 5-HTP from the gut microbiota was absorbed to the blood, and then passed across the blood-brain barrier to improve 5-HT levels in the brain. Additionally, pentasaccharide, as one of the main components in MOO, exerted the significant anti-depressant effect through a mechanism identical to that of MOO. This study reveals for the first time that MOO can alleviate depression via increasing 5-HTP in the gut microbiota.

Gut Microbiota-Mediated Personalized Treatment of Hyperlipidemia Using Berberine.

Nitroreductases (NRs) are bacterial enzymes that reduce nitro-containing compounds. We have previously reported that NR of intestinal bacteria is a key factor promoting berberine (BBR) intestinal absorption. We show here that feeding hamsters with high fat diet (HFD) caused an increase in blood lipids and NR activity in the intestine. The elevation of fecal NR by HFD was due to the increase in either the fraction of NR-producing bacteria or their activity in the intestine. When given orally, BBR bioavailability in the HFD-fed hamsters was higher than that in those fed with normal chow (by +72%, *P<0.05). BBR (100 mg/kg/day, orally) decreased blood lipids in the HFD-fed hamsters (**P<0.01) but not in those fed with normal diet. Clinical studies indicated that patients with hyperlipidemia had higher fecal NR activity than that in the healthy individuals (**P<0.01). Similarly, after oral administration, the blood level of BBR in hyperlipidemic patients was higher than that in healthy individuals (*P<0.05). Correlation analysis revealed a positive relationship between blood BBR and fecal NR activity (r=0.703). Thus, the fecal NR activity might serve as a biomarker in the personalized treatment of hyperlipidemia using BBR.

Berberine-induced bioactive metabolites of the gut microbiota improve energy metabolism.

OBJECTIVE: Berberine (BBR) clinically lowers blood lipid and glucose levels via multi-target mechanisms. One of the possible mechanisms is related to its effect on the short chain fatty acids (SCFAs) of the gut microbiota. The goal of this study is to investigate the therapeutic effect and mode of action of BBR working through SCFAs of the gut microbiota (especially, butyrate). METHODS: Gas chromatography (GC) was used to detect butyrate and other SCFAs chemically. The effect of BBR on butyrate production was investigated in vitro as well as in several animal systems. Microarrays were used to analyze the composition change in the intestinal bacteria community after treatment with BBR. BBR-induced change in the energy production and gene regulation of intestinal bacteria was examined in order to elucidate the underlying molecular mechanisms. RESULTS: We show that oral administration of BBR in animals promoted the gut microbiota to produce butyrate, which then enters the blood and reduces blood lipid and glucose levels. Incubating gut bacterial strains in vitro with BBR increased butyrate production. Orally treating animals directly with butyrate reduced blood lipid and glucose levels through a mechanism different from that of BBR. Intraperitoneal BBR administration did not increase butyrate but reduced blood lipid and glucose levels, suggesting that BBR has two modes of action: the direct effect of the circulated BBR and the indirect effect working through butyrate of the gut microbiota. Pre-treating animals orally with antibiotics abolished the effect of BBR on butyrate. A mechanism study showed that BBR (given orally) modified mice intestinal bacterial composition by increasing the abundance of butyrate-producing bacteria. Furthermore, BBR suppressed bacterial ATP production and NADH levels, resulting in increased butyryl-CoA and, eventually, butyrate production via upregulating phosphotransbutyrylase/butyrate kinase and butyryl-CoA:acetate-CoA transferase in bacteria. CONCLUSION: Promotion of butyrate (etc) production in gut microbiota might be one of the important mechanisms of BBR in regulating energy metabolism.

Transforming berberine into its intestine-absorbable form by the gut microbiota.

The gut microbiota is important in the pathogenesis of energy-metabolism related diseases. We focused on the interaction between intestinal bacteria and orally administered chemical drugs. Oral administration of berberine (BBR) effectively treats patients with metabolic disorders. However, because BBR exhibits poor solubility, its absorption mechanism remains unknown. Here, we show that the gut microbiota converts BBR into its absorbable form of dihydroberberine (dhBBR), which has an intestinal absorption rate 5-fold that of BBR in animals. The reduction of BBR to dhBBR was performed by nitroreductases of the gut microbiota. DhBBR was unstable in solution and reverted to BBR in intestine tissues via oxidization. Heat inactivation of intestinal homogenate did not inhibit dhBBR oxidization, suggesting the process a non-enzymatic reaction. The diminution of intestinal bacteria via orally treating KK-Ay mice with antibiotics decreased the BBR-to-dhBBR conversion and blood BBR; accordingly, the lipid- and glucose-lowering efficacy of BBR was reduced. Conclusively, the gut microbiota reduces BBR into its absorbable form of dhBBR, which then oxidizes back to BBR after absorption in intestine tissues and enters the blood. Thus, interaction(s) between the gut microbiota and orally administrated drugs may modify the structure and function of chemicals and be important in drug investigation.

Metabolite profiling analysis of FR429, an ellagitannin purified from Polygonum capitatum, in rat and human liver microsomes, cytosol and rat primary hepatocytes in vitro.

FR429, an ellagitannin (a type of polyphenol), is isolated and purified from Polygonum capitatum Buch.-Ham.ex D. Don which is the original herbal medicine of the "Re-Lin-Qing" formula used clinically to treat urinary tract infection in China. FR429 has been investigated for its antitumor potential in tumor-bearing nude mice in vivo, but its in vitro anti-tumor effect in hepatoma cell lines was low. Thus, it was of our interest to investigate its metabolism pathways for supporting its in vivo antitumor potential. The metabolic profiles of FR429 were studied in vitro by liquid chromatography coupled to ion trap time-of-flight mass spectrometry. Total eight metabolites were identified in rat and human liver microsomes, cytosol, and rat primary hepatocytes in vitro. Ellagic acid, a reported anti-angiogenic agent, was one of the main metabolites in these biological matrices. Methylated metabolites catalyzed by catechol-O-methyl transferase (COMT) were observed mainly in the in vitro incubation with rat liver cytosol, which was verified by using a COMT specific inhibitor entacapone and supported by molecular docking analysis. Methylated and sulfated metabolites were also found in rat primary hepatocytes in a time-dependent manner. In conclusion, the in vitro metabolism pathways of FR429 were hydrolysis, methylation and sulfation. The anti-tumor effects of its major metabolites should be further studied.

In vitro identification of cytochrome P450 isoforms responsible for the metabolism of 1-hydroxyl-2,3,5-trimethoxy-xanthone purified from Halenia elliptica D. Don.

1-Hydroxyl-2,3,5-trimethoxyxanthone (HM-1) is one of the main constituents extracted from Halenia elliptica D. Don, which is a traditionally used Tibetan medicinal plant. The aim of this study was to illustrate the proposed metabolic pathways of HM-1 and identify which cytochrome P450 (CYP450) isoforms involved in its metabolism by using pooled human liver microsomes (HLMs) and recombinant CYP450 isoforms with selective chemical inhibitors. Metabolites were identified by high performance liquid chromatography coupled to ion trap time-of-flight mass spectrometry (LCMS(n)-ESI-IT-TOF) and nuclear magnetic resonance spectroscopy (hydrogen-1 NMR and carbon-13 NMR). Three metabolites (M1-M3) were identified, which demonstrated that demethylation and hydroxylation were the major Phase I metabolic reactions for HM-1 in HLMs. The structure of another metabolite (M4) was still unclear. The enzymatic kinetics of M1 (K(m)=23.19±14.20 µM) and M2 (Km=32.06±17.09 µM) exhibited substrate inhibition; whereas, the formation of M3 (K(m)=5.73±0.70 µM) and M4 (K(m)=16.43±5.12 µM) displayed Michaelis-Menten kinetics. The intrinsic clearance (V(max)/K(m)) of M3 was highest among these metabolites, suggesting that M3 was the major metabolite of HM-1. Moreover, CYP3A4 and CYP2C8 were the primary CYP450 isoform responsible for the metabolism of HM-1. CYP1A2, CYP2A6, CYP2B6, CYP2C9 and CYP2C19 were also involved in HM-1 metabolism, especially in the formation of M3. This study finally provides evidence of substrate inhibition and metabolism-based drug-drug interaction for the medicinal preparations containing HM-1 used in clinic.

Tissue distribution of berberine and its metabolites after oral administration in rats.

Berberine (BBR) has been confirmed to have multiple bioactivities in clinic, such as cholesterol-lowering, anti-diabetes, cardiovascular protection and anti- inflammation. However, BBR's plasma level is very low; it cannot explain its pharmacological effects in patients. We consider that the in vivo distribution of BBR as well as of its bioactive metabolites might provide part of the explanation for this question. In this study, liquid chromatography coupled to ion trap time-of-flight mass spectrometry (LC/MS(n)-IT-TOF) as well as liquid chromatography that coupled with tandem mass spectrometry (LC-MS/MS) was used for the study of tissue distribution and pharmacokinetics of BBR in rats after oral administration (200 mg/kg). The results indicated that BBR was quickly distributed in the liver, kidneys, muscle, lungs, brain, heart, pancreas and fat in a descending order of its amount. The pharmacokinetic profile indicated that BBR's level in most of studied tissues was higher (or much higher) than that in plasma 4 h after administration. BBR remained relatively stable in the tissues like liver, heart, brain, muscle, pancreas etc. Organ distribution of BBR's metabolites was also investigated paralleled with that of BBR. Thalifendine (M1), berberrubine (M2) and jatrorrhizine (M4), which the metabolites with moderate bioactivity, were easily detected in organs like the liver and kidney. For instance, M1, M2 and M4 were the major metabolites in the liver, among which the percentage of M2 was up to 65.1%; the level of AUC (0-t) (area under the concentration-time curve) for BBR or the metabolites in the liver was 10-fold or 30-fold higher than that in plasma, respectively. In summary, the organ concentration of BBR (as well as its bioactive metabolites) was higher than its concentration in the blood after oral administration. It might explain BBR's pharmacological effects on human diseases in clinic.

Excretion of berberine and its metabolites in oral administration in rats.

Berberine (BBR) has been confirmed to show extensive bioactivities for the treatments of diabetes and hypercholesterolemia in clinic. However, there are few pharmacokinetic studies to elucidate the excretions of BBR and its metabolites. Our research studied the excretions of BBR and its metabolites in rats after oral administration (200 mg/kg). Metabolites in bile, urine, and feces were detected by liquid chromatography coupled to ion trap time-of-flight mass spectrometry; meanwhile, a validated liquid chromatography coupled with tandem mass spectrometry method was developed for their quantifications. Sixteen metabolites, including 10 Phase I and six Phase II metabolites were identified and clarified after dosing in vivo. Total recovered rate of BBR was 22.83% (19.07% of prototype and 3.76% of its metabolites) with 9.2 × 10(-6) % in bile (24 h), 0.0939% in urine (48 h), and 22.74% in feces (48 h), respectively. 83% of BBR was excreted as thalifendine (M1) from bile, whereas thalifendine (M1) and berberrubine (M2) were the major metabolites occupying 78% of urine excretion. Most of BBR and its metabolites were found in feces containing 84% of prototype. In summary, we provided excretion profiles of BBR and its metabolites after oral administration in rats in vivo.

Identification of metabolites of FR429, a potential antitumor ellagitannin, transformed by rat intestinal bacteria in vitro, based on liquid chromatography-ion trap-time of flight mass spectrometry analysis.

FR429 is an ellagitannin with a potential antitumor activity, isolated and purified from Polygonum capitatum Buch.-Ham.ex D.Don, which is a traditional Miao-nationality herbal medicine in Guizhou and Yunnan of China. Our preliminary result of pharmacology study has indicated that the antitumor activity of FR429. However, the metabolism of FR429 has not been reported yet. In this study, LC-ion trap-time of flight mass spectrometry (LC-IT-TOF/MS) was used to characterize unpredictable metabolites of FR429 biotransformed by intestinal bacteria in vitro. Total thirteen metabolites were detected and characterized via comparisons of their accurate molecular masses and fragment ions of each MS(n) stage with those of the parent drug, and four of them were also elucidated by NMR. The results demonstrated that FR429 could be transformed by intestinal bacteria in vitro, mainly via hydrolysis and reduction reaction. This work provided a basis for the further study on the biotansformation of FR429 in vivo.