Synthesis and metabolism of the first thia-bilirubin

A symmetrical C(10)-thiabilirubin analogue, 8,12-bis(2-carboxyethyl)-2,3,17,18-tetraethyl-7,13-dimethyl-10-thia-(21H,23H,24H)-bilin-1,19-dione (1), was synthesized from 8-(2-carboxyethyl)-2,3-diethyl-7-methyl-10H-dipyrrin-1-one in one step by reaction with sulfur dichloride. The thia-rubin exhibited the expected IR, UV-vis, and NMR spectroscopic properties, which are rather similar to those of mesobilirubin-XIIIalpha. Like bilirubin and mesobilirubin, 1 adopts an intramolecularly hydrogen-bonded conformation, shaped like a ridge-tile but with a steeper pitch. The longer C-S bond lengths and smaller bond angles at C-S-C, as compared to C-CH(2)-C, lead to an interplanar angle between the two dipyrrinones of only 74 degrees -or considerably less than that of bilirubin (approximately 100 degrees). On normal- and reversed-phase chromatography, 1 is substantially less polar than bilirubin. Despite this conformational distortion, 1 is metabolized in normal rats to acyl glucuronides, which are secreted into bile. In mutant (Gunn) rats lacking bilirubin glucuronosyl transferase, 1 (like bilirubin) was not excreted in bile.     

Synthesis and spectroscopic properties of a new class of strongly fluorescent dipyrrinones

A new, highly fluorescent (Phi(F) > or = 0.8) chromophore has been synthesized in one step from dipyrrinones by reaction with N,N-carbonyldiimidazole to form the 3H,5H-dipyrrolo[1,2-c:2',1'-f]pyrimidine-3,5-dione nucleus.     

A new class of linear tetrapyrroles: acetylenic 10,10a-didehydro-10a-homobilirubins

Novel bilirubin analogues with dipyrrinones conjoined to an acetylene rather than a methylene group were synthesized and examined spectroscopically. Despite the increased separation of the dipyrrinones forced by replacing a -CH(2)- by a -C(triple bond)C- unit, molecular dynamics calculations show that, like bilirubin, they may still engage in intramolecular hydrogen bonding to carboxylic acid groups when the propionic acid chains are slightly lengthened, e.g., butanoic acids. Unlike bilirubin, however, which is bent in the middle and has a ridge-tile shape, the acetylene orients the attached dipyrrinones along a linear path, and intramolecular hydrogen bonding preserves a twisted linear molecular shape. The extended planes of the dipyrrinones intersect along the -C(triple bond)C- axis at an angle of 136 degrees for the conformation stabilized by intramolecular hydrogen bonding in the bis-butyric acid rubin (1b). With shorter acid chains (propionic), only one CO(2)H can engage an opposing dipyrrinone in intramolecular hydrogen bonding, and in this energy-minimum conformation of the linear pigment 1a, the intersection of the extended planes of the dipyrrinones has an angle of 171 degrees. Spectroscopic evidence for such linearized and twisted structures was found in the pigments' NMR spectral data and their exciton UV-vis and induced circular dichroism spectra.     

Synthesis, properties, and hepatic metabolism of strongly fluorescent fluorodipyrrinones

From non-fluorescent 8-H fluorophenyldipyrrinones, highly fluorescent (?_F 0.4-0.6) analogs have been synthesized by reaction with 1,1′-carbonyldiimidazole to bridge the dipyrrinone nitrogens and form an N,N′-carbonyldipyrrinone (3H,5H-dipyrrolo[1,2-c:2′,1′-f]pyrimidine-3,5-dione). Amphiphilic, water-soluble 8-sulfonic acid derivatives are then obtained by reaction with concd H₂SO₄. The resulting fluorinated and sulfonated N,N′-carbonyl-bridged dipyrrinones, isolated as their sodium salts, are potential cholephilic fluorescence and ¹⁹F MRI imaging agents for use in probing liver and biliary metabolism. After intravenous injection in the rat they were excreted rapidly and largely unchanged in bile. ¹⁹F NMR spectroscopy of a pentafluorophenyl-tosylpyrrolinone synthetic precursor exhibited rarely seen diastereotopicity.     

Pharmacokinetics and excretion study of bergenin and its phase II metabolite in rats by liquid chromatography tandem mass spectrometry

A sensitive and selective liquid chromatographic–tandem mass spectrometric (LC–MS/MS) method for the determination of bergenin and its phase II metabolite in rat plasma, bile and urine has been developed. Biological samples were pretreated with protein precipitation extraction procedure and enzymatic hydrolysis method was used for converting glucuronide metabolite to its free form bergenin. Detection and quantitation were performed by MS/MS using electrospray ionization and multiple reaction monitoring. Negative electrospray ionization was employed as the ionization source. Sulfamethoxazole was used as the internal standard. The separation was performed on a reverse‐phase C₁₈ (250 × 4.6 mm, 5 μm) column with gradient elution consisting of methanol and 0.5% aqueous formic acid. The concentrations of bergenin in all biological samples were in accordance with the requirements of validation of the method. After oral administration of 12 mg/kg of the prototype drug, bergenin and its glucuronide metabolite were determined in plasma, bile and urine. Bergenin in bile was completely excreted in 24 h, and the main excreted amount of bergenin was 97.67% in the first 12 h. The drug recovery in bile within 24 h was 8.97%. In urine, the main excreted amount of bergenin was 95.69% in the first 24 h, and the drug recovery within 24 h was <22.34%. Total recovery of bergenin and its glucuronide metabolite was about 52.51% (20.31% in bile within 24 h, 32.20% in urine within 48 h). The validated method was successfully applied to pharmacokinetic and excretion studies of bergenin.     

Investigation of the metabolic fate of 2-, 3- and 4-bromobenzoic acids in bile-duct-cannulated rats by inductively coupled plasma mass spectrometry and high-performance liquid chromatography/inductively coupled plasma mass spectrometry/electrospray mass spectrometry

Inductively coupled plasma mass spectrometry (ICPMS) has been used to determine the rate and routes of excretion of bromine following the intraperitoneal administration (50 mg kg(-1)) of 2-, 3- and 4-bromobenzoic acids to male bile-duct-cannulated rats. Analysis of urine and bile for (79/81)Br using ICPMS showed that all three bromobenzoic acids were rapidly excreted (82-98%) within 48 h of dosing, primarily via the urine. High-performance liquid chromatography/inductively coupled plasma mass spectrometry (HPLC/ICPMS) was then used to obtain metabolite profiles for bile and urine. These profiles revealed that extensive metabolism had taken place, with the unchanged bromobenzoic acids forming a minor part of the total of compound-related material detected. Concomitant MS studies, supplemented by alkaline hydrolysis, enabled the identification of the major metabolite of all three of the bromobenzoic acids as a glycine conjugate. Ester glucuronide conjugates were also identified, but formed only a small proportion of total.     

稀土对大鼠代谢产物影响的核磁共振研究

以高场核磁共振技术为研究手段,通过分析腹腔注射０．２、２、１０、２０ｍｇ／ｋｇ体重剂量的Ｌａ（ＮＯ３）３后大鼠尿液中代谢物浓度、物种的变化,研究了稀土化合物在动物体内的作用情况,结果表明,稀土的引入使动物肾脏和肝脏都受到一定程度的损伤,并在代谢物中挑选出了合适的ＮＭＲ ｍａｒｋｅｒｓ,其变化可以反映稀土离子作用后大鼠的异常代谢。     

Metabolic fate of timepidium bromide (SA-504)--Unstable metabolities in the rats

The colored substances excreted in bile or urine have bee investigated after adminstration of a high dose of SQ-504 to rats. A reddish-violet colored substance and a bluish-violet colored substance were dominant. Their chemical structures were not assigned because of their small quantity and instability. It was recognized that the colored substances were metabolites of SA-504 from the studies with 3H and 14C labelled SA-504 and the derivatives of SA-504.     

Novel Linear Tetrapyrroles: Hydrogen Bonding in Diacetylenic Bilirubins

Summary. Bilirubin congeners with dipyrrinones conjoined to a diaceteylene unit (–CC–CC–) rather than to –CH₂– were synthesized and examined spectroscopically. This new class of rubrified linear tetrapyrroles cannot easily fold or bend in the middle, but the dipyrrinones can rotate independently about the diacetylene unit. Thus, unlike bilirubin, which is bent in the middle and has a ridge-tile shape, the diacetylene unit orients the attached dipyrrinones along a linear path, and intramolecular hydrogen bonding between the dipyrrinones and opposing carboxylic acids preserves a twisted linear molecular shape when the usual propionic acids are replaced by hexanoic. In a bis-hexanoic acid rubin, the extended planes of the dipyrrinones intersect along the –(CC)₂– axis at an angle of 102° for the conformation stabilized by intramolecular hydrogen bonding. With propionic acid chains, however, neither CO₂H can engage an opposing dipyrrinone in intramolecular hydrogen bonding, and the energy-minimum conformation of this linear pigment, shows nearly co-planar dipyrrinones, with an intersection of an angle of 180° of the extended planes of the dipyrrinones. Spectroscopic evidence for such linearized and twisted (bis-hexanoic) and planar (bis-propionic) structures comes from the pigments NMR spectral data and their exciton UV-Vis and induced circular dichroism spectra.     

Biliary excretion of metabolites of baicalin and baicalein in rats

Biliary excretion of metabolites of baicalin, present in Scutellariae Radix, was investigated using rats. The bile of rats administered baicalin orally was shown to contain five major metabolites, which were identified as baicalein 6-O-beta-glucopyranuronoside (M1), 6-O-methyl-baicalein 7-O-beta-glucopyranuronoside (oroxylin A 7-O-beta-glucuronide (M2], baicalein 7-O-beta-glucopyranuronoside (M3), 6-O-beta-glucopyranuronosyl- baicalein 7-O-sulfate (M4), and baicalein 6,7-di-O-beta-glucopyranuronoside (M5) on the basis of chemical and spectroscopic evidence. The bile of rats treated with baicalein also contained the above metabolites. Slower biliary excretion of the metabolites after baicalin administration suggested that it was absorbed as baicalein after hydrolysis in the gastrointestinal tract. The total cumulative amounts of the five metabolites excreted in the bile during 30 h after oral administration of baicalin and that of baicalein were approximately 54% and 40% of the doses, respectively. In addition the bilary metabolites of both drugs were shown to be mainly composed of M5 and M4, which have high polarity and large molecular weight.     

Isolation and purification of uremic middle molecules by multi-step liquid chromatography

Isolation and comparison of uremic sera and urine and normal sera and urine were performed by gel permeation chromatography, anion exchange chromatography and re-versed-phase high performance liquid chromatography. Two uremic middle molecular fractions (A and B) were obtained from uremic sera and urine and normal urine by gel permeation chromatography, but not from normal sera. The anion exchange chromatographic results of fraction A from different origins demonstrate that subfraction A-3 could be excreted in urine by healthy subject, but accumulated in uremic serum for renal failure of patient with uremia. After desalinization subfraction A-3 was analyzed by MALDI-TOF-MS. The results show that subfraction A-3 consists of six compounds with molecular weight 839, 873, 1007.94, 1106, 1680 and 2015 respectively. Finally, by reversed-phase high performance liquid chromatography, subfraction A-3 was further resolved into six independent fractions. Thus, the isolation and purification of six middle molecular c     

Nickel Complexes Bearing Bidentate Schiff Base as Ethylene Oligomerization Catalysts

Several nickel complexes [N,N]NiBr2, in which IN,N] indicates bidentate nitrogen-containing ligands (1: [N,N]=N-(2,6-diisopropylphenyl)pyridine-2-carboxaldimine (Cl8H22N2); 2: N-(2,6-diisopropylphenyl)-6-methylpyridine-2-carboxaldimine (C19H24N2); 3: N-(2,4,6-trimethylphenyl)pyridine-2-carboxaldimine(Cl5Hl6N2); 4: N-(2,4,6-trimethylphenyl)-6-methylpyridine-2-carboxaldlmlne (Cl6Hl8N2) were synthesized. Some of the nickel complexes exhibit high activity for ethylene oligomerization in the presence of an organoaluminum activator. The main factor affecting the activity and the structure of oligomers is the steric effect of substituents on [N,N] ligands. Methylaluminoxane (MAO) -activated catalysts showed higher activities and produced oligomers with higher molecular weight than Et2AlCl-activated ones. The oligomerization in toluene rather than hexane results in much higher activity, and the oligomers produced in toluene have relatively high molecular weight. With activation of MAO or Et2AlCl,the [N,N]NiBr2 system tended to produce highly branched oligomers with low α-olefin content, but the α-olefin content could be increased by changing the reaction conditions.     

Studies on the metabolism of gomisin A (TJN-101). II. Structure determination of biliary and urinary metabolites in rat

After oral administration of gomisin A (1) to rats, the bile and urine were collected and treated with beta-glucuronidase and arylsulfatase. Seven metabolites, met B (2), met A-III (3), met E (4), met D (5), met F (6), met G (7), and met H (8) were isolated from the bile treated with the enzymes. Eight metabolites 2-8, and met A-II (9) were isolated from the urine treated with the enzymes. A major metabolite 2, and two minor metabolites 3 and 9 were identified as met B, met A-III, and met A-II, respectively, which are oxidative products of 1 formed by rat liver S9 mix. The structures of five new metabolites 4-7, and 8 were determined on the basis of chemical and spectral studies.     

In vivo copper-mediated free radical production: an ESR spin-trapping study

Copper has been suggested to facilitate oxidative tissue injury through a free radical-mediated pathway analogous to the Fenton reaction. By applying the electron spin resonance (ESR) spin-trapping technique, evidence for hydroxyl radical formation in vivo was obtained in rats treated simultaneously with copper and ascorbic acid or paraquat. A secondary radical spin-trapping technique was used in which the hydroxyl radical formed the methyl radical upon reaction with dimethylsulfoxide. The methyl radical was then detected by ESR spectroscopy as its adduct with the spin trap phenyl-N-t-butyl- nitrone (PBN). In contrast, lipid derived radical was detected in vivo in copper-challenged, vitamin E and selenium-deficient rats. These findings support the proposal that dietary selenium and vitamin E can protect against lipid peroxidation and copper toxicity. Since copper excreted into the bile from treated animals is expected to be maintained in the Cu(I) state (by ascorbic acid or glutathione), a chelating agent that would redox-stablilize it in the Cu(I) state was used to prevent ex vivo redox chemistry. Bile samples were collected directly into solutions of bathocuproinedisulfonic acid, a Cu(I)-stabilizing agent, and 2,2'-dipyridyl, a Fe(II)-stabilizing agent. If these precautions were not taken, radical adducts generated ex vivo could be mistaken for radical adducts produced in vivo and excreted into the bile.     

硝酸镥急性毒性的体液核磁共振氢谱研究

采用现代核磁共振技术,通过分析灌胃给药0．01、0．05、0．2、2、10和100ms／kg剂量Lu(NO3)3 24h内大鼠尿液及24h后大鼠血清的核磁共振氢谱(^1HNMR),由体液中内源性代谢物浓度的变化研究了稀土化合物在动物体内急性毒性。较高剂量组体液中的氨基酸、尿囊素、柠檬酸、氮氧三甲胺和肌酸酐等重要内源性代谢物的核磁共振谱峰强度发生了明显的变化,说明动物体内的代谢物出现异常：高剂量的稀土的引入可能使动物肾脏和肝脏均受到损害,且受损程度随稀土剂量的增高而渐趋严重。     

Evaluation of 99mTc-HIDA complex as a cholescintigraphic agent (author's transl)

In the reaction labeling N-(2,6-dimethylphenylcarbamoylmethyl) iminodiacetic acid (HIDA) with 99mTc, several complexes with different chemical characteristics were observed to occur with slight changes in the labeling conditions. Among these complexes, a complex detected in the bile of rats was limited to one complex, named as complex II. The preparation method of 99mTc-HIDA complex II and the exchange reaction between this complex and penicillamine indicate that 99mTc is coordinated with HIDA as low-hydrolyzed 99mTc in this complex. This complex is excreted rapidly through the bile and within 1 hr, about 65% of the total activity injected is recovered from bile in rats. The organ distribution of this complex was studied in mice by radioassay and in rabbits by scintillation camera and, in both cases, the radioactivity was accumulated in the gallbladder. These results suggest that the 99mTc chemical state, low-hydrolyzed state, relates to the bile excretion behavior of this complex, a potentially useful cholescintigraphic agent.     

Targeting of liposomes surface-modified with glycyrrhizin to the liver. I. Preparation and biological disposition

We consider glycyrrhizin to be a new ligand for liposomes to the liver because it is known that about 80% of glycyrrhizin is excreted into the bile after intravenous administration in rats. In order to modify the liposomal surface with glycyrrhizin, 30-stearyl glycyrrhizin (GLOSt), one of the lipophilic glycyrrhizin derivatives, was synthesized. The structure of this new compound was identified by nuclear magnetic resonance (NMR), infrared (IR) and mass spectra (MS). Sonicated liposomes were prepared from hydrogenated egg phosphatidylcholine-cholesterol-GLOSt or dicetyl phosphate (DCP) (4:4:1) and were labelled with [3H]inulin as an aqueous marker. It was confirmed by measuring the encapsulation efficiencies and the mean diameters that GLOSt-containing sonicated liposomes (GLOSt-SUV) were SUV-type as well as DCP-containing control liposomes (control-SUV). Four hours after intravenous injection into rats at a dose of 90 mumol as total lipid per kg of rat body weight, GLOSt-SUV showed 4-fold more accumulation (42.4%) in the liver than control-SUV. Therefore, glycyrrhizin is considered to be a useful new ligand on liposomes for targeting to the liver.     

Speciation of metabolites of selenate in rats by HPLC-ICP-MS

The metabolic pathway for and metabolites of selenium (Se) administered intravenously to rats in the form of selenate at a dose of 0.3 mg Se kg-1 body weight were studied by speciating Se in the bloodstream, liver and urine by HPLC-inductively coupled argon plasma mass spectrometry. Selenate was not taken up by red blood cells (RBCs) and disappeared from the bloodstream much faster than selenite, without any change in its chemical form before it disappeared from the plasma. Selenium excreted into the urine after the administration of selenate showed different patterns from those of selenite in both amounts and chemical forms. With the selenate group, the concentration of Se in urine was highest at 0-6 h and the chemical species of Se was selenate at 0-6 h; thereafter a monomethylselenol-related Se compound (MMSe*) and trimethylselenonium ions (TMSe) appeared, selenate not being excreted after 6 h. On the other hand, in the selenite group, the concentration of Se peaked at 6-12 h, and the chemical species of Se were MMSe* and TMSe. Selenate was reduced in vitro on incubation in either a liver homogenate or supernatant fraction, although much more slowly than in the whole body. Selenate was not reduced by glutathione or dithiothreitol. The results suggest that in contrast to selenite, which is taken up by and reduced in RBCs, and then transferred to the liver, approximately 20% of the selenate administered to rats was excreted into the urine without any change in its chemical form with the present dose, and the major portion of selenate was taken up by the liver, reduced and then utilized for the synthesis of selenoproteins or excreted into the urine after being methylated.     

Absorption and excretion of suprofen in both sexes of rats, guinea pigs, and rabbits

DL-2-(4-2-Thienylcarbonyl)phenyl)propionic acid (suprofen) was rapidly absorbed in both sexes of rats, guinea pigs, and rabbits after oral administration. Blood levels after a single dose of 2 mg/kg 3H-suprofen in all the animals reached maxima within 15 min, and elimination of the 3H from blood was rapid; the radioactivity was mostly excreted in the urine and feces within 24 h after dosing.     

尿毒症中分子毒物的分离及飞行时间质谱分析

尿毒症被认为是因为患者肾衰而毒素在体内滞留所致^[1]。1972年Babb等^[2]提出“中分子假说”,认为分子量在300－2000范围内的中等分子量的物质是尿毒症的主要毒性物质。从此,人们作了大量的努力去分离和鉴定尿毒症中分子毒物。然而尿毒症中分子毒物的成分极其复杂^[3],从设定的中分子组分中分离得到的大都是些分子量小于800的小分子物质^[4]。因而对中分子假说一直存在争议^[5].我们对尿毒症患者及正常人的血清和尿液进行凝胶色谱分离,从尿毒症血清和尿液及正常人尿液中得到两个中分子峰A,B。将不同来源的A峰中的分子毒物进行离子交换色谱的分离和比较,得到了仅存在于尿毒症血清和正常人尿液的A－3亚峰,经脱盐和飞行时间质谱分析,确定了该组分内含有分子分别为839．69,1007．94,2015．16,16,873．69,1106．67和1680．28的6种化合物。