A preliminary multi-stable-isotopic evaluation of three synthetic pathways of Topiramate.

As a preliminary study of the utility of the natural stable-isotopic differentiation of batch samples produced by different synthetic pathways, multi-stable-isotopic analyses (delta(13)C, delta(15)N, delta(18)O, deltaD) of 53 samples of the antiepileptic drug, Topiramate, produced by three different synthetic pathways (designated "A," "B," "C") were performed. From the outset, we note that there are two fundamental variables that determine the stable-isotopic composition of materials-the stable-isotopic composition of the reagents and starting intermediates, and the isotope fractionation that occurs during manufacture of the product. In this study, the stable-isotopic composition of the raw materials was not controlled and we report here data obtained for a suite of samples that was produced by three synthetic pathways. Graphical examination of these data reveals marked data clustering by synthetic pathway, though in some cases with some overlapping values within standard errors. In general, the isotopic composition of Topiramate from the A and B pathways is distinct from the C pathway. The isotopic data from the A and B pathways typically abut each other, sometimes partially overlapping. The deuterium/hydrogen- (deltaD) and oxygen (delta(18)O) isotopic compositions are each significantly linearly related with the paired carbon (delta(13)C) isotopic composition indicating possible isotopic end-members for the raw materials of the present sample suite. Given that H and O typically derive from meteoric water, the linear correlations with delta(13)C indicate that a mixture of carbon sources (viz., perhaps terrestrial C3 photosynthetic organic carbon and marine C3 organic carbon) were used in the production of the batches tested. If the H and O analyzed were derived from meteoric water, then an elementary comparison of the span of the deltaD (DeltadeltaD = 54.6 +/- 2.1 per thousand) and of the delta(18)O (Deltadelta(18)O = 4.71 +/- 0.26 per thousand) values in the Topiramate samples to that of the global isotopic gradients indicates that the water retained in the samples spanned from as much as 11 degrees of latitude (or, approximately 760 statute miles North-to-South). The present isotope results (delta(13)C, delta(15)N, delta(18)O, deltaD) form an initial database against which future samples can be compared to infer specific synthetic pathways. It is clear that to perform a rigorous test of the variables controlling the stable-isotopic composition of pharmaceutical materials that both the stable-isotopic composition of the starting materials and synthetic isotope fractionation must be controlled in future studies.

Minimization and management of wastes from biomedical research.

Several committees were established by the National Association of Physicians for the Environment to investigate and report on various topics at the National Leadership Conference on Biomedical Research and the Environment held at the 1--2 November 1999 at the National Institutes of Health in Bethesda, Maryland. This is the report of the Committee on Minimization and Management of Wastes from Biomedical Research. Biomedical research facilities contribute a small fraction of the total amount of wastes generated in the United States, and the rate of generation appears to be decreasing. Significant reductions in generation of hazardous, radioactive, and mixed wastes have recently been reported, even at facilities with rapidly expanding research programs. Changes in the focus of research, improvements in laboratory techniques, and greater emphasis on waste minimization (volume and toxicity reduction) explain the declining trend in generation. The potential for uncontrolled releases of wastes from biomedical research facilities and adverse impacts on the general environment from these wastes appears to be low. Wastes are subject to numerous regulatory requirements and are contained and managed in a manner protective of the environment. Most biohazardous agents, chemicals, and radionuclides that find significant use in research are not likely to be persistent, bioaccumulative, or toxic if they are released. Today, the primary motivations for the ongoing efforts by facilities to improve minimization and management of wastes are regulatory compliance and avoidance of the high disposal costs and liabilities associated with generation of regulated wastes. The committee concluded that there was no evidence suggesting that the anticipated increases in biomedical research will significantly increase generation of hazardous wastes or have adverse impacts on the general environment. This conclusion assumes the positive, countervailing trends of enhanced pollution prevention efforts by facilities and reductions in waste generation resulting from improvements in research methods will continue.

Separation of fatty acid ester and amide enantiomers by high-performance liquid chromatography on chiral stationary phases.

The enantiomeric resolution of a series of chiral fatty acid epoxide and alpha-substituted palmitic acid analogues was examined by high-performance liquid chromatography on chiral stationary phases. The compounds were chromatographed as ester or amide derivatives on commercially available stationary phases that consisted of (R)-N-(3,5-dinitrobenzoyl)phenylglycine either covalently or ionically bonded to aminopropylsilica gel. Factors affecting separation included hydrocarbon chain length of the fatty acid, the type of substituents attached to the chiral center, the type of derivative, and column temperature. Effects of sample size, mobile phase composition, column type, and flow-rate on the resolution and separation factor values were also explored.

A high-performance liquid chromatographic method for the enantiomeric analysis of the enzymatically synthesized coenzyme A ester of 2-tetradecylglycidic acid.

The enantiomeric composition of an enzymatically synthesized sample of the coenzyme A ester of 2-tetradecylglycidic acid (TDGA-CoA) was determined by the use of high-performance liquid chromatography with a chiral stationary phase. The stationary phase was commercially available and consisted of (R)-N-(3,5-dinitrobenzoyl)phenylglycine covalently bonded to aminopropyl silica gel. Analysis was performed using the phenacyl derivative of 2-tetradecylglycidic acid (TDGA), obtained by mild hydrolysis of the TDGA-CoA followed by reaction of the extracted TDGA with phenacyl chloride. Chromatography showed the enantiomeric purity of TDGA-CoA, synthesized in a rat liver microsomal enzyme mixture over a 2-h period, to be a 15.6:1 ratio of the R:S enantiomers (88% ee). The result demonstrates the stereoselectivity of the long-chain fatty acid-coenzyme A synthetase for chiral fatty acid epoxide, TDGA.

Identification of 2-tetradecylglycidyl coenzyme A as the active form of methyl 2-tetradecylglycidate (methyl palmoxirate) and its characterization as an irreversible, active site-directed inhibitor of carnitine palmitoyltransferase A in isolated rat liver mitochondria.

Methyl-2-tetradecylglycidic acid (MeTDGA) has been hypothesized to inhibit fatty acid oxidation by irreversible, active site-directed inactivation of carnitine palmitoyltransferase A after being converted to TDGA-CoA. Using synthetic TDGA-CoA, this hypothesis has been confirmed. Assessing enzyme inhibition in an isolated rat liver mitochondrial system, TDGA-CoA (synthetic or enzyme prepared) was more potent than TDGA or MeTDGA and retained activity in the absence of CoA or Mg2+-ATP. It inhibited palmitoyl-CoA but not palmitoyl carnitine oxidation. Enzyme inactivation was exponential, stereospecific, and fast (t0.5 = 38.5 s with 100 nM (R)-TDGA-CoA). TDGA-CoA was identified as a complexing type irreversible inhibitor (Ki approximately 0.27 microM) by the double reciprocal relationship between the pseudo-first order inactivation rate and its concentration, by the inverse dependence of the second order rate constant on its concentration, and by the independence of the first order rate from the enzyme concentration. Palmitoyl-CoA, CoA, and malonyl-CoA protected the enzyme, while L-carnitine and palmitoyl-L-carnitine were without effect. [3-14C] TDGA-CoA labeled a protein, Mr = 90,000, with a time course which paralleled that of enzyme inhibition; maximum specific binding was 16 pmol/mg of mitochondrial protein.

The metabolism of zomepirac sodium. II. Isolation and identification of the urinary metabolites in rat, mouse, rhesus monkey, and man.

The metabolism of the oral analgesic agent, zomepirac sodium, sodium 5-(4-chlorobenzoyl)-1,4-dimethyl-1 H-pyrrole-2-acetate dihydrate, was studied in healthy male humans, rhesus monkeys, Wistar rats, and Swiss mice. The major urinary metabolites of zomepirac (Z) (80--95% of the dose) in these species were identified on the basis of a combination of chromatographic and spectroscopic data. Z was present as a major product in all species. Hydroxyzomepirac (HMZ) was a major component in rat and mouse, but a minor one in man, and it was absent in the monkey. 4-Chlorobenzoic acid (CBA) was identified as a major metabolite in rat (present as conjugates) and mouse and a minor one in monkey and man. Zomepirac glucuronide (ZG) was present as the major metabolite in man, monkey, and mouse, and present at trace levels in the rat. 4-Chlorohippuric acid, the glycine conjugate of CBA, was found in trace amounts only in the monkey. Thus, the metabolism of zomepirac in man and monkey is mainly characterized by glucuronide conjugation. The rat metabolizes zomepirac, mainly by oxidative pathways, to give HMZ and CBA. The mouse shows a balance of conjugation and oxidative pathways.