Research progress on the interactions between gut bacterial β-glucuronidases and Chinese herbal medicines / 药学学报

In traditional oral practice, the presystemic interactions with gut microbiota is an important mechanism underlying the holistic health benefits of Chinese herbal medicines (CHMs), making the study of CHMs distinct from the research of Western medicines of which the systemic exposure (level in blood) is the starting point and the core. Gut microbial metabolism complements host metabolism in maintaining metabolic homeostasis of many biologically important endogenous molecules and the disposition of numerous exogenous compounds. Among them, the widely distributed gut bacterial β-glucuronidases (BGUSs) coordinate with host UDP-glucuronosyltransferases (UGTs) to play a role in the occurrence and intervention of diseases by affecting the glucuronidation homeostasis and altering the intestinal local and/or systemic exposure of endogenous compounds and xenobiotics. On one hand, many ingredients of CHMs undergo enterohepatic circulation; On the other hand, CHMs can act on BGUSs directly or indirectly change the distribution and function of BGUSs through reprogramming gut microbiome. The multiple interactions between BGUSs and CHMs may play an important role in the overall therapeutic benefits of CHMs. This work firstly summarizes the latest research progress on BGUSs; then the physiological, pathological and pharmacological significance of BGUSs are exemplified with representative endogenous and exogenous compounds from the aspects of nutrient utilization, metabolic homeostasis, and therapeutic response based on the varied substrate spectra of BGUSs; finally, the scattered data in literature were integrated to summarize the multiple interactions between BGUSs and CHMs, highlighting the important role of BGUSs in the holistic actions of CHMs.

Advances in metabolism of natural flavonoid glycosides / 中草药

Flavonoid glycosides (FGs) are secondary metabolites of many plants widely found in nature, and exhibit significant biological activities, such as anticancer, antioxidant and antimicrobial. According to the glycosidic bonds, FGs are divided into flavonoid O-glycosides and flavonoid C-glycosides. The main metabolic processes of FGs in vivo were specific hydrolysis in the gastrointestinal tract and glucuronidation in liver. Glucose, xylose, rhamnose and other glycosyl groups were hydrolyzed to produce secondary glycosides or aglycones in the gastrointestinal tract that were absorbed into blood, and then further glucuronidation and methylation metabolites are mainly produced by phase II metabolism in liver. This article reviews the metabolism in vivo and biotransformation in vitro of some typical natural flavonoid glycosides exited in Chinese materia medica (CMMs), such as flavonoid O-glycosides in Epimedii Folium, Glycyrrhizae Radix et Rhizoma, Scutellariae Radix, Citri Reticulatae Pericarpium, and Cirsii Japonici Herba, and flavonoid C-glycosides in Anemarrhenae Rhizoma and Puerariae Lobatae Radix. The investigation of the metabolisms of FGs in vivo is helpful for the clarification of the effective ingredients in CMMs, which will provide the basis for new drugs development based on metabolites in vivo.

Study on metabolic pathways of salidroside in rats / 中草药

Objective: To analyze the metabolic pathways of salidroside when gavaged to rats, and to identify its in vivo metabolites. Methods: A UPLC-Q-TOF-MS method was established and applied to identify the metabolites of salidroside in bile, urine, feces, and plasma samples after ig administration of salidroside 200 mg/kg to rats. Results: A total of 20 metabolites were characterized in rats. The dominant metabolic pathways of salidroside include glucuronidation, acetylation, sulfation, and methylation. Conclusion: Salidroside undergoes extensive phases I and II metabolism in rats. The main excretion path is the phase II conjugated metabolites via urine, feces, and bile. The parent drug of salidroside is the main exposure material in plasma.

In vivo metabolic pathway of naringenin in rats / 中草药

Objective: To study the in vivo metabolic pathway of naringenin in rats, which would provide reference for its further research and development. Methods: A liquid chromatography with hybrid quadruple-linear ion trap mass spectrometer (LC-QTRAP-MS) was applied to identify the metabolites of naringenin in bile, urine, feces and plasma after ig administration to rats. The fragmentation patterns of naringenin were also used to analyze possible metabolic pathways in the study. Results: There were altogether 14 metabolites detected. The possible metabolic pathways of naringenin were oxidation, methylation, glucuronidation and sulfation in rats. Conclusion: In vivo metabolism studies show that naringenin undergoes extensive metabolism, including phase I and phase II biotransformation, and the phase II glucuronide and sulfate conjugates are primary metabolites. The relative quantitative amounts of metabolites excreted from urine are almost equivalent to that of the parent naringenin, while a large majority of metabolites are conjugated ones in bile, which are subsequently transformed to the parent in intestinal tract and appeared in feces.

Study on O-glucuronidation pathways of alkannin / 中草药

Objective: To investigate and characterize the O-glucuronidation pathways of the S-stereoisomer of shikonin (alkannin). Methods: Liquid chromatography and mass spectrometry were employed for the detection of akannin and its glucuronide. The incubation of alkannin in human liver microsomes (HLM), human kidney microsomes (HKM) and recombinant human UDP-glucuronyltransferases (UGT) were employed for the study of metabolism profile, the involved UGT isoforms and kinetic analysis. Recombinant human UGT screening, correlation study and chemical inhibition experiments were used for elucidation the selectivity of UGT isoform towards alkannin. Results: In the incubation of alkannin in HLM with the presence of UDPGA, a single UGT metabolite was detected. The screening of the recombinant human UGTs found that UGT1A9 high selectively catalyzed the glucuronidation of alkannin. Kinetic analysis revealed the kinetic of alkannin in HLM, HKM and recombinant UGT1A9 all followed substrate inhibition model and the Km values were 3.75-4.50 μmol/L. The glucuronidation of alkannin and propofol, a probe substrate of UGT1A9, in 12 individual HLM showed really good correlation, the correlation coefficient R2 was 0.88. Chemical inhibition experiments indicated that HLM magnolol and niflumic acid showed obvious inhibition to alkannin glucuronidation; Testerone, celastrol, and nilotinib did not inhibit alkannin glucuronidation. Conclusion: This study finds that UGT metabolism is an important metabolism pathway of alkannin in human, and alkannin is a highly selective probe substrate of human UGT1A9.

Identification of in vivo substances of rats after oral administration of mulberry leaves flavonoids by uplc-q-tof/ms / 中草药

Objective To identify the chemical substances in plasma, urine, feces and bile samples of rats after oral administration of mulberry leaves flavonoids. Methods The plasma, urine, feces and bile samples of rats after a single oral administration of mulberry leaves flavonoids at a dose of 0.5 g/kg at different time points were detected by UPLC-Q-TOF/MS. Results Thirteen prototype compounds and 41 metabolites were found. The metabolites mainly included glucuronidation, sulfation and methylation. Conclusion This reseach estabilished the basis to study the pharmacokinetics and the pharmacological action mechanism of the mulberry leaves.

Glucuronidation is the dominating in-vivo metabolism pathway of herbacetin:elucidation of herbacetin pharmacokinetics after intravenous and oral administration in rats / 中国药理学与毒理学杂志

OBJECTIVE To map a comprehensive metabolic pathway of herbacetin in rats, specifically, to elucidate the biotransformation of herbacetin in vivo and to simultaneously monitor the pharmacokinetic process of both parent drug and its major metabolites. METHODS liquid chromatography/ion trap mass spectrometry (LC/MSn) and ultra-liquid chromatography coupled with mass spectrometry (UPLC/MS) were combined in the current study for qualitative and quantitative determinations of herbacetin and its metabolites in bile, urine and feces after both oral and intravenous administration of herbacetin to rats. Enzyme kinetic studies on the intestinal and hepatic metabolism of herbacetin were further conducted to elucidate metabolic profiles of herbacetin in rat tissues and organs. Additionally, plasma concentration profiles of herbacetin and its metabolites in rats were obtained to characterize the overall pharmacokinetic behavior of herbacetin. RESULTS It was found that herbacetin was excreted primarily from rat urine in the form of glucuronide-conjugations. Subsequent in vitro enzyme kinetic studies and in vivo pharmacokinetic investigations suggested an extensive hepatic metabolism of herbacetin and the high exposure of herbacetin- glucuronides in systemic circulation. The clearance, half- life and bioavailability of herbacetin in rats were determined as (16.4±1.92)mL·kg-1·min-1, (11.9±2.7)min, and 1.32%, respectively. On basis of these findings, a comprehensive metabolic pathway of herbacetin in rats was composed. In addition, a physiology based pharmacokinetic (PBPK) model was successfully developed with the aid of the GastroPlus to simulate the pharmacokinetic process of herbacetin in rats. Application of the PBPK modeling can provide a useful starting point to understand and extrapolate pharmacokinetic parameters among different species, populations, and disease states. CONCLUSION After oral administration, herbacetin was subjected to colonic degradation and extensive first pass metabolism, with glucuronidation as its dominating in vivo metabolic pathway.

Drug glucuronidation and disposition in brain / 药学学报

UDP-glucuronosyltransferase (UGT), a kind of phase II drug-metabolizing enzyme, catalyzes the conjugation of glucuronic acid and drugs. UGTs are widely expressed in brain, but at a relatively low level compared to that in liver. Brain UGTs are inducible or inhibitable, which influences the drug distribution in the central nervous system. UGTs, cytochrome P450 (CYPs) and transporters act together to effect pharmacokinetics of drugs in brain. Several drugs have the capacity to cross the blood brain barrier after glucuronidation and certain drugs may be subject to direct glucuronidate in brain by the function of UGTs. The brain UGTs' isoforms, localization, induction, inhibition, and interaction with CYP and transporters are introduced in this review. The process of drug glucuronidation and distribution in brain is summarized for five drugs. A deep insight into the process of drug metabolism and distribution in brain may provide a valuable reference for drug design for the central nervous system.

Effect protein kinase inhibitor on luteolin glucuronidation / 中国药学杂志

OBJECTIVE: To evaluate the effect of protein kinase inhibitor on luteolin glucuronidation. METHODS: LS174T cells were treated with either curcumin or calphostin C of various concentrations. The glucuronidation metabolites of luteolin, catalyzed by the S9 of treated LS174T cells, was measured by HPL C. The expression of UGT1A in treated LS174T cells was determined by realtime PCR and western blot. RESULTS: A rapid down-regulation of luteolin glucuronidation catalyzed by LS174T cells following curcumin and calphostin C treatment was observed. However, there was no effect on the expression of UGT1A in treated LS174T cells. CONCLUSION: The glucuronidation of luteolin can be suppressed by protein kinase inhibitor indirectly. The suppression may be caused by abnormal phosphorylation of UGTs, which are catalyzed by protein kinase.

Analysis on in vivo metabolites of α-hederin in rats by UPLC-MS/MS / 中草药

Objective: To investigate the metabolites of α-hederin in feces of rats after ig administration. Methods: An UPLC-Q/Trap-MS method was used for the identification of metabolites of α-hederin in feces of rats after ig administration of α-hederin (150 mg/kg). Results: Seven metabolites were detected in rat feces, including demethylation of α-hederin (M1), 3-O-α-L-arabinopyranoside hederagenin (M2), hederagenin (M3), glucuronideconjugate of α-hederin (M4), and double bond bonus of α-hederin (M5, M6-1, and M6-2). Conclusion: α-Hederin experiences a variety of metabolic reactions in rat gastrointestinal tract, mainly including deglycosylation, glucuronidation, demethylation, etc.

Genetic Polymorphisms of UGT1A and their Association with Clinical Factors in Healthy Koreans

Glucuronidation by the uridine diphosphateglucuronosyltransferase 1A enzymes (UGT1As) is a major pathway for elimination of particular drugs and endogenous substances, such as bilirubin. We examined the relation of eight single nucleotide polymorphisms (SNPs) and haplotypes of the UGT1A gene with their clinical factors. For association analysis, we genotyped the variants by direct sequencing analysis and polymerase chain reaction (PCR) in 218 healthy Koreans. The frequency of UGT1A1 polymorphisms, -3279T>G, -3156G>A, -53 (TA)(6>7), 211G>A, and 686C>A, was 0.26, 0.12, 0.08, 0.15, and 0.01, respectively. The frequency of -118 (T)9>10 of UGT1A9 was 0.62, which was significantly higher than that in Caucasians (0.39). Neither the -2152C>T nor the -275T>A polymorphism was observed in Koreans or other Asians in comparison with Caucasians. The -3156G>A and -53 (TA)6>7 polymorphisms of UGT1A were significantly associated with platelet count and total bilirubin level (p=0.01, p=0.01, respectively). Additionally, total bilirubin level was positively correlated with occurrence of the UGT1A9-118 (T)(9>10) rare variant. Common haplotypes encompassing six UGT1A polymorphisms were significantly associated with total bilirubin level (p=0.01). Taken together, we suggest that determination of the UGT1A1 and UGT1A9 genotypes is clinically useful for predicting the efficacy and serious toxicities of particular drugs requiring glucuronidation.