Frederick J. Dicarlo

The absorption and biotransformation of glyceryl trinitrate-1,3-14C by rats

Abstract The metabolism of 14 C-labeled glyceryl trinitrate was studied in the rat. Absorption, tissue distribution and elimination were followed after administering a single dose by gavage. Thin-layer chromatography and radio-scanning methods were employed to assay urinary drug metabolites, including the isomeric glyceryl dinitrates and glyceryl monoitrates. It was found that glyceryl trinitrate was absorbed and transformed very rapidly. The major products were carbon dioxide, urinary glycerol, glyceryl nitrates, organic acids and some unidentified tissue components which were also labeled with 14 C.

Identification and assay of isomeric 14C-glyceryl nitrates

Abstract A method was developed for the differentiation of glyceryl-1,2-dinitrate from glyceryl-1,3-dinitrate and glyceryl-1-nitrate from glyceryl-2-nitrate. Using thin-layer chromatography and 14C labeling, these compounds can be assayed quantitatively and simultaneously in the presence of glyceryl trinitrate and glycerol.

Prazepam metabolism by man

The absorption, excretion, and biotransformation of 14C‐labeled prazepam were studied in man. Slow, sustained absorption followed the administration of a single oral dose. The peak level of the blood radioactivity was observed after 6 hours. Clearance from the blood was also slow, particularly with respect to the unconjugated forms of the drug. Unlike diazepam, the major phase 1 reaction for prazepam was hydroxylation at carbon‐3 rather than dealkylation. Initially, the principal urinary metabolite was 3‐hydroxyprazepam glucuronide. Oxazepam glucuronide was excreted in increasing quantities over the 48 hour study period so that its total excretion approached that of 3 ‐hydroxyprazepam glucuronide. No unaltered prazepam was detected in the urine and the level of desalkylprazepam was low. Several unidentified radioactive glucuronides and sulfates were also excreted in the urine.

Nitroglycerin biotransformation by rat blood serum

Abstract The degradation of 14 C-labeled glyceryl trinitrate by rat blood serum was investigated. Attention was focused upon the first de-esterification which yielded inorganic nitrite and the two isomeric glyceryl dinitrates. Cleavage of the nitrate group at carbon-2 was favored 4-fold over attack upon each terminal nitrate. The conversion proceeded optimally at approximately pH 7–8 and within the temperature range of 50–57°. Iodoacetamide and p -chloromercuribenzoate inhibited the ability of rat serum to transform nitroglycerin. Serum activity was not lost by dialysis. The data are interpreted as indicating that the de-esterification of nitroglycerin by serum is enzymatic and involves the reduction of organic nitrate to organic nitrite followed by the hydrolysis of nitrite ester to inorganic nitrite. The V max of the unpurified rat serum showed it to be more potent than the hog liver organic nitrate reductase described previously. Unlike the hog liver enzyme, the serum reductase does not require reduced glutathione. Lacking this requirement, the serum system is also free of dependence upon TPNH for the function of glutathione reductase.

Biotransformation of the methylenedioxy moeity of oxolinic acid in man

Abstract A new drug metabolite was isolated as an aglycon from the urine of men who ingested a single dose of 14C-labeled oxolinic acid. The aglycon responded to phenol tests and yielded a mass spectrum which indicated a molecular weight of 263, two higher than the parent drug. From ultraviolet, infrared and mass spectral data on the new compound and related synthetic compounds, it was concluded to be either 1-ethyl-1,4-dihydro-6-hydroxy-7-methoxy-4-oxo-3-quinoline carboxylic acid or the corresponding 6-methoxy-7-hydroxy isomer. The latter structure was favored because the literature indicates preferential methylation of the more nucleophilic hydroxy of ring-substituted catechols. Authentic 1-ethyl-1,4-dihydro-6-methoxy-7-hydroxy—4-oxo-3-quinoline carboxylic acid was synthesized and found to be identical with the isolated aglycon.

BIOTRANSFORMATION OF PRAZEPAM IN MAN

The subjects were five healthy men between the ages of 28 and 55. Each subject swallowed a capsule containing 25 mg of prazepam labeled with “C at position 5 (indicated in above structure with an asterisk) so that his radioactive dose was 33 pc. Blood samples were withdrawn from each man a t 1, 2, 4, 6, 8, 10, 24, and 48 hours after treatment. Unconjugated compounds were collected from the blood by repeated extraction with ethyl acetate and were estimated by counting for “C by scintillation spectrometry. After removal of residual solvent, the extracted blood was incubated twice with 5,000 units of 8-glucuronidase at 3 7 O for 24 hours. Then the aglycones were extracted with ethyl acetate and estimated by scintillation spectrometry. FIGURE 1 shows the mean values for unconjugated drug metabolites and labeled glucuronides plotted in terms of microgram equivalents of prazepam per ml of blood. I t is evident that unconjugated drug and metabolites were predominant in the systemic circulation over the entire 48-hour study period. The slow increase in blood radioactivity following prazepam administration was more consistent with the intestinal binding of benzodiazepins de-

The pharmacodynamics and biotransformation of pentaerythritol trinitrate in man

Pentaerythritol trinitrate (PE‐trinitrate), a metabolite in man of pentaerythritol tetranitrate (PETN), has been found to possess considerably greater vasodilator activity than its parent drug. Pharmacokinetics and metabolism of PE‐trinitrate were studied after single sublingual and oral doses of 14C‐PE‐trinitrate given in clinical dosage form. Drug absorption rate constants obtained from blood concentrations of drug radioactivity showed that absorption was rapid with both modes of administration. Metabolism and elimination after both dosage modes were nearly identical. The drug was not found in urine or in blood except within a few minutes of administration. Urinary elimination of metabolites accounted for 92 per cent of the dose, with less than 2 per cent recovered in fecal excretion as pentaerythritol (PE). The principal urinary metabolites were PE (30 per cent) and PE‐mononitrate (69 per cent). Excretion of these metabolites was first order with half‐times of elimination of 10.5 and 7.3 hours, respectively. From a comparison of the pharmacokinetics and biotransformation of PE‐trinitrate with those previously observed for PETN in similar experimental conditions, it is suggested that the rates of absorption and intracellular accumulation at tissue sites of action are primary determinants of the pharmacological activity and relative potencies of the organic nitrates.

Pectic acid from the mucilage of coffee cherries

Abstract 1. 1. A polysaccharide fraction was isolated from the mucilaginous layer of coffee cherries. 2. 2. This purified fraction was found to contain 77.6% anhydrogalacturonic acid residues, and small amounts of arabinose, xylose galactose, and rhamnose. 3. 3. The sugars were removed by hydrolysis with dilute acid, and barium galacturonate was isolated in good yield from the sugar-free residue. 4. 4. Coffee mucilage fractions responded to acid and enzymatic hydrolyses in a manner very similar to citrus pectic acid.

Binding and Metabolism of Nitroglycerin by Rat Blood Plasma

Summary The ultrafiltration technique was employed to measure the extent of 14C-nitroglycerin binding by the proteins of rat blood plasma. Over the concentration range of 50-500 μg of nitroglycerin/ml of plasma, approximately 60% of the drug was bound. During the course of the binding experiments, nitroglycerin was metabolized to glyceryl dinitrates. Twice as much glyceryl-1, 3-dinitrate was formed as glyceryl-1, 2-dinitrate, indicating a strongly preferential attack upon the 2-position rather than upon the terminal positions. The metabolites were also bound by plasma proteins with glyceryl-1,2-dinitrate being held more extensively (about 60%) than glyceryl-1,3-dinitrate (35%).

Pentaerythritol trinitrate metabolism by the rat.

Abstract Rats were studied after being given a single dose of 14C-pentaerythritol trinitrate by gavage. The labeled components of the blood, urine and gastrointestinal tract were identified by thin-layer chromatography and assayed quantitatively by radioscanning. Pentaerythritol trinitrate was found to be absorbed and excreted rapidly by the rat. The drug metabolites were pentaerythritol, pentaerythritol mononitrate and pentaerythritol dinitrate. Comparisons of the data with the results of similar studies with pentaerythritol tetranitrate (PETN) and nitroglycerin showed that pentaerythritol trinitrate was absorbed much faster than PETN and almost as quickly as nitroglycerin, and that the urinary excretion of pentaerythritol trinitrate proceeded at the highest rate. Additionally, pentaerythritol trinitrate was the only one of the three drugs which passed intact into the urine.