Species differences in metabolism of panomifene, an analogue of tamoxifen.

In vitro metabolism of panomifene (E-1,2-diphenyl-1--4-(2-(2-hydroxyethyl-amino)-ethoxy)-phenyl--3,3,3- trifluoropropene), a novel antiestrogen against hormone dependent tumors, has been investigated using liver microsomes from mouse, rat, dog, and human. Hydroxylation and side chain modifications were the routes of panomifene metabolism. Microsomal biotransformation showed some qualitative similarities, but several differences were observed in the metabolic profiles of the four species tested. Seven metabolites were detected in the incubation mixtures analyzed by thin layer chromatography and autoradiography, although there was only one produced by all species that had lost the side chain. Among the side chain shortened metabolites, the compound that had lost the hydroxyethyl-amino group was formed by the microsomal system of rodents, whereas the one that had lost the hydroxyethyl group was detected in the incubation mixtures with rat, dog, and human microsomes. Three metabolites (M1, M3, and M4) were produced exclusively by the dog. The structure of M3 was identified by mass spectroscopy as 4-hydroxy-panomifene. Furthermore, human liver microsomes formed a metabolite (M8) that was not detectable in the mixtures with mouse, rat, or dog microsomes. Its structure is suspected to be an oxidized form of panomifene with a double bound in the side chain. The structure of panomifene is analogous to tamoxifen, an antiestrogen currently used as a therapeutic agent against breast cancer, and there are some similar routes in their metabolism. The main difference is that the rate of tamoxifen biotransformation seems faster than that of panomifene. On the other hand, 4-hydroxy-panomifene is produced by only dog, while 4-hydroxylated derivative is one of the main metabolites of tamoxifen that has potent antiestrogenic activity and is considered to be responsible for the formation of DNA-adducts.

Distinction of amino Acid enantiomers based on the basicity of their dimers.

Mixtures of several amino acid pairs, in all four chiral combinations, were studied. The protonated trimers (A(2)BH(+)) fragment, forming ABH(+) and A(2)H(+) dimers. Abundance ratios of these fragments were measured in the mass-analyzed ion kinetic energy spectra of the trimers. These were found to depend on the stereochemistry (homo- or heterochiral form) of the ABH(+) dimer. The results were evaluated using the kinetic method, and the chiral discrimination was related to a difference in gas-phase basicity (GB) between the homo- and the heterochiral dimers. Four amino acid pairs (proline-tryptophan, phenylalanine-alanine, phenylalanine-proline, and phenylalanine-valine) were studied. Chiral discriminations were observed in all cases, relating to 0.4-4 kJ/mol differences in GB. The technique described here can generally be used to study enantiomers by mass spectrometry and is capable of reliably distinguishing energy differences as small as 0.2 kJ/mol in cluster ions.

Characterization and differentiation of heterocyclic isomers. tandem mass spectrometry and molecular orbital calculations on 3-methylisoxazolo- and 2-methyloxazolopyridines.

Metastable mass-analyzed ion kinetic energy (MIKE) and collision-induced dissociation MIKE spectrometries have been applied to the study of all members of two classes of heteroaromatic isomers: 3-methylisoxazolo-and 2-methyloxazolopyridines. The study revealed that tandem mass spectrometry can characterize and differentiate the isomeric ion structures produced by these heterocycles. In particular, the MIKE spectra of both the molecular ions and abundant fragments formed by CO and CH3CN losses show characteristic differences that allow distinction among the isomers dependent on the position of the nitrogen atom in the pyridine ring, and distinction of isoxazole derivatives from oxazoles. The results indicate that the isomerization of the isoxazole moiety to oxazole-proposed for other analogous compounds-does not occur in these heterocyclic systems. The experimental work is supported by molecular orbital calculations both on neutral molecules and on molecular and fragment ions.

Steroid spectrum in human urine as revealed by gas chromatography V. Identification and quantitation of 3 alpha, 20 alpha-dihydroxy-5-beta pregnan-11-one (11-keto-pregnanediol) during different stages of development in children with C/21 hydroxylase deficiency.

A component was observed in the steroid spectrum of the urine of salt-loosing children with C/21-hydroxylase deficiency, which was eluted from Sp 2100 stationary phase before pregnanetriol but, unlike pregnanetriol, exhibited heat and acid stability. This component was isolated by paper chromatography and identified as 3 alpha, 20 alpha-dihydroxy-5 beta-pregnan-11-one by GC-MS and further gas chromatographic analysis. The amount of the steroid was minimal in the urine of infants, while in children submitted to substitution corticoid therapy it showed an increasing tendency, especially during puberty. The maximal value of excretion, in one case, amounted to 17% relative to total steroids. In puberty a significant excretion of 11-keto-pregnanediol indicates that under the given conditions the 11 beta-hydroxylation of steroid intermediates in the adrenals may be considerable not only at the level of 11-hydroxy-progesterone but also at that of progesterone.

Metabolism of vincamine in the rat in vivo and in vitro.

Metabolism of vincamine has been studied in rats in vivo and in vitro using tritium labelled vincamine. Radioactivity was excreted with urine and faeces in an amount of about 62% during 72 h after i.v., i.p. and p.o. administration of the drug. From bile about 40% radioactivity could be recovered during 6 h following i.p. administration. Vincamine is excreted in unchanged form in an amount of 4-6%. In an in vitro system containing rat liver homogenate 6 alpha- and 6 beta-hydroxy-vincamine are formed, as their structures could be deduced from the mass spectrometric data. Rat plasma probably hydrolizes vincamine to vincaminic acid, but the presence of vincaminic acid could not be demonstrated, neither in urine nor in bile. Mass spectrometric investigations of the urinary and biliary metabolites have shown that beyond 6 alpha- and 6 beta-hydroxy-vincamine, their further oxidized form, 6-keto-vincamine also appears. 6 alpha-, 6 beta-hydroxy-vincamine, 6-keto-vincamine and vincamine are eliminated with urine and bile in part as conjugates. Among the metabolites (+)-eburnamonine (vincamone) was also found, which is supposed to be the degradation product of vincaminic acid. The identified compounds are responsible for about 70% of urinary and 30% of biliary radioactivities.

Steroid spectrum in human urine as revealed by gas chromatography. III. Identification and quantitation of pregnenediol at different stages of bodily development.

Gas chromatographic analysis of steroids using Sp-2100 stationary phase revealed that all urine samples from 34 healthy children (aged 4-14 years) and from 35 adults contained 5-pregnene-3 beta, 20 alpha-diol, which was also identified by GC-MS. The extent of pregnenediol excretion continuously increased from prepuberty to adult age. The observed increase in pregnenediol excretion during prepuberty points to an enhanced biosynthetic activity of the adrenal gland in the years preceding sexual maturation.

Metabolism of mesocarb in the rat.

1. Rats treated orally with [14C]mesocarb (I; 3-(1-methyl-2-phenyl[2-(14C]ethyl)-N-(phenylaminocarbonyl)sydnone imine) (50 mg/kg) excrete 35% of the radioactivity in 24 h urine and 51% in 48 h urine. 2. Only traces of unchanged drug were found in urine. Hydroxy-mesocarb (II), dihydroxy-mesocarb (III), amphetamine (VII) and the conjugates of II and III account for 86% of the urinary radioactivity. 3. Cannulated male rats excrete about 40% of the radioactivity in 30 h in bile, mainly as conjugates of II and III.

Pharmacokinetics of vinpocetine in humans.

The pharmacokinetics of ethyl-apovincaminate (vinpocetine, Cavinton), a new vincamine derivative has been studied in volunteers after p.o. and i.v. administration. The concentration of the drug was determined by mass-fragmentography in human plasma. There was a biphasic elimination of the substance after i.v. injection with a T1/2 alpha of 0.136 h and with a T1/2 beta of 4.83 h. The value of Vdss (2.1 l/kg) shows a high adsorption of the drug by tissue proteins. The clearance rate of elimination was 0.366 l/h/kg. Oral administration of the drug resulted in maximum plasma concentration 1--1.5 h after the administration with values of 20--62 ng/ml. The bioavailability of the drug--calculated from the ratio of the areas under the concentration-time curves--proved to be 56.6 +/- 8.9%. Unchanged vinpocetine could not be detected in urine. From the results two-compartment open models were constructed and the steady state concentrations after multiple dosing were computed.