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PubMed2007

Biodegradation of bisphenol A and related compounds by Sphingomonas sp. strain BP-7 isolated from seawater.

A bacterium capable of assimilating 2,2-bis(4-hydroxyphenyl)propane (bisphenol A), strain BP-7, was isolated from offshore seawater samples on a medium containing bisphenol A as sole source of carbon and energy, and identified as Sphingomonas sp. strain BP-7. Other strains, Pseudomonas sp. strain BP-14, Pseudomonas sp. strain BP-15, and strain no. 24A, were also isolated from bisphenol A-enrichment culture of the seawater. These strains did not degrade bisphenol A, but accelerated the degradation of bisphenol A by Sphingomonas sp. strain BP-7. A mixed culture of Sphingomonas sp. strain BP-7 and Pseudomonas sp. strain BP-14 showed complete degradation of 100 ppm bisphenol A within 7 d in SSB-YE medium, while Sphingomonas sp. strain BP-7 alone took about 40 d for complete consumption of bisphenol A accompanied by accumulation of 4-hydroxyacetophenone. On a nutritional supplementary medium, Sphingomonas sp. strain BP-7 completely degraded bisphenol A and 4-hydroxyacetophenone within 20 h. The strain degraded a variety of bisphenols, such as 1,1-bis(4-hydroxyphenyl)ethane, 2,2-bis(4-hydroxy-3-methylphenyl)propane, 2,2-bis(4-hydroxyphenyl)butane, and 1,1-bis(4-hydroxyphenyl)cyclohexane, and hydroxy aromatic compounds such as 4-hydroxyacetophenone, 4-hydroxybenzoic acid, catechol, protocatechuic acid, and hydroquinone. The strain did not degrade bis(4-hydroxyphenyl)methane, bis(4-hydroxyphenyl)sulfone, or bis(4-hydroxyphenyl)sulfide.

Benzhydryl Compounds↗
PubMed2004

Antioxidative effects of glycosyl-ascorbic acids synthesized by maltogenic amylase to reduce lipid oxidation and volatiles production in cooked chicken meat.

Glycosylated ascorbic acids were synthesized by using the transglycosylation activity of Bacillus stearothermophilus maltogenic amylase with maltotriose to show effective antioxidative activity with enhanced oxidative stability. The modified ascorbic acids comprised mono- and di-glycosyl transfer products with an alpha-(1,6)-glycosidic linkage. The antioxidative effects of the glycosyl derivatives of ascorbic acid on the lipid oxidation of cooked chicken breast meat patties were compared, and the synergistic effect when combined with alpha-tocopherol was determined in terms of thiobarbituric acid-reactive substances (TBARS) and volatiles production during storage. The results indicate that the glycosylated ascorbic acids had very effective antioxidative activity in preventing lipid oxidation, and were better in their synergistic effect in comparison to authentic ascorbic acid, with maltosyl-ascorbic acid being the most effective. Volatiles production was highly correlated with the TBARS values in the lipid oxidation of cooked meat. The antioxidative effect preventing the production of volatiles was particularly strong on pentanal, fairly strong on propanal and butanal, and not at all on ethanal. Propanal, pentanal, and the total volatiles thus provided a good representation of the lipid oxidation status of cooked chicken meat.

Aldehydes↗
PubMed2003

Optimization of CH fluorescence diagnostics in flames: range of applicability and improvements with hydrogen addition.

This study quantifies the range of premixed flame conditions for which CH fluorescece diagnostics are applicable, and it shows that the CH fluorescence signal can be increased if some of the hydrocarbon fuel is replaced with hydrogen. The CH fluorescence signal is found to be adequate for fuel-air equivalence ratios (phi) as small as 0.85 for both methane-air and propane-air flames. The CH signal increases until a maximum at phi = 1.25 and phi = 1.35 for methane-air and propane-air flames, respectively, and then decreases for richer conditions. A strategy to increase the CH fluorescence signal and decrease interference from soot precursors is proposed by addition of the proper amount of hydrogen to the hydrocarbon fuel. Hydrogen addition reduces the background signal from soot precursors by as much as afactor of 10 and increases the CH fluorescence signal by as much as 80%. The normalized CH fluorescence measurements are compared with computations that utilize GRI-MECH 3.0 chemistry. Sources experimental uncertainties are discussed.

Journal Article↗
PubMedDate not supplied

Antibacterial and cytotoxic activity of prenylated bicyclic acylphloroglucinol derivatives from Hypericum amblycalyx.

Two new bicyclic acylphloroglucinol derivatives, hypercalyxone A (1-[5,7-dihydroxy-2-methyl-3-(3-methyl-but-2-enyl)-2-(4-methyl-pent-3-enyl)-chroman-8-yl]-2-methyl-propan-1-one, 1) and B (1-[5,7-dihydroxy-2-methyl-3-(3-methyl-but-2-enyl)-2-(4-methyl-pent-3-enyl)-chroman-8-yl]-2-methyl-butan-1-one, 2), have been isolated from the petroleum ether extract of the aerial parts of Hypericum amblycalyx, together with two further compounds (1-[5,7-dihydroxy-2-methyl-2-(4-methyl-pent-3-enyl)-chroman-8-yl]-2-methyl-propan-1-one, 3 and 1-[5,7-dihydroxy-2-methyl-2-(4-methyl-pent-3-enyl)-chroman-8-yl]-2-methyl-butan-1-one, 4), which have been described only as semi-synthetic products. In addition, the known triterpene lup-20(29)-en-3-one was obtained. Structure elucidation was based on 1D and 2D NMR studies, as well as on data derived from mass spectrometry. The four acylphloroglucinol derivatives were evaluated for their cytotoxic and antibacterial activity. All compounds showed moderate cytotoxic activity against KB and Jurkat T cancer cells. Especially compounds 3 and 4 exhibited a strong antibacterial activity against different Gram-positive strains.

Anti-Infective Agents↗
PubMed1999

Analysis of polymerization behavior of dental dimethacrylate monomers by differential scanning calorimetry.

The polymerization and copolymerization activity of dental monomers was investigated using the dynamic differential scanning calorimetry (DSC) method. As aliphatic dimethacrylate monomers, ethyleneglycol dimethacrylates with different lengths of ethyleneglycol and urethane dimethacrylates were used. As aromatic dimethacrylates, Bis-GMA (2,2-bis[4-(3-methacryloxy-2-hydroxypropoxy)phenyl]propane), BMPEPP (2,2-bis(4-methacryloxy poly-ethoxyphenyl)propane), and DMB (1,2-dimethacryloyloxy benzene) were used. Ethyleneglycol dimethacrylates showed sharp exothermic peaks, and the maximum temperatures (Tp) at the exothermic peaks of the DSC curves decreased according to the lengths of ethyleneglycols. Among urethane dimethacrylates, UDMA (dimethacryloxyethyl 2,2,4-trimethylhexamethylene diurethane) and DMPHU (di-(2-methacryloxypropyl) hexamethylene diurethane) showed sharp exothermic peaks, but DMEHU (di-(2-methacryloxyethyl) hexamethylene diurethane) showed an endothermic peak as well as exothermic peaks. This suggests that reactions other than polymerization occurred in the case of DMEHU. The polymerization activity of aromatic dimethacrylates was lower than that of ethyleneglycol dimethacrylates and urethane dimethacrylates. The copolymerization activity of TEGDMA (triethyleneglycol dimethacrylate) and DMB was also investigated using the dynamic DSC method. The DSC curves of the copolymerization between DMB and UDMA or BMPEPP showed broad peaks, but the DSC curves of the copolymerization between TEGDMA and UDMA or BMPEPP showed sharp peaks. The copolymerization activity of TEGDMA was better than that of DMB.

Bisphenol A-Glycidyl Methacrylate↗
PubMed1985

Dearylation and other cleavage reactions of diethylstilbestrol: novel oxidative pathways mediated by peroxidases.

Oxidation of diethylstilbestrol (I) by peroxidases from horseradish or mouse uterus in the presence of H2O2 in vitro leads to Z,Z-dienestrol (II) and to a number of cleavage products, five of which were identified by g.l.c.-mass spectrometry and comparison with authentic reference compounds as 4-hydroxybenzoic acid (III), 4'-hydroxypropiophenone (IV), 1'(4'-hydroxyphenyl)-propan-1-on-2-ol (V), 1-(4'-hydroxyphenyl)-propan-1,2-dione (VI) and 3-(4'-hydroxyphenyl)-hex-2-en-4-one (VII). The formation of 3-(4'-hydroxyphenyl)-hex-2-en-4-one (VII) from diethylstilbestrol is the first reported example of a metabolic dearylation reaction. The amount of cleavage products depends on the excess of H2O2 used. The amount of H2O2 does not affect the extent of binding of diethylstilbestrol to DNA as mediated by peroxidases. The syntheses of V, VI and VII are described.

Animals↗
PubMed1987

The metabolic disposition of [methoxy-14C]-labelled trans-anethole, estragole and p-propylanisole in human volunteers.

1. The metabolic fates of the naturally occurring food flavours trans-anethole and estragole, and their synthetic congener p-propylanisole, have been investigated in human volunteers using the [methoxy-14C]-labelled compounds. The doses used were close to those encountered in the diet, 1 mg, 100 micrograms and 100 micrograms respectively. 2. In each case, the major routes of elimination of 14C were in the urine and in the expired air as 14CO2. 3. Urinary metabolites were separated by solvent extraction, t.l.c. and h.p.l.c., and characterized by comparison of chromatographic mobilities with standards and by radioisotope dilution. Nine 14C urinary metabolites were found after trans-anethole administration, four after p-propylanisole and five after estragole. All were products of side chain oxidations. 4. The principal metabolites of p-propylanisole were 4-methoxyhippuric acid (12%) and 1-(4'-methoxyphenyl)propan-1-ol (2%) and -2-ol (8%). 5. The major metabolite of trans-anethole was 4-methoxyhippuric acid (56% of dose), accompanied by much smaller amounts of the two isomers of 1-(4'-methoxyphenyl)propane-1,2-diol (together 3%). 6. After estragole administration, the two volunteers eliminated 0.2 and 0.4% of the dose respectively as 1'-hydroxyestragole. 7. The human metabolic data is discussed with reference to the comparative metabolic disposition of these compounds in the mouse and rat, species commonly used in their safety assessment.

Adult↗
PubMed2000

Mechanism of formation of elastin crosslinks.

We examined the formation of quaternary pyridinium crosslinks of elastin formed by condensation of lysine and allysine residues using the model compounds propanal (allysine) and n-butylamine (lysine) under quasi-physiological conditions. The resulting pyridinium compounds were characterized and the structure compared with the known pyridinium crosslinks. Three pyridinium compounds were identified and the structures were identical with the skeleton of the crosslinking amino acids, desmosine (DES), isodesmosine (IDE), and pentasine. We concluded that a non-enzymatic pathway is available for the spontaneous generation of pyridinium crosslinks. To elucidate the intermediates and the mechanism of the formation of DES and IDE, we synthesized model intermediates from propanal and n-butylamine, and they were allowed to react in three kinds of solvents. Then, the products were analyzed by an ion-pair reverse-phase HPLC. The results of this model system indicated that DES and IDE can be formed by condensation of dehydromerodesmosine with dehydrolysinonorleucine and by condensation of allysine with dehydrolysinonorleucine, respectively. We also describe the mechanism of DES and IDE crosslinking.

2-Aminoadipic Acid↗
PubMed1998

Surfactant dissolution and water solubilization in chlorine-free liquified gas propellants.

The initial water content of a group of 15 pharmaceutically and toxicologically acceptable surfactants showed a tendency to increase with the surfactant hydrophilic-lipophilic balance (HLB) value. Surfactant solubility was determined in chlorine-free "alternative propellants" (n-butane, propane, dimethyl ether [DME], 1,1,1,2-tetrafluoroethane (HFA-134a), and 1,1,1,2,3,3,3-heptafluoropropane [HFA-227ea], and trichloromonofluoromethane [CFC-11] in the absence of cosolvents such as ethanol. Water-soluble surfactants such as Carbowax, Sentry, PEG 300, Tween 20, and Brij 30, with high HLB values showed appreciable solubility in HFA-134a and HFA-227ea. In systems containing > or = 80% propellant by weight, each single-phase propellant-surfactant blend was screened for its ability to solubilize iodine and dissolve or solubilize water with increasing surfactant concentration. This screening was performed to investigate the possibility of formulating high-volatility, single-phase systems with increased polarity and solvency from these conventional excipients and vehicles. Ternary-phase diagrams show the regions of apparent single and multiple phase behavior in each system. Despite the increased polarity of the hydrofluoroalkanes (HFAs), appreciable water solubility was seen only with these surfactants in DME and in the hydrocarbons (HCs) n-butane and propane.

Aerosol Propellants↗
PubMed1991

Free radical scavenging activity of carnosine.

The capacity of carnosine to decrease free radical-induced damage was evaluated using the oxidation of brain homogenates, the 2,2'-azobis-2-amidino propane-induced oxidation of erythrocyte ghost membranes, the radiation induced inactivation of horseradish peroxidase and the 2,2'-azobis-2-amidino propane-induced inactivation of lysozyme. Carnosine addition up to 17 mM did not produce any significant protection in either lipid peroxidation system, as assayed by the oxygen uptake rate. Carnosine addition reduces the intensity of the visible luminescence emitted, apparently due to a dark decomposition of the luminescent intermediates. Carnosine addition protects horseradish peroxidase and lysozyme from free radical mediated inactivation. The mean carnosine concentrations required to inhibit the inactivation rates by 50% were 0.13 mM and 0.6 mM for horseradish peroxidase and lysozyme, respectively.

Amidines↗
PubMed2006

Enhanced nutty flavor formation in cheddar cheese made with a malty Lactococcus lactis adjunct culture.

Nutty flavor in Cheddar cheese is desirable, and recent research demonstrated that 2- and 3-methyl butanal and 2-methyl propanal were primary sources of nutty flavors in Cheddar. Because malty strains of Lac-tococcus lactis (formerly Streptococcus lactis var. malti-genes) are characterized by the efficient production of these and other Strecker aldehydes during growth, this study investigated the influence of a malty L. lactis adjunct culture on nutty flavor development in Cheddar cheese. Cheeses made with different adjunct levels (0, 10(4) cfu/mL, and 10(5) cfu/mL) were ripened at 5 or 13 degrees C and analyzed after 1 wk, 4 mo, and 8 mo by a combination of instrumental and sensory methods to characterize nutty flavor development. Cheeses ripened at 13 degrees C developed aged flavors (brothy, sulfur, and nutty flavors) more rapidly than cheeses held at 5 degrees C. Additionally, cheeses made with the adjunct culture showed more rapid and more intense nutty flavor development than control cheeses. Cheeses that had higher intensities of nutty flavors also had a higher concentration of 2/3-methyl butanal and 2-methyl propanal compared with control cheeses, which again confirmed that these compounds are a source of nutty flavor in Cheddar cheese. Results from this study provide a simple methodology for cheese manufacturers to obtain consistent nutty flavor in Cheddar cheese.

Aldehydes↗
PubMed1988

Note on ethene and other low-molecular weight hydrocarbons in environmental tobacco smoke.

Levels of ethene and propene, together with those of some other light hydrocarbons (propane, butane, isobutane and ethyne), have been measured under realistic conditions in environmental tobacco smoke (ETS) as a step towards the elucidation of the sources of 2-hydroxyethyl and 2-hydroxypropyl adducts of hemoglobin observed in non-smokers. These adducts may reflect in vivo doses of carcinogenic epoxides that are metabolites of the respective alkenes. The data show that 2.0 mg ethene, 1.4 mg propene, and 0.7 mg propane together with smaller amounts of butane, isobutane and ethyne are released per cigarette smoked (0.66 g tobacco) of a common Swedish brand. The alkenes in ETS should be considered as contributing factors to a risk of systemic cancer from passive smoking. With regard to alkene intake, even a relatively mild exposure to ETS (2 cigarettes per h for 5 h per day in a 33 m3 room with one air change per hour is estimated to correspond to the active smoking of about one cigarette per day.

Alkenes↗
PubMed2005

New quaternary pyridine aldoximes as casual antidotes against nerve agents intoxications.

In this work, the ability of four newly synthesized oximes--K005 (1,3-bis(2-hydroxyiminomethylpyridinium) propane dibromide), K027 (1-(4-hydroxyiminomethylpyridinium)-3-(4-carbamoylpyridinium) propane dibromide), K033 (1,4-bis(2-hydroxyiminomethylpyridinium) butane dibromide) and K048 (1-(4-hydroxyiminomethylpyridinium)-4-(4-carbamoylpyridinium) butane dibromide) to reactivate acetylcholinesterase (AChE, EC 3.1.1.7) inhibited by nerve agents is summarized. Reactivation potency of these compounds was tested using standard in vitro reactivation test. Tabun, sarin, cyclosarin and VX agent were used as appropriate testing nerve agents. Rat brain AChE was used as a source of the enzyme. Efficacies of new reactivators to reactivate tabun-, sarin-, cyclosarin- and VX-inhibited AChE were compared with the currently used AChE reactivators (pralidoxime, obidoxime and HI-6). Oxime K048 seems to be promising reactivator of tabun-inhibited AChE. Its reactivation potency is significantly higher than that of HI-6 and pralidoxime and comparable with the potency of obidoxime. The best reactivator of sarin-inhibited AChE seems to be oxime HI-6. None of the new AChE reactivators reached comparable reactivation potency. The same results were obtained for cyclosarin-inhibited AChE. However, oxime K033 is also potent reactivator of AChE inhibited by this nerve agent. In the case of VX inhibition, obidoxime and new oximes K027 and K048 seem to be the best AChE reactivators. None from the currently tested AChE reactivators is able to reactivate AChE inhibited by all nerve agents used and, therefore, the search for new potential broad spectrum AChE reactivators is needed.

Acetylcholinesterase↗
PubMed1999

Tumor radiosensitization by sustained intratumoral release of bromodeoxyuridine.

We have previously reported that the use of the polymer bis(p-carboxyphenoxy)propane-sebacic acid (20:80) for intratumoral delivery of cis-platinum in a mouse tumor model (RIF-1) potentiated the effects of acute and fractionated radiation. This mode of drug delivery seems particularly applicable to the administration of radiosensitizing drugs because an optimum concentration of radiosensitizer can be maintained in the tumor over the prolonged period required for fractionated radiation treatment. We have now investigated, in the same tumor model, radiosensitization by the thymidine analogue bromodeoxyuridine (BrdUrd). BrdUrd (20%, w/w) was incorporated into bis(p-carboxyphenoxy)propane-sebacic acid (20:80) and polymer rods containing the drug implanted in the RIF-1 tumor. Preliminary in vitro studies of the rate of release of BrdUrd from the polymer showed an initial rapid loss over 24 h, followed by a slower release extending over the next 5 days. In experiments in which tumor cells, which had incorporated BrdUrd in vivo from implanted polymer, were excised and a single cell suspension irradiated in vitro radiosensitization indicative of BrdUrd incorporation was associated mainly with an increase in the alpha constant for the linear quadratic model of cell survival. Radiosensitization was seen for tumor cells harvested between 5 and 10 days after polymer implant, a finding that is consistent with results of experiments in which the percentage of cells that had incorporated BrdUrd were measured by flow cytometry at various times after polymer/BrdUrd implant. The proportion of tumor cells positive for BrdUrd was 40-50% between 3 and 8 days after polymer implant. When tumors were irradiated in situ and response measured in terms of tumor growth delay (TGD), radiosensitization was not seen for an acute dose of 16.5 Gy. In contrast, significant radiosensitization was seen for fractionated treatments when polymer/BrdUrd was implanted 3 days before the first radiation dose. For a dose of 5 x 6 Gy, TGD was increased from 22 days for radiation alone to 27 days for radiation plus polymer implant. For 10 x 6 Gy fractions, TGD increased from 45-77 days for those mice in whom the tumor eventually regrew, whereas for 25% of the mice in this group the tumor volume was reduced to a point where it was no longer detectable and there was no recurrence for at least 120 days after treatment.

Animals↗
PubMedDate not supplied

Correlation of chemopreventive efficacy data from the human epidermal cell assay with in vivo data.

Continuous exposure to low doses of potentially mutagenic and carcinogenic chemicals over the human lifetime makes the identification of agents, which could reduce the ensuing risk of cancer, beneficial. The Human Epidermal Cell (HEC) Assay includes multiple exposures to low, non-toxic doses of propane sultone, which increases cellular growth and inhibits differentiation, and co-exposure to potential chemopreventive agents to determine their ability to inhibit the increased growth or increase differentiation. Original data are presented on the efficacy of twenty potential cancer chemopreventive agents were screened for efficacy in the HEC Assay. Efficacy was determined by the ability of agents, at nontoxic concentrations, to reverse either of the propane sultone-induced biomarkers, enhanced growth and reduced involucrin expression. Based on the number of positive concentrations and the lack of toxicity, 1,2-dithiol-3-thione, oltipraz, and a synthetic retinoid, Ro 16-9100, were the most active. Eleven of seventeen positive agents were active for both endpoints. S-Allylcysteine was only active for the growth inhibition endpoint, and DFMO, Iycopene, perillyl alcohol, ursodiol, and black tea polyphenols were only active for the involucrin endpoint. The three agents that have been shown to be negative in animal models, diphenhydramine, d-mannitol, and nordihydroguaiaretic acid, were correctly identified as negative by the assay. When the data from previous studies (Elmore et al, Anticancer Res, 19: 909-918, 1999) are included, a positive response in one or more endpoints of the HEC Assay correlates 100% (26/26) with a positive response in one or more of the animal cancer prevention models (8). The available data suggest that the HEC Assay response is highly predictive of efficacy in animals in vivo with an overall accuracy of 90%. Future studies will include data with additional negative agents. The correlation of the HEC Assay data with data from in vivo studies in animal models, which utilize multiple carcinogens and multiple target organs, would suggest that this in vitro assay has the ability to identify agents with the potential to prevent carcinogen-induced cancer. While our ultimate goal is to identify agents with potential efficacy for preventing human cancer, sufficient human data are not yet available to make this correlation.

Anticarcinogenic Agents↗
PubMed2001

Biochemical characterization and mechanism of action of a thermostable beta-glucosidase purified from Thermoascus aurantiacus.

An extracellular beta-glucosidase from Thermoascus aurantiacus was purified to homogeneity by DEAE-Sepharose, Ultrogel AcA 44 and Mono-P column chromatography. The enzyme was a homotrimer, with a monomer molecular mass of 120 kDa; only the trimer was optimally active at 80 degrees C and at pH 4.5. At 90 degrees C, the enzyme showed 70% of its optimal activity. It was stable at pH 5.2 and at temperatures up to 70 degrees C for 48 h, but stability decreased above 70 degrees C and at pH values above and below 5.0. The enzyme hydrolysed aryl and alkyl beta-d-glucosides and cello-oligosaccharides, and was specific for substrates with a beta-glycosidic linkage. The hydroxy groups at positions 2, 4 and 6 of a glucose residue at the non-reducing end of a disaccharide appeared to be essential for catalysis. The enzyme had the lowest K(m) towards p-nitrophenyl beta-d-glucoside (0.1137 mM) and the highest k(cat) towards cellobiose and beta,beta-trehalose (17052 min(-1)). It released one glucose unit at a time from the non-reducing end of cello-oligosaccharides, and the rate of hydrolysis decreased with an increase in chain length. Glucose and d-delta-gluconolactone inhibited the beta-glucosidase competitively, with K(i) values of 0.29 mM and 8.3 nM respectively, while methanol, ethanol and propan-2-ol activated the enzyme. The enzyme catalysed the synthesis of methyl, ethyl and propyl beta-d-glucosides in the presence of methanol, ethanol and propan-2-ol respectively with either glucose or cellobiose, although cellobiose was preferred. An acidic pH favoured hydrolysis and transglycosylation, but high concentrations of alcohols favoured the latter reaction. The stereochemistry of cellobiose hydrolysis revealed that beta-glucosidase from T. aurantiacus is a retaining glycosidase, while N-terminal amino acid sequence alignment indicated that it is a member of glycoside hydrolase family 3.

Alcohols↗
PubMed2001

Comparison of the modulatory effects of human and rat liver microsomal metabolism on the estrogenicity of bisphenol A: implications for extrapolation to humans.

Bisphenol A [BPA, 2,2-bis(4-hydroxyphenyl)propane], a xenoestrogen, is a monomer for the synthesis of polycarbonate plastics, epoxy resins, and composites. Metabolism of BPA to the monoglucuronide will determine the extent of its estrogenicity in vivo. Investigation of the metabolism of BPA (500 microM) by isolated female rat hepatocytes confirmed the formation of BPA glucuronide as the major metabolite. There was a significant difference (p < 0.05) between the V(max) (mean +/- S.E.M., n = 4) of glucuronidation by pooled male or female human (four livers in each case) and immature female rat liver microsomes (5.9 +/- 0.4, 5.2 +/- 0.3, and 31.6 +/- 8.1 nmol/min/mg of protein, respectively). Estrogenic activity of BPA, assessed in a coupled microsomal metabolism-yeast estrogenicity assay, was decreased 3- and 7-fold following glucuronidation by human female and immature female rat liver microsomes, respectively. Incubations of BPA with pooled human or rat liver microsomes, in the presence of NADPH, resulted in the formation of 5-hydroxybisphenol A [2-(4,5-dihydroxyphenyl)-2-(4-hydroxyphenyl)propane], which was 10-fold less potent than BPA in the yeast estrogenicity assay. However, there was insufficient turnover to achieve a significant effect on the estrogenic activity of BPA. Because human liver microsomes did not glucuronidate BPA as extensively as the rat liver microsomes, estrogen target tissues in humans may be subject to greater exposure to BPA than the tissues of the immature female rats used for assessing estrogenicity of xenobiotics.

Adult↗
PubMed1992

Study of activated oxygen production by some thiols using chemiluminescence.

2-3-dimercapto-1-propane sulfonic acid, D-penicillamine and meso-dimercapto succinic acid, drugs widely applied as antidota against metal poisoning, and cysteine and glutathione were studied with respect to their ability to generate and to scavenge superoxide anion radical. Superoxide production and scavenging were tested by means of luminol-dependent chemiluminescence. In presence of 1 mumol/l ADP-Fe3+ only cysteine and meso-dimercapto succinic acid induced chemiluminescence which could be inhibited by superoxide dismutase. 2,3-dimercapto-1-propane sulfonic acid, D-penicillamine and glutathione acted as O2- scavengers. These thiols inhibited O2(-)-dependent lipid peroxidation thus acting as antioxidants, whereas cysteine and meso-dimercapto succinic acid accelerated peroxidation. It is suggested that the toxic side effects of thiols may be due to their ability to generate or to scavenge free radicals.

Cysteine↗