Metabolic fate analysis of Huang–Lian–Jie–Du Decoction in rat urine and feces by LC–IT-MS combining with LC–FT-ICR-MS: a feasible strategy for the metabolism study of Chinese medical formula

1.?Huang–Lian–Jie–Du Decoction (HLJDD) is widely used for the treatment of hypertension, diabetes, inflammation and neural system diseases in clinic. In the present study, the comprehensive metabolic profile of HLJDD was demonstrated reliably and rapidly followed by the metabolic pathway analysis of six typical pure compounds (four alkaloids, one flavonoid and one iridoid) in HLJDD using LC–IT-MS combined with high resolution LC–FT-ICR-MS.

2.?Totally, 85 compounds, including 32 prototype components and 53 biotransformed metabolites were detected and characterized in the urine and feces after oral administration of HLJDD and six pure compounds to rats, respectively. Among them, 17 prototypes were identified definitely with standard references.

3.?Hydroxylation, demethylation and glucuronidation reactions of alkaloids, as well as glucuronidation and sulfonation reactions of iridoids and flavonoids, were observed as the major metabolic pathways of HLJDD. Flavonoids, iridoids and their metabolites were mainly excreted from urine. However, amount of alkaloids were detected in feces.

4.?In general, the distinctive metabolic process of three kinds of representative components in HLJDD was clarified. The in vivo metabolic network of HLJDD was demonstrated. Meanwhile, the investigation of representative pure compounds in metabolic study provided a valuable strategy to elucidate the full-scale metabolic fate of HLJDD. This might be helpful to understand the in vivo mechanism of Traditional Chinese medicine (TCM).     

Comprehensive characterization of the in vitro and in vivo metabolites of geniposide in rats using ultra-high-performance liquid chromatography coupled with linear ion trap–Orbitrap mass spectrometer

1.?Geniposide (genipin 1-O-glucose), one of the major bioactive constituents isolated from Fructus Gardeniae, possesses many biological activities. In this study, an efficient strategy was developed using ultra-high-performance liquid chromatography coupled with linear ion trap–Orbitrap mass spectrometer (UPLC–LTQ–Orbitrap) to profile the in vitro and in vivo metabolic patterns of geniposide in rat liver microsomes (RLMs), plasma, urine, and various tissues. And post-acquisition data-mining methods including extracted ion chromatogram (EIC), multiple mass defect filters (MMDF), fragment ion searching (FISh), and isotope pattern filtering (IPF) were adopted to characterize the known and unknown metabolites.

2.?A total of 33 metabolites were detected and interpreted according to accurate mass measurement, diagnostic fragment ions, relevant drug biotransformation knowledge, and bibliography data. Among them, 17 metabolites were detected in the plasma, 31 metabolites were identified in the urine, six metabolites could be found in rat heart, 12 in liver, three in spleen, six in lung, 12 in kidney, six in brain, and four in RLMs.

3.?A series of corresponding reactions such as hydrolysis, hydroxylation, taurine conjugation, hydrogenation, decarboxylation, demethylation, sulfate conjugation, cysteine S-conjugation, glucosylation, and their composite reactions were all discovered.

4.?The results could provide comprehensive insights and guidance for elucidation of side effect mechanism and safety monitoring as well as for rational formulation design in drug delivery system. The newly discovered geniposide metabolites could be targets for future metabolism studies on the important chemical constituents from herbal medicines.     

Structure identification and elucidation of mosapride metabolites in human urine,feces and plasma by ultra performance liquid chromatography-tandem mass spectrometry method

Abstract

1.?Mosapride citrate (mosapride) is a potent gastroprokinetic agent. The only previous study on mosapride metabolism in human reported one phase I oxidative metabolite, des-p-fluorobenzyl mosapride, in human plasma and urine using HPLC method. Our aim was to identify mosapride phase I and phase II metabolites in human urine, feces and plasma using UPLC-ESI-MS/MS.

2.?A total of 16 metabolites were detected. To the best of our knowledge, 15 metabolites have not been reported previously in human.

3.?Two new metabolites, morpholine ring-opened mosapride (M15) and mosapride N-oxide (M16), alone with one known major metabolite, des-p-fluorobenzyl mosapride (M3), were identified by comparison with the reference standards prepared by our group. The chemical structures of seven phase I and six phase II metabolites of mosapride were elucidated based on UPLC–MS/MS analyses.

4.?There were two major phase I reactions, dealkylation and morpholine ring cleavage. Phase II reactions included glucuronide, glucose and sulfate conjugation. The comprehensive metabolic pathway of mosapride in human was proposed for the first time.

5.?The metabolites in humans were compared with those in rats reported previously. In addition to M10, the other 15 metabolites in humans were also found in rats. This result suggested that there was little qualitative species difference in the metabolism of mosapride between rats and humans.

6.?In all, 16 mosapride metabolites including 15 new metabolites were reported. These results allow a better understanding of mosapride disposition in human.     

Species differences in metabolism of ripasudil (K-115) are attributed to aldehyde oxidase

1.?We examined the metabolism of ripasudil (K-115), a selective and potent Rho-associated coiled coil-containing protein kinase (ROCK) inhibitor, by in vitro and in vivo studies.

2.?First, we identified metabolites and metabolic enzymes involved in ripasudil metabolism. Species differences were observed in metabolic clearance and profiles of metabolites in liver S9 fraction and hepatocytes. In addition, ripasudil was metabolised in humans and monkey S9 without nicotinamide adenine dinucleotide phosphate (NADPH). Studies using specific inhibitors and human recombinant enzyme systems showed that M1 (main metabolite in humans) formation is mediated by aldehyde oxidase (AO).

3.?Therefore, we developed ripasudil as an ophthalmic agent. First, we compared the pharmacokinetic profiles of ripasudil in humans and rats. The results indicated rapid disappearance of ripasudil from the circulation after instillation in humans and its level remained relatively high only in M1. In contrast, we found six metabolites from M1 to M6 in plasma after oral administration to rats.

4.?Analysis of enzyme kinetics using S9 showed that the formation of M1 is the major metabolic pathway of ripasudil in humans even though CYP3A4/3A5 and CYP2C8/3A4/3A5 were associated with the formation of M2 and M4, respectively. In conclusion, AO causes differences in ripasudil metabolism between species.     

Correlative analysis of metabolite profiling of Danggui Buxue Tang in rat biological fluids by rapid resolution LC-TOF/MS

In this work, the metabolite profiles of Danggui Buxue Tang (DBT) in rat bile and plasma were qualitatively described, and the possible metabolic pathways of DBT were subsequently proposed. Emphasis was put on correlative analysis of metabolite profiling in different biological fluids. After oral administration of DBT, bile and plasma samples were collected and pretreated by solid phase extraction. Rapid resolution liquid chromatography coupled to time-of-flight mass spectrometry (RRLC-TOFMS) was used for characterization of DBT-related compounds (parent compounds and metabolites) in biological matrices. A total of 142 metabolites were detected and tentatively identified from the drug-containing bile and plasma samples. Metabolite profiling shows that rat bile contained relatively more glutathione-derived conjugates, more saponins compounds and more diverse forms of metabolites than urine. The metabolite profile in plasma revealed that glucuronide conjugates of isoflavonoids, dimmers, acetylcysteine conjugates and parent form of phthalides, as well as saponin aglycones were the major circulating forms of DBT. Collectively, the metabolite profile analysis of DBT in different biological matrices provided a comprehensive understanding of the in vivo metabolic fates of constituents in DBT.     

Excretion and metabolism of recainam, a new anti-arrhythmic drug, in laboratory animals and humans

The metabolic disposition of recainam, an antiarrhythmic drug, was compared in mice, rats, dogs, rhesus monkeys, and humans. Following oral administration of [14C]recainam-HCl, radioactivity was excreted predominantly in the urine of all species except the rat. Metabolite profiles were determined in excreta by HPLC comparisons with synthetic standards. In rodents and rhesus monkeys, urinary excretion of unchanged recainam accounted for 23-36% of the iv dose and 3-7% of the oral dose. Aside from quantitative differences attributable to presystemic biotransformation, metabolite profiles were qualitatively similar following oral or iv administration to rodents and rhesus monkeys. Recainam was extensively metabolized in all species except humans. In human subjects, 84% of the urinary radioactivity corresponded to parent drug. The major metabolites in mouse and rat urine and rat feces were m- and p-hydroxyrecainam. Desisopropylrecainam and dimethylphenylaminocarboxylamino propionic acid were the predominant metabolites in dog and rhesus monkey urine. Small amounts of desisopropylrecainam and p-hydroxyrecainam were excreted in human urine. Selective enzymatic hydrolysis revealed that the hydroxylated metabolites were conjugated to varying degrees among species. Conjugated metabolites were not present in rat urine or feces, while conjugates were detected in mouse, dog, and monkey urine. Structural confirmation of the dog urinary metabolites was accomplished by mass spectral analysis. The low extent of metabolism of recainam in humans suggests that there will not be wide variations between dose and plasma concentrations.     

Identification of the absorbed components and metabolites in rat plasma after oral administration of Rhizoma Chuanxiong decoction by HPLC-ESI-MS/MS

An HPLC-ESI-MS/MS method was established to identify the absorbed components and metabolites in rat plasma after oral administration of Rhizoma Chuanxiong decoction (RCD), a well-known traditional Chinese medicine. By comparing the extracted ion chromatograms (EICs) obtained from dosed rat plasma, blank rat plasma and RCD, a total of 25 compounds were detected in dosed rat plasma. Among them, 13 compounds were absorbed into rat plasma in prototype and identified as ferulic acid, senkyunolide J, senkyunolide I, senkyunolide D or 4,7-dihydroxy-3-butylphthalide, senkyunolide F, senkyunolide M, senkyunolide Q, senkyunolide A, E-butylidenephthalide, E-ligustilide, neocnidilide, Z-ligustilide, levistolide A, according to the retention times, UV, MS, MS/MS spectra. In addition, 12 conjugated metabolites including 6 senkyunolide I-related metabolites, 4 senkyunolide J-related metabolites and 2 butylidenephthalide-related metabolites were also detected and identified by comparing their MS, MS/MS spectra with that of corresponding original components. Conjugated with glutathione, cysteine, glucuronic acid and sulphuric acid were the main metabolic reactions of phthalides. Finally the in vivo metabolic pathways of chemical constituents of Chuanxiong in rat plasma were proposed in this study.     

Species differences in metabolism of a new antiepileptic drug candidate,DSP‐0565 [2‐(2′‐fluoro[1,1′‐biphenyl]‐2‐yl)acetamide]

The metabolism and pharmacokinetics of DSP‐0565 [2‐(2′‐fluoro[1,1′‐biphenyl]‐2‐yl)acetamide], an antiepileptic drug candidate, was investigated in rats, dogs, and humans. In human hepatocytes, [¹⁴C]DSP‐0565 was primarily metabolized via amide bond hydrolysis to (2′‐fluoro[1,1′‐biphenyl]‐2‐yl)acetic acid (M8), while in rat and dog hepatocytes, it was primarily metabolized via both hydrolysis to M8 and hydroxylation at the benzene ring or the benzyl site to oxidized metabolites. After single oral administration of [¹⁴C]DSP‐0565 to rats and dogs, the major radioactivity fraction was recovered in the urine (71–72% of dose) with a much smaller fraction recovered in feces (23–25% of dose). As primary metabolites in their excreta, M8, oxidized metabolites, and glucuronide of DSP‐0565 were detected. The contribution of metabolic pathways was estimated from metabolite profiles in their excreta: the major metabolic pathway was oxidation (57–62%) and the next highest was the hydrolysis pathway (23–33%). These results suggest that there are marked species differences in the metabolic pathways of DSP‐0565 between humans and animals. Finally, DSP‐0565 human oral clearance (CL/F) was predicted using in vitro–in vivo extrapolation (IVIVE) with/without animal scaling factors (SF, in vivo intrinsic clearance/in vitro intrinsic clearance). The SF improved the underestimation of IVIVE (fold error = 0.22), but the prediction was overestimated (fold error = 2.4–3.3). In contrast, the use of SF for hydrolysis pathway was the most accurate for the prediction (fold error = 1.0–1.4). Our findings suggest that understanding of species differences in metabolic pathways between humans and animals is important for predicting human metabolic clearance when using animal SF.     

Disposition and Metabolic Profiling of the Penetration Enhancer Azone. I. In Vivo Studies: Urinary Profiles of Hamster,Rat, Monkey,and Man

Chain-labeled ¹⁴C-Azone was intravenously administered to hamster, monkey, and rat, to compare its metabolic profile with that obtained previously in humans after dermal application. Azone-derived radioactivity was excreted predominantly in the urine for both hamster and monkey, which is similar to the disposition in humans. Metabolic profiling in urine revealed extensive systemic metabolism to occur in all species studied. The main fraction of the metabolites was most polar in man, followed by rat, monkey, and hamster. Traces of the parent compound were detectable only in hamster urine. Although some of the polar major human metabolites were also present in rat urine, the animals were unsuitable for collecting metabolites of Azone observed in humans. In rats, complete cleavage of the dodecyl side chain was ruled out by administering Azone that had been labeled at two distinct positions of the molecule. Additionally, oral administration of Azone to rats resulted in the same metabolic profile as intravenous administration, indicating that gastrointestinal metabolism does not occur or is similar to systemic metabolism.     

Investigation of 6-O-methyl-scutellarein metabolites in rats by ultra-flow liquid chromatography/quadrupole-time-of-flight mass spectrometry

Context Scutellarin (1) has been widely used in China to treat acute cerebral infarction and paralysis induced by cerebrovascular diseases. However, scutellarin (1) has unstable metabolic characteristics.

Objective The metabolic profile of 6-O-scutellarein was studied to determine its metabolic stability in vivo.

Materials and methods In this study, a method of UFLC/Q-TOF MS was used to study the 6-O-methyl-scutellarein metabolites in rat plasma, urine, bile and faeces after oral administration of 6-O-methyl-scutellarein (3). One hour after oral administration of 6-O-methyl-scutellarein (3) (34?mg/kg), approximately 1?mL blood samples were collected in EP tubes from all groups. Bile, urine and faeces samples were collected from eight SD rats during 0–24?h after oral administration. The mass defect filtering, dynamic background subtraction and information dependent acquisition techniques were also used to identify the 6-O-methyl-scutellarein metabolites.

Results The parent compound 6-O-methyl-scutellarein (3) was found in rat urine, plasma, bile and faeces. The glucuronide conjugate of 6-O-methyl-scutellarein (M1, M2), diglucuronide conjugate of 6-O-methyl-scutellarein (M3), sulphate conjugate of 6-O-methyl-scutellarein (M4), glucuronide and sulphate conjugate of 6-O-methyl-scutellarein (M5), methylated conjugate of 6-O-methyl-scutellarein (M6) were detected in rat urine. M1, M2 and M3 were detected in rat bile. M1 was found in rat plasma and M7 was detected in faeces.

Discussion and conclusion Because the parent compound 6-O-methyl-scutellarein (3) was found in rat urine, plasma, bile and faeces, we speculate that 6-O-methyl-scutellarein (3) had good metabolic stability in vivo. This warrants further study to develop it as a promising candidate for the treatment of ischemic cerebrovascular disease.     

栀子-闹羊花配伍对大鼠血浆中闹羊花毒素Ⅱ和闹羊花毒素Ⅲ的药动学影响

目的考察栀子与闹羊花配伍对闹羊花中闹羊花毒素Ⅱ和闹羊花毒素Ⅲ药动学的影响。方法建立LC-MS/MS测定大鼠血浆中闹羊花毒素Ⅱ和闹羊花毒素Ⅲ的分析方法,并用此方法测定大鼠口服给予闹羊花与栀子配伍液及闹羊花单煎液后大鼠体内的闹羊花毒素Ⅱ和闹羊花毒素Ⅲ的血药浓度,计算其药动学参数并统计分析。结果闹羊花毒素Ⅱ在1～200 ng·mL^–1、闹羊花毒素Ⅲ在1～100 ng·mL^–1内线性关系良好(r>0.999),质控样本精密度均<12%,准确度RSD<20%。栀子配伍闹羊花给药和单独给药后体内闹羊花毒素Ⅱ的AUC_0–t分别为(260.44±51.67)和(213.39±59.03) h·ng·mL^–1,闹羊花毒素Ⅲ的AUC_0–t分别为(60.97±22.78)和(22.38±5.55)h·ng·mL^–1。与闹羊花单煎给药相比,栀子与闹羊花配伍给药后闹羊花毒素Ⅱ的T_1/2和MRT₍(0–t))显著升高,闹羊...     

The metabolism of (±)-methylephedrine in rat and man

1. Urinary metabolites of methylephedrine and their excretion after oral administration to rat and human volunteers have been studied.

2. The unchanged drug, ephedrine, norephedrine, their aromatic hydroxylated compounds and methylephedrine N-oxide were found in rat urine. The same metabolites, except the p-hydroxylated metabolites, were detected in human urine. The most abundant metabolite in rat urine was methylephedrine N-oxide, and in human urine was the unchanged drug.

3. Metabolites excreted in three days after administration of the drug to rat amounted to about 54% of the dose and those after administration to man, 70-72%.     

Absorption,metabolism and excretion of darexaban (YM150), a new direct factor Xa inhibitor in humans

1.?The absorption, metabolism and excretion of darexaban (YM150), a novel oral direct factor Xa inhibitor, were investigated after a single oral administration of [¹⁴C]darexaban maleate at a dose of 60?mg in healthy male human subjects.

2.?[¹⁴C]Darexaban was rapidly absorbed, with both blood and plasma concentrations peaking at approximately 0.75?h post-dose. Plasma concentrations of darexaban glucuronide (M1), the pharmacological activity of which is equipotent to darexaban in vitro, also peaked at approximately 0.75?h.

3.?Similar amounts of dosed radioactivity were excreted via faeces (51.9%) and urine (46.4%) by 168?h post-dose, suggesting that at least approximately half of the administered dose is absorbed from the gastrointestinal tract.

4.?M1 was the major drug-related component in plasma and urine, accounting for up to 95.8% of radioactivity in plasma. The N-oxides of M1, a mixture of two diastereomers designated as M2 and M3, were also present in plasma and urine, accounting for up to 13.2% of radioactivity in plasma. In faeces, darexaban was the major drug-related component, and N-demethyl darexaban (M5) was detected as a minor metabolite.

5.?These findings suggested that, following oral administration of darexaban in humans, M1 is quickly formed during first-pass metabolism via UDP-glucuronosyltransferases, exerting its pharmacological activity in blood before being excreted into urine and faeces.     

乙烷硒啉的临床药物动力学和代谢转化特点研究

目的研究肿瘤患者口服乙烷硒啉(1,2-[bis(1,2Benzisoselenazolone-3(2H)-ketone)]ethane,BBSKE)后的药物动力学及体内代谢转化特征。方法3例肿瘤患者单次口服给药剂量为600mg.d-1,采集各个时间点的血浆样品及尿样,用液相色谱-串联四极杆质谱(LC/ESI-MS/MS)联用技术测定血浆样品中BBSKE的含量,用液相色谱-电喷雾离子阱质谱(LC-ESI/MSn)联用技术对尿及血浆中的代谢产物进行分析鉴定。结果得到了BBSKE在血浆中的药时曲线图及主要的药物动力学参数。在尿中共发现了6个BBSKE的氧化、甲基化、葡萄糖醛酸化代谢产物,在血浆中共发现了2个BBSKE的氧化、葡萄糖醛酸化代谢产物。结论BBSKE的血药浓度较低,表观分布容积大。氧化、甲基化、葡萄糖醛酸化反应是BBSKE在人体内的3种重要代谢途径。     

Species comparison of pharmacokinetics and metabolism of diltiazem in humans, dogs, rabbits, and rats

Diltiazem (DTZ) is a calcium antagonist widely used in the treatment of angina and related heart diseases. It is extensively metabolized into a host of metabolites, some of which have potent pharmacological activities. In this study, the pharmacokinetics and metabolism of DTZ was investigated in humans, dogs, rabbits, and rats after each species (n = 4 or 5) was given a single oral dose of DTZ. After the drug administration, blood and urine samples were collected for 12 and 48 hrs, respectively. DTZ and six of its metabolites were quantitated in our laboratory by HPLC. The results indicated that, in humans, the major metabolites in plasma were N-monodesmethyl diltiazem (MA), deacetyl diltiazem (M1), and deacetyl N-monodesmethyl diltiazem (M2). These metabolites were also detected in the plasma of dogs, rabbits, and rats. However, there were quantitative differences. For example, in the humans and dogs, MA was the most abundant metabolite in plasma, while M1 and M2 were most prominent in the rabbits and rats, respectively, and M2 was a relatively minor metabolite in dog plasma. Less than 5% of the dose was recovered as unchanged DTZ in the urine of all the tested species. The most abundant metabolites in urine appeared to be MA and deacetyl N,O-didesmethyl diltiazem, although there were considerable inter- and intra-species variations. Two additional metabolites were detected in the urine of the humans, dogs, and rabbits, but not in the rats. They were tentatively identified as O-desmethyl diltiazem and N-O-didesmethyl diltiazem, using electron impact and ammonia chemical ionization mass spectrometry.(ABSTRACT TRUNCATED AT 250 WORDS)     

Biotransformation of BOF-4272, a sulfoxide-containing drug, in the cynomolgus monkey.

BOF-4272, (+/-)-8-(3-methoxy-4-phenylsulfinylphenyl) pyrazolo[1,5-a]-1,3,5-triazine-4(1H)-one), is a new drug intended for the treatment of hyperuricemia. This report describes the pharmacokinetics and detailed metabolic pathways of BOF-4272 in the cynomolgus monkey, which were investigated using the metabolites found in plasma, urine, and faeces after intravenous and oral administration. M-4 was the main metabolite in plasma after intravenous administration. M-3 and M-4 were the main metabolites in plasma after oral administration. The Cmax and AUC(0-t) of M-4 were the highest of all the metabolites after intravenous administration. The Cmax and AUC(0-t) of M-3 were the highest of all the metabolites, and those of M-4 were the second highest, after oral administration. M-4 and M-3 were the main metabolites detected in urine and faeces, respectively, after intravenous administration, with M-4 and M-3 at 47.2% in urine and 19.1% in faeces, respectively, within 120 h after administration. M-4 was the only metabolite detected in urine after oral administration, at about 5% within 120 h after administration. M-3 was detected in faeces at 17.0% within 120 h after oral administration. These results suggest that, in the cynomolgus monkey, BOF-4272 is rapidly biotransformed to a main metabolite (M-4, a sulphoxide-containing metabolite of BOF-4272) and that M-4 is mainly excreted in urine and possibly also in bile, with subsequent conversion to M-3 by the intestinal flora. It is expected that the biotransformation of BOF-4272 would be similar in healthy human volunteers.     

Metabolic studies of formestane in horses

Formestane (4‐hydroxyandrost‐4‐ene‐3,17‐dione) is an irreversible steroidal aromatase inhibitor with reported abuse in human sports. In 2011, our laboratory identified the presence of formestane in a horse urine sample from an overseas jurisdiction. This was the first reported case of formestane in a racehorse. The metabolism of formestane in humans has been reported previously; however, little is known about its metabolic fate in horses. This paper describes the in vitro and in vivo metabolic studies of formestane in horses, with the objective of identifying the target metabolite with the longest detection time for controlling formestane abuse. In vitro metabolic studies of formestane were performed using homogenized horse liver. Seven in vitro metabolites, namely 4‐hydroxytestosterone (M1), 3β,4α‐dihydroxy‐5β‐androstan‐17‐one (M2a), 3β,4β‐dihydroxy‐5β‐androstan‐17‐one (M2b), 3β,4α‐dihydroxy‐5α‐androstan‐17‐one (M2c), androst‐4‐ene‐3α,4,17β‐triol (M3a), androst‐4‐ene‐3β,4,17β‐triol (M3b), and 5β‐androstane‐3β,4β,17β‐triol (M4) were identified. For the in vivo studies, two thoroughbred geldings were each administered with 800 mg of formestane (32 capsules of Formadex) by stomach tubing. The results revealed that the parent drug and seven metabolites were detected in post‐administration urine. The six in vitro metabolites (M1, M2a, M2b, M2c, M3a, and M3b) identified earlier were all detected in post‐administration urine samples. In addition, 3α,4α‐dihydroxy‐5α‐androstan‐17‐one (M2d), a stereoisomer of M2a/M2b/M2c, was also identified. This study has shown that the detection of formestane administration would be best achieved by monitoring 4‐hydroxytestosterone (M1) in the glucuronide‐conjugated fraction. M1 could be detected for up to 34 h post‐administration. In blood samples, the parent drug could be detected for up to 34 h post administration. Copyright © 2013 John Wiley & Sons, Ltd.     

Pharmacokinetics and metabolism of pemafibrate,a novel selective peroxisome proliferator‐activated receptor‐alpha modulator,in rats and monkeys

The metabolic profiles and pharmacokinetics of pemafibrate, a novel selective peroxisome proliferator activated receptor‐alpha modulator currently launched as an antidyslipidemic drug, were investigated in vitro using hepatocytes from rats, monkeys and humans and in vivo in rats and monkeys. Hepatocytes from rats, monkeys and humans all biotransformed pemafibrate to its demethylated form (M1). The bioavailabilities of pemafibrate in Sprague–Dawley rats and cynomolgus monkeys were 15% and 87%, respectively, after a single oral administration of pemafibrate (1 mg/kg). In rat plasma, unmetabolized pemafibrate was the major form, accounting for 29% of the area under the curve (AUC) of total radioactivity. In monkey plasma, in contrast, the major circulating metabolites were M2/3 (dearylated/dicarboxylic acid forms, 15%), M4 (N‐dealkylated form, 21%) and M5 (benzylic oxidative form, 9%), but pemafibrate was the notable minor form (3%). These results, in combination with the reported findings in humans, suggest that the metabolite profile of pemafibrate in plasma was different for rats and monkeys, and that monkeys could be a suitable animal model for further pharmacokinetic studies of pemafibrate in humans.     

Urinary Metabolites of Rifabutin,a New Antimycobacterial Agent,in Human Volunteers

1. Metabolites of the antimycobacterial agent 4-deoxo-3,4-[2-spiro-(N-isobutyl-4-piperidyl)]-(1H)-imidazo-(2,5-dihydro)-rifamycin S (rifabutin) were isolated from human urine after administration of a single oral dose of the drug. Some of these metabolites were identified by direct inlet mass spectrometry, ¹H-n.m.r. spectrometry and, in two cases, by chromatographic comparison with reference compounds.

2. Unchanged drug, 25-O-deacetyl rifabutin and four other metabolites were identifed in human urine. 25-O-Deacetyl rifabutin was the main urinary metabolite, other metabolites were characterized as oxidized, and oxidized-deacetylated derivatives.

3. Routes of metabolic transformation were: (a) deacetylation at position 25, (b) oxidation of methyl groups 31 or 32 or at the piperidine nitrogen, and (c) combination of these.     

人胆汁中罗红霉素代谢产物的研究

目的：研究人胆汁中罗红霉素的代谢转化产物。方法：采用高效液相色谱-离子阱质谱法,对患者po罗红霉素后的胆汁样品进行了分析。结果：发现了13个代谢产物,分别为罗红霉素的(9Z)-异构体及其(9E)-,(9Z)-N-去甲基和N-双去甲基衍生物和(9E)-及(9Z)-脱克拉定糖衍生物,(9E)-和(9Z)-红霉素肟及其(9E)-和(9Z)-N-去甲基及N-双去甲基衍生物,其中9种为新发现的代谢物。结论：罗红霉素及其代谢物均可在体内发生几何异构化。