Multiplug filtration cleanup method with multi-walled carbon nanotubes for the analysis of malachite green, diethylstilbestrol residues, and their metabolites in aquatic products by liquid chromatography-tandem mass spectrometry.

The food safety supervision in aquatic products has raised public concern in recent years. In this study, a liquid chromatographic-tandem mass spectrometric (LC-MS/MS) method for the simultaneous quantification and identification of four residues of the ever widely used analytes (including malachite green, leucomalachite green, diethylstilbestrol, and dienestrol) in aquaculture samples was developed. For sample preparation, a modified QuEChERS (quick, easy, cheap, effective, rugged, and safe) method was used, which was initially developed for pesticide residue analysis. For cleanup procedure, low-temperature cleanup method was combined with multiplug filtration cleanup (m-PFC) method based on multi-walled carbon nanotubes (MWCNTs). The volume of water, extraction solvent, cleanup sorbents, and m-PFC procedure were optimized for carp, striped bass, and giant salamander matrices. It was validated by analyzing four residues in each matrix spiked at three concentration levels of 0.5, 5, and 50 µg/kg (n = 5). The method was successfully validated according to the 2002/657/EC guidelines. After optimization, spike recoveries were within 73-106 % and <15 % relative standard deviations (RSDs) for all analytes in the tested matrices. Limits of quantification (LOQs) for the proposed method ranged from 0.10 to 0.50 µg/kg. Matrix-matched calibrations were performed with the coefficients of determination >0.998 between concentration levels of 0.5 and 200 µg/kg. The developed method was successfully applied to the determination of residues in market samples. Graphical abstract Flow chart of multi-plug filtration cleanup combined with low-temperature cleanup method.

Involvement of prostaglandin synthetase in the peroxidative metabolism of diethylstilbestrol in Syrian hamster embryo fibroblast cell cultures.

The mechanism for induction of tumors by estrogens is still unresolved. Neoplastic transformation of Syrian hamster embryo fibroblasts by diethylstilbestrol (DES) suggests that established principles of chemical carcinogenesis may be involved. The Syrian hamster embryo fibroblast cells provide a system in which now the question can be asked whether the metabolic activation of DES is a prerequisite for its biological activity in this system. In this study, Syrian hamster embryo fibroblast cell cultures were shown to oxidatively metabolize DES to cis,cisdienestrol (Z,Z-DIES) which is a DES metabolite commonly found in vivo. The only other metabolic conversion of DES detectable in these cell cultures was the formation of the glucuronides of DES and Z,Z-DIES. Z,Z-DIES is formed more efficiently in incubations with rapidly growing cells than in cultures approaching confluence. When arachidonic acid was added to the medium, Z,Z-DIES formation was enhanced, whereas indomethacin added to the cell cultures inhibited the formation of this metabolite. These data suggest the involvement of prostaglandin synthetase in the oxidative metabolism of DES by Syrian hamster embryo fibroblast cells in culture and suggest that cooxidation may play a role for its biotransformation in whole cells. Moreover, since many competing metabolic pathways are available to DES in vivo, this present study adds important additional support to the hypothesis that metabolism of DES via a peroxidative route plays a role in its carcinogenicity.

Chemiexcitation in the peroxidative metabolism of diethylstilbestrol. Metabolic products.

In the presence of the surfactant hexadecyltrimethyl ammonium bromide (CTAB) a cascade of electronically excited states accompanies the successive steps in the peroxidative metabolization of the strong estrogenic and tumourogenic diethylstilbestrol. Reversing the order by necessity, we report in this first paper results with the metabolites. Exposure of 4-hydroxypropiophenone, Z,Z-dienestrol or E,E-dienestrol to horseradish peroxidase and H2O2 promotes oxygen uptake and spectral alterations. Light emission is observed provided that the surfactant CTAB is present. With the three substrates, 4-hydroxybenzoic acid and a new metabolite, p-benzoquinone, have been identified. With both dienestrol isomers, 1-(4'-hydroxyphenyl)-propan-1-on-2-ol has been identified. In all cases the emission spectrum indicates the presence of several emitters. Possible chemiexcitation routes are pointed out. From the dramatic increase of the emission by enhancers, values as high as 1 x 10(-5) are inferred for the product of the quantum yields of chemiexcitation and energy transfer.

Non-estrogenic metabolites of diethylstilbestrol produced by prostaglandin synthase mediated metabolism.

Incubation of trans-diethylstilbestrol (E-DES) with prostaglandin synthase (PGS) in vitro leads to the formation of the metabolites cis, cis-dienestrol (Z,Z-DIES) and cis-diethylstilbestrol (Z-DES) which have considerably decreased estrogenic activity compared to their parent compound. Incubations of (14C)-E-DES with PGS in the presence of arachidonic acid (AA) predominantly catalyze formation of the oxidative metabolite Z,Z-DIES, accompanied by the formation of protein bound radioactivity. Inhibition of peroxidative metabolism through addition of indomethacin or absence of AA favors isomerization of E-DES to Z-DES without concomitant formation of protein bound radioactivity. Isomerization is inhibited by phenidone (1-phenyl-3-pyrazolidone). Since PGS activity is present in uterine tissue, these pathways may play a role in the metabolism of DES in its target tissue.

Performance of Leghorn type hens fed two levels of energy and a synthetic estrogen during the growing period.

Feeding of an estrogen, dienestrol diacetate, at 352 mg/kg of diet to December-hatched White Leghorn type pullets, from 16 to 20 wk of age, caused onset of production to be delayed approximately 3 wk. The dietary dienestrol diacetate also resulted in increased body weights at 30 and 46 wk in one experiment. Hens receiving the estrogen laid significantly (P less than .05) heavier but fewer eggs during most of the production year than did those fed diets without the estrogenic compound. The addition of 2.2% fat to diets of pullets from 0 to 20 wk of age failed to influence their performance in the layer house.

Characterization of semiquinone free radicals formed from stilbene catechol estrogens. An ESR spin stabilization and spin trapping study.

Electron spin resonance spectroscopy has been used to detect, characterize, and to infer structures of o-semiquinones derived from stilbene catechol estrogens. Radicals were generated enzymatically using tyrosinase and were detected as their Mg2+ complexes. It is suggested that initial hydroxylation of stilbene estrogen gives a catechol estrogen in situ; subsequent two-electron oxidation of the catechol to the quinone, followed by reverse disproportionation, leads to the formation of radicals. Consistent with this mechanism, o-phenylenediamine, a quinone trapping agent, inhibits formation of o-semiquinones. A competing mechanism of radical production involves autoxidation of the catechol. Hydroxyl radicals are shown to be produced in this system via a mechanism involving reduction of iron and copper complexes by stilbene catechols. Possible differences in the reactivity of stilbene ortho- and para-semiquinones are discussed.

Diethylstilbestrol: evidence for metabolic activation in man, rat, and hamster.

Oxidative biotransformation of radioactively and deuterium-labeled DES gives rise to several metabolites in intact Wistar rats, Syrian golden hamsters, and humans. With the use of radio gas chromatography and gas chromatography--mass spectrometry, the major urinary and biliary metabolites were tentatively identified as hydroxy and methoxy derivatives of DES and dienestrol, of which the relative amounts excreted depended largely on the species. Some of the metabolites are potentially reactive substances or have reactive metabolic precursors such as epoxides or allylic hydroxy compounds that might be associated with the adverse effects of DES.

Metabolism of diethylstilbestrol: identification of a catechol derived from dienestrol.

The enzymatic oxidation of E-3,4-bis-(p-hydroxyphenyl)-hex-3-ene (diethylstilbestrol) by either mushroom tyrosinase or rat liver microsomes in the presence of NADPH and air yields a catechol. Upon further oxidation of both compounds with periodate and condensation of the resulting o-quinones with o-phenylenediamine, phenazines are produced. The phenazines derived from the products of both the plant and animal enzyme systems are identical to the product obtained by oxidation of diethylstilbestrol with potassium nitrosodisulfonate and condensation of the o-quinone produced with o-phenylenediamine. High and low resolution mass spectra of the phenazine are consistent with its derivation from a catechol having two fewer hydrogens than diethylstilbestrol.

The mass spectra of diethylstilbestrol and related compounds.

The low resolution mass spectra of E-3,4-bis-(p-hydroxyphenyl)-hex-3-ene (diethylstilbestrol), E-[1,1,1-3H3]3,4-bis-(p-hydroxyphenyl)-hex-3-ene, E-2,3-bis-(p-hydroxyphenyl)-but-2-ene (dimethylstilbestrol), E,E-3,4-bis-(p-hydroxyphenyl)hexa-2,4-diene (dienestrol) and 3,4-bis-(p-hydroxyphenyl)-hexane (hexestrol) were examined as the parent compounds, their diacetates, dimethyl ethers, and bis-trimethylsilyl ethers. In addition, the mass spectra of the diethyl ether and the hexadeuteriodimethyl ether of E-3,4-bis-(p-hydroxyphenyl)-hex-3-ene were studied. Each compound gives rise to several sets of characteristic fragment ions associated with loss of alkyl groups, loss of aryl groups and rearrangements. An ion of m/e 165 (C13H9) was found in the spectra of all the compounds studied. With the aid of high resolution mass spectrometry empirical formulae were assigned to major ions of the free diphenols.

The metabolism of diethylstilbestrol.

PIP: This literature review presents available data on the metabolism of diethylstilbestrol (DES) to shed light on the fate and the mechanism of toxicity of this compound. Biotransformation effects reviewed include conjugation reactions of DES such as glucuronide formation in vivo and in vitro, enterohepatic circulation of DES and its glucuronide, and formation of steroid sulfatases and sulfates; oxidative metabolism of DES (aromatic hydroxylation followed by methylation); and species differences in DES metabolism. Excretion curves for 12 animal species show vast differences; whereas urinary excretion predominates in humans, chimps, rhesus monkeys, and guinea pigs; rats, hamsters, and mice show predominately fecal elimination. The difference among species seems due to capability of biliary excretion. A molecular weight threshold seems to exist, and this may account for the varying remnants of DES housed in different species' organs. Placental transfer is another major problem. Fetuses of many species seem capable of glucurondizing DES. The formation of reactive metabolites (i.e., affinity for estradiol 17-beta receptor attachment and affinity for other proteins bound by estrogen) through oxidative biotransformation suggests that DES metabolites affect hepatic systems and may activate or transform cells to malignancy. Theories of the organotropism of DES carcinogenicity are presented, as well as a discussion of the fate of DES in the environment.^ieng

The role of the estrogen receptor in diethylstilbestrol toxicity.

The site and specificity of the tissue response to a toxicant are of central importance; it is in this area of diethylstilbestrol (DES) toxicity that the estrogen receptor would appear to play its primary role. Compilation of the various sites of DES toxicity in humans and experimental animals indicates that lesions appear predominantly in estrogen responsive target tissues suggesting that the presence of the estrogen receptor in such target tissues may help govern the tissue specificity of the toxic insult. DES and many of its oxidative metabolites interact with high affinity with the estrogen receptor. Such an interaction may be responsible for localizing DES to target tissues. Autoradiographic and biochemical studies have supported the localization of radiolabeled DES in susceptible tissues. The intracellular mechanism of receptor binding of DES and certain metabolites could then result in mobilization of these compounds to the nucleus. Experimental evidence has shown that DES and a number of its metabolites are able to translocate receptor to the nucleus of uterine cells. Such an action by the receptor results in an increased probability of potential chemical interactions with the genome. The actual induction of a chemical lesion in the target cell may, at this point, proceed by non-receptor mediated mechanisms. For example, studies using in vitro cell culture systems which contain no estrogen receptors have shown that DES can induce neoplastic cell transformation, mutagenesis, irreversible binding to DNA and protein and unscheduled DNA synthesis. These results raise the possibility that a part of DES toxicity may follow pharmacologic principles established for chemical carcinogens. Following induction of the molecular lesion, the role of the receptor continues in this process by mediating increased protein synthesis and mitogenesis in responsive target tissues which ultimately permits a more extensive expression of the toxic effects. It has been demonstrated that DES is a potent mitogen in vivo in both uterine and pituitary tissues, subsequently, the lesion will perpetuate itself through this receptor mediated biological response. This is particularly important since a number of DES induced reproductive tract tumors are expressed only after additional estrogen exposure. While other tumors have been shown to be estrogen sensitive and will regress without continued estrogen stimulation. Therefore, it should be considered that the presence of the estrogen receptor and the estrogen receptor mediated biological responsiveness of a particular tissue are most important in explaining the specificity of DES toxicity.