Identification of hydroxylated metabolites in 2,2',4,4'-tetrabromodiphenyl ether exposed rats

Faeces from day 1-5 of orally administered 2,2',4,4'-tetrabromodiphenyl ether (BDE-47) in rat have been analysed for hydroxylated metabolites. Six hydroxylated tetrabrominated diphenyl ethers, as well as three hydroxylated tribrominated diphenyl ethers found, were structurally identified. They were 2'-hydroxy-2,4,4'-tribromodiphenyl ether, 3'-hydroxy-2,4,4'-tribromodiphenyl ether, 4'-hydroxy-2,2',4-tribromodiphenyl ether, 6-hydroxy-2,2',4,4'-tetrabromodiphenyl ether, 2'-hydroxy-2,3',4,4'-tetrabromodiphenyl ether, 3-hydroxy-2,2',4,4'-tetrabromodiphenyl ether, 5-hydroxy-2,2',4,4'-tetrabromodiphenyl ether, 4'-hydroxy-2,2',4,5'-tetrabromodiphenyl ether and 4-hydroxy-2,2',3,4'-tetrabromodiphenyl ether. The analysis was performed using gas chromatography-mass spectrometry (GC-MS). The identification of the hydroxylated polybrominated diphenyl ether (OH-PBDE) metabolites in the rat faeces was supported by similar relative retention times (RRTs) versus 2,2',3,4,4',5-hexabromodiphenyl ether (BDE-138) on two columns of different polarities compared to the authentic references. The identification of the OH-PBDE metabolites was also supported by full scan electron ionisation mass spectra. Two of the identified OH-PBDE metabolites have identical structures as natural products, which previously have been isolated from marine sponges and an ascidian.     

Light-induced transformation of tribenuron-methyl on glass, soil, and plant surface

Photolysis of tribenuron-methyl (methyl 2-[[[[N-(4-methoxy-6-methyl-1,3,5triazin-2-yl)methylamino]carbonyl]amino]sulfonyl]benzoate), a sulfonylurea herbicide, was studied as thin film on glass surface, soil surface, and plant surface. A number of photoproducts such as 4-methoxy-6-methyl-2-aminomethyl-1,3,5-triazine; methyl-2-(aminosulfonyl) benzoate; N-(2-carbomethoxyphenyl)-N-(4-methoxy-6-methyl-1,3,5-triazin-2-yl)-N'-methylurea; N-(2-carbomethoxyphenyl sulfonyl)-N-methyl urea; o-benzoic sulfimide and 4-methoxy-6-methyl-2-amino-1,3,5-triazine were identified by comparison of their GC-MS with the authentic standards. The rate of degradation in all the cases followed first-order kinetics with a statistically significant correlation coefficient. Rate of photodegradation was greater on glass surface than on soil surface.     

Degradation of juvenile hormone analog by soil microbial isolates

Juvenoids are efficient pesticides with relatively low toxicity to humans. However, few studies have evaluated the effect of degradation by soil microorganisms on their toxicity. The effects of bacterial, fungal and yeast isolates on aerobic decomposition of ethyl N-[2-[4-(2,2-ethylenedioxy-1-cyclohexylmethyl)phenoxy]ethyl] carbamate during eight weeks were determined. The effect of different concentration of glucose on their degradation activity is also analyzed.     

Leaching and degradation of ethametsulfuron-methyl in soil

Leaching and degradation of the herbicide ethametsulfuron-methyl[methyl 2-[(4-ethoxy-6-methylamino-1,3,5-triazine-2-yl)carbamoylsulfamoyl]benzoate] in three soils were investigated under laboratory conditions. Ethametsulfuron-methyl was mobile on soils when tested using non-aged and aged soil columns; this mobility agreed reasonably well with Freundlich soil isotherm constants. It was found that ethametsulfuron-methyl was more mobile in alkaline sandy Vertisol soil and neutral loamy Alfisol soil than in acidic clayey Red soil. Degradation of ethametsulfuron-methyl in soils was pH-dependent; calculated half-life (t(1/2)) values ranged from 13 to 67 days. Ethametsulfuron-methyl was more persistent in neutral or weakly basic than in acidic soil. Five soil metabolites were isolated and identified by LC/MS/MS analysis. The degradation pathways included the cleavage of the sulfonylurea bridge, N- and O-dealkylation, and triazine ring opening.     

Metabolism of the nonylphenol isomer [ring-U-14C]-4-(3',5'-dimethyl-3'-heptyl)-phenol by cell suspension cultures of Agrostemma githago and soybean

The biotransformation of the nonylphenol isomer [ring-U-14C]-4-(3',5'-dimethyl-3'-heptyl)-phenol (4-353-NP, consisting of two diastereomers) was studied in soybean and Agrostemma githago cell suspension cultures. With the A. githago cells, a batch two-liquid-phase system (medium/n-hexadecane 200:1, v/v) was used, in order to produce higher concentrations and amounts of 4-353-NP metabolites for their identification; 4-353-NP was applied via the n-hexadecane phase. Initial concentrations of [14C]-4-353-NP were 1 mg L(-1) (soybean), and 5 and 10 mg L(-1) (A. githago). After 2 (soybean) and 7 days (A. githago) of incubation, the applied 4-353-NP was transformed almost completely by both plant species to four types of products: glycosides of parent 4-353-NP, glycosides of primary 4-353-NP metabolites, nonextractable residues and unknown, possibly polymeric materials detected in the media. The latter two products emerged especially in soybean cultures. Portions of primary metabolites amounted to 19-22% (soybean) and 21-42% of applied 14C (A. githago). After liberation from their glycosides, the primary 4-353-NP metabolites formed by A. githago were isolated by HPLC and examined by GC-EIMS as trimethylsilyl derivatives. In the chromatograms, eight peaks were detected which due to their mass spectra, could be traced back to 4-353-NP. Seven of the compounds were side-chain monohydroxylated 4-353-NP metabolites, while the remaining was a (side-chain) carboxylic acid derivative. Unequivocal identification of the sites of hydroxylation/oxidation of all transformation products was not possible. The main primary metabolites produced by A. githago were supposed to be four diastereomers of 6'-hydroxy-4-353-NP (about 80% of all products identified). It was concluded that plants contribute to the environmental degradation of the xenoestrogen nonylphenol; the toxicological properties of side-chain hydroxylated nonylphenols remain to be examined.     

Studies on the origin of the methylsulfonyl-containing metabolites from propachlor.

Metabolites in which the chlorine from propachlor has been replaced by a cysteine group or a methylsulfonyl group [-S(O2) CH3] are present in the urine of rats dosed orally with propachlor. In the present study, urine from rats given single oral doses of 35S-labeled cysteine conjugate of propachlor contained metabolites having the methylsulfonyl groups labeled with 35S. No metabolites containing 14C-labeled methylsulfonyl groups were isolated from urine of rats given single oral doses of the cysteine conjugate of propachlor in which the cysteine group was uniformly labeled with 14C. These findings show that the cysteine conjugate of propachlor is the source of sulfur in the methylsulfonyl-containing metabolites. Therefore, we suggest that a C-S lyase present in the animal cleaves the cysteine conjugate of propachlor and thus allows further metabolism of the sulfur to a methylsulfonyl moiety.     

Light induced transformation of tribenuron-methyl

To study the photostability of sulfonylurea herbicide tribenuron-methyl (methyl 2-[[[[ N-(4-methoxy-6-methyl-1,3,5-triazin-2-yl) methylamino] carbonyl]amino]sulfonyl]benzoate), in the field, model experiments with organic solvents were performed. Irradiation of tribenuron-methyl in methanol, isopropanol and cyclohexane yielded 4-methoxy-6-methyl-2-aminomethyl-1,3,5-triazine; methyl-2-(aminosulfonyl) benzoate; N-(4-methoxy-6-methyl-1,3,5-triazin-2-yl)-N-methyl urea; N-(2-carbomethoxy phenyl)-N-(4-methoxy-6-methyl-1,3,5-triazin-2-yl)-N'-methyl urea; 2-(aminosulfonyl) benzoic acid, N-methyl saccharin and saccharin in considerable amounts. The rate of degradation in different solvents followed first-order kinetics with a statistically significant correlation coefficient.     

Effect of systemic herbicides on N2-fixing and phosphate solubilizing microorganisms in relation to availability of nitrogen and phosphorus in paddy soils of West Bengal

A field experiment has been conducted with four systemic herbicides viz., butachlor [N-(butoxymethyl)-2-chloro-2',6'-diethyl-acetanilide], fluchloralin [N-(2-chloroethyl)-(2,6-dinitro-N-propyl-4-trifluoromethyl) aniline], oxadiazon [5-terbutyl-3-(2,4-dichloro-5-isopro poxyphenyl)-1,3,4-oxadiazol-2-one] and oxyfluorfen [2-chloro-1-(3-ethoxy-4-nitrophenyl)-4-(trifluoromethyl) benzene] at their recommended field rates (2.0, 1.5, 0.4 and 0.12kga.i.ha(-1), respectively) to investigate their effects on growth and activities of aerobic non-symbiotic N(2)-fixing bacteria and phosphate solubilizing microorganisms in relation to availability of nitrogen and phosphorus in the rhizosphere soils as well as yield of the rice crop (Oryza sativa L cv. IR-36). Application of herbicides, in general, highly stimulated the population and activities of the target microorganisms, which resulted in a greater amount of atmospheric nitrogen fixation and phosphate solubilization in the rhizosphere soils of the test crop. The greater microbial activities subsequently augmented the mineralization and availability of nitrogen and phosphorus in the soil solution, which in turn increased the yield of the crop. Among the herbicides, oxyfluorfen was most stimulative followed by fluchloralin and oxadiazon in augmenting the microbial activities in soil. Butachlor also accentuated the mineralization and availability of nitrogen due to higher incitement of non-symbiotic N(2)-fixing bacteria in paddy soil. The grain and straw yields of the crop were also significantly increased due to the application of oxyfluorfen (20.2% and 21%) followed by fluchloralin (13.1% and 15.4%) and butachlor (9.1% and 10.2%), respectively.     

Photochemical transformations of tetrabromobisphenol A and related phenols in water

A method was developed for studies of the phototransformation at UV irradiation of aqueous solutions of tetrabromobisphenol A (TBBPA), tribromobisphenol A (TriBBPA), tetrachlorobisphenol A (TCBPA), 2,4-dichlorophenol at various pHs as well as 2-chlorophenol, 2-bromophenol, 3,4-dichlorophenol and bisphenol A at pH 11. The absorbance spectra of the compounds and the emission spectra of the light-source were determined and used to calculate disappearance quantum yields of the photochemical reactions that were taking place. No major differences between the disappearance quantum yields of TBBPA and TCBPA were observed at pH 10, while the disappearance quantum yield of TriBBPA was approximately two times higher. The rate of decomposition of TBBPA was six times higher at pH 8 than at pH 6. Identification of the degradation products of TBBPA and TriBBPA, by GC-MS analysis and by comparison to synthesised reference compounds, indicated that TBBPA and TriBBPA decompose via different mechanisms. Three isopropylphenol derivatives; 4-isopropyl-2,6-dibromophenol, 4-isopropylene-2,6-dibromophenol and 4-(2-hydroxyisopropyl)-2,6-dibromophenol, were identified as major degradation products of TBBPA while the major degradation product of TriBBPA was tentatively identified as 2-(2,4-cyclopentadienyl)-2-(3,5-dibromo-4-hydroxyphenyl)propane.     

Retention capacity of an organic bio-mixture against different mixtures of fungicides used in vineyards

A laboratory experiment was carried out to test the efficiency of a bio-mixture made up of pruning residues at two (PR2) and five (PR5) years of composting and wheat straw (STW) in the biological cleaning of water contaminated by different mixtures of fungicides usually employed in vineyards. The experiment was conducted and reproduced at a scale of 1:100 of operating field conditions. Commercial formulates of penconazole (PC), (RS)-1-[2-(2,4-dichlorophenyl)pentyl]-1H-1,2,4-triazole), dimetomorph (DM), (EZ)-4-[3-(4-chlorophenyl)-3-(3,4-dimethoxyphenyl)acryloyl]morpholine), azoxystrobin (AZ), (methyl (E)-2-{2-[6-(2-cyanophenoxy)pyrimidin-4-yloxy]phenyl}-3-methoxyacrylate), iprovalicarb (IP), (isopropyl 2-methyl-1-[(RS)-1-p-tolylethyl]carbamoyl-(S)-propylcarbamate), metalaxyl (MX), (methyl N-(methoxyacetyl)-N-(2,6-xylyl)-DL-alaninate), fludioxonil (FL), (4-(2,2-difluoro-1,3-benzodioxol-4-yl)-1H-pyrrole-3-carbonitrile) and cyprodinil (CY), (4-cyclopropyl-6-methyl-N-phenylpyrimidin-2-amine) were mixed in water and discharged into the bio-mixture following the time schedule of the treatments carried out in the grapevine in real field conditions. At each treatment, contaminated water with fungicides was circulated repeatedly through the bio-mixture to enhance the sorption of fungicides. In fact, it retained them between 98–100% with the exception of MX of which it was able to retain only 90.5%. The adsorption/desorption experiment showed that repeated circulation of water, instead of enhancing MX retention, can easily remove about 30% of MX already adsorbed by the bio-mixture. This finding suggests that water contaminated by very mobile pesticides should be discharged at the end of field treatments without re-circulating the water in order to avoid the release of pesticides weakly adsorbed on the bio-mixture.     

Metolachlor persistence in laboratory and field soils under Indian tropical conditions

Metolachlor [2-chloro-N-(2-methoxy-1-methylethyl)-2'-ethyl-6'- methyl acetanilide] dissipation under both field and laboratory conditions were studied during summer season in an Indian soil. Metolachlor was found to have moderate persistence with a half-life of 27 days in field. The herbicide got leached down to 15-30 cm soil layer and residues were found up to harvest day of the sunflower crop in both 0-15 cm and 15-30 cm soil layers. Metolachlor was found to be more persistent in laboratory studies conducted for 190 days. The rate of degradation was faster in soil under flooded partial anaerobic conditions as compared to aerobic soil with a half-life of 44.3 days. In aerobic soil, metolachlor was very stable with only 49% dissipation in 130 days. Residues remained in both the soils up to the end of the experimental period of 190 days.     

Soil-catalyzed oxidation of aniline

Aniline partially degraded in sterile soil to azobenzene, azoxybenzene, phenazine, form=anilide, and acetanilide. Nitrobenzene, $\text{p}$-benzoquinone, and unidentified species were possible products; substantial bound residues may also have formed. Soil-catalyzed conversion of aniline or [$\text{d}$₅]aniline seems evidenced by 6-24X more product recovery in sterile soil than in sterile water alone, a process inhibited by Na₂S₂O₄. Freundlich adsorption constants showed: azobenzene > azoxybenzene > phenazine > aniline.     

Manganese peroxidase-catalyzed oxidative degradation of vanillylacetone

When 4-(4-hydroxy-3-methoxy-phenyl)-2-butanone (vanillylacetone) was tested for manganese peroxidase (MnP)-catalyzed oxidation, it was found to be degraded with the cleavage of an aromatic ring. Among numerous products of vanillylacetone oxidation, four major ones were purified by thin-layer chromatography and identified using mass spectroscopy (MS) and nuclear magnetic resonance (NMR) analysis. Three of them maintained the aromatic ring structure and were identified as 4-[6,2'-dihydroxy-5,3'-dimethoxy-5'-(3-oxo-butyl)-biphenyl]-butan-2-one, 4-(4-hydroxy-3-methoxyphenyl)-3-buten-2-one, and 4-[6,2'-dihydroxy-5,3'-dimethoxy-5'-(3-oxo-butyl)-biphenyl]-3-buten-2-one. Even though the fourth product could not be purified to a single compound, data from infrared spectroscopy showed that it did not have a benzene ring. From MS and NMR analysis, 3-(3-oxo-butyl)-hexa-2,4-dienedioic acid-1-methyl ester was tentatively suggested as the dominant species. The reaction mechanism was suggested on the basis of the structural information of these products. To our knowledge, this paper is the first report on aromatic ring cleavage of the phenolic compound by MnP.     

Acetamiprid, carbendazim, diuron and thiamethoxam sorption in two Brazilian tropical soils

Sorption of acetamiprid ((E)-N1-[(6-chloro-3-pyridyl)methyl]-N2-cyano-N1-methylacetamidine), carbendazim (methyl benzimidazol-2-ylcarbamate), diuron (N-(3,4-dichlorophenyl)-N, N-dimethyl urea) and thiamethoxam (3-(2-chloro-thiazol-5-ylmethyl)-5-methyl-[1,3,5]oxadiazinan-4-ylidene-N-nitroamine) was evaluated in two Brazilian tropical soils, Oxisol and Entisol, from Primavera do Leste region, Mato Grosso State, Brazil. To describe the sorption process, batch experiments were carried out. Linear and Freundlich isotherm models were used to calculate the K(d) and K(f) coefficients from experimental data. The K(d) values were utilized to calculate the partition coefficient normalized to soil organic carbon (K(oc)). For the pesticides acetamiprid, carbendazim, diuron and thiamenthoxan the K(oc) (mL g(- 1)) values ranged in both soils from 98 - 3235, 1024 - 2644, 145 - 2631 and 104 - 2877, respectively. From the studied pesticides, only carbendazim presented correlation (r(2) = 0.82 and p < 0.01) with soil organic carbon (OC) content. Acetamiprid and thiamethoxam showed low sorption coefficients, representing a high risk of surface and ground water contamination.     

Photolysis of the herbicide bispyribac sodium in aqueous medium under the influence of UV and sunlight in presence or absence of sensitizers

The photolysis of a rice herbicide Bispyribac sodium (Sodium 2, 6-bis [(4, 6-dimethoxypyrimidin-2-yl) oxy] benzoate) has been studied in different aqueous medium (distilled water, pond water and Irrigation water) under the influence of UV (λ max ≥ 250 nm) and sunlight in presence or absence of sensitizers (TiO₂ and KNO₃). The study was conducted under laboratory simulated condition which made it possible to evaluate the contribution of different factors viz. source of irradiation, solvent and sensitizers towards the photolysis of bispyribac sodium. The photodegradation proceeds via first order reaction Kinetics in all the cases. Five photo metabolites (M₁-M₅) were isolated in pure form by column chromatographic method from the irradiation system under UV influenced and TiO₂ as sensitizer. From the different spectral data (IR, NMR, UV-VIS, Mass) the structure of these five metabolites were assigned as M₁ (Phenol), M₂ [2, 6-Dihydroxy benzoic acid], M₃ [2, 6-bis [(4, 6 dimethoxypyrimidin-2yl) oxy] benzoic acid], M₄ [2-(3-Hydroxy-phenoxy)-pyrimidine-4, 6-diol] and M₅ as [2,4-Dihydroxy-3, 5-dimethoxy-6-(4-methoxy pyrimidine-2-yloxy)-benzoic acid]. Moreover, another six photometabolites (M₆-M₁₁) were identified from the different irradiation system on the basis of Micromass analysis. On the basis of MS/MS data analysis, the structure of these six photometabolites were assigned as M₆ [2-(4, 6-Dimethoxy-pyrimidin-2-yloxy)-6-hydroxy-benzoic acid], M₇ [2-Hydroxy-6-(4-hydroxy-6-methoxy-pyrimidin-2-yloxy)-benzoic acid], M₈ [4, 6-Dimethoxy-pyrimidin-2-ol], M₉ [6-Methoxy-pyrimidine-2, 4-diol], M₁₀ [2-Hydroxy-6-(pyrimidin-2-yloxy)-benzoic acid] and M₁₁ [2, 4, 6-Trimethoxy-pyrimidine]. The plausible Photodegradation pathways of bispyribac sodium in the present investigation were portrayed which proceeds via hydrolysis, hydrolytic cleavage, O-dealkylation, decarboxylation, dehydroxylation, O-alkylation and hydroxylation.     

Fate of isoxaben in a containerized plant rhizosphere system

Commercial production of ornamental plants is an important industry in the United States and involves a complex technology that includes the use of herbicides. Isoxaben[N-[3-(1-ethyl-1-methylpropyl)-5-isoxazolyl]-2,6-dimethoxybenzamide] is a pre-emergence herbicide used for controlling weeds in many areas including containerized ornamental plants. Degradation was studied in potting mix (80% bark, 20% sand) with three different regimes (sterile, bulk and rhizosphere). The rhizosphere regime contained Switch Grass (Panicum virgatum), and plants were allowed to grow for 14 days before adding isoxaben (10 microg/g potting mix). Isoxaben was degraded to 0.5 microg/g in 60 days giving a half-life of 7 days. Two degradation products were detected: 3-nitrophthalic acid in the rhizosphere and bulk regimes and 4-methoxyphenol in the sterile regime. Microbial population shifts were determined by fatty acid methyl ester profile analysis and were influenced by the introduction of a plant (rhizosphere regime) and by isoxaben addition.     

Influence of fenamidone, indoxacarb, pyraclostrobin, and deltamethrin on the population of natural yeast microflora during winemaking of two sardinian grape cultivars

The influence of fenamidone ((S)-1-anilino-4-methyl-2-methylthio-4-phenylimidazolin-5-one), pyraclostrobin (methyl 2-[1-(4-chlorophenyl)pyrazol-3-yloxymethyl]-N-methoxycarbanilate), indoxacarb (methyl 7-Chloro-2,5-dihydro-2-[[(methoxycarbonyl) [4- (trifluoromethoxy) phenyl] amino] carbonyl] indeno[1,2-e][1,3,4] oxadiazine-4a(3H)-carboxylate), and deltamethrin ([cyano-[3-(phenoxy)phenyl]methyl] 3-(2,2-dibromoethenyl)-2,2-dimethylcyclopropane-1-carboxylate) on spontaneous fermentation carried out by natural yeast grapes microflora, was studied during the wine-making process. Aliquots of pesticide standard solutions were added to the grapes before crushing, to reach a concentration equal or half the maximum residue limit (MRL). Vinifications were performed, with maceration (R), or without maceration (W). During the wine-making process, samples were taken at the beginning (one hour after grapes crushing), at the middle and at the end of the spontaneous fermentation process. At half the MRL concentration, deltamethrin affected Pichia sp. population with a decrease of almost 50 %, while fenamidone decreased Candida sp., Candida stellata at 83, and 36%, respectively. Metschnikowia pulcherrima population decreased in all samples when compared to the control. Experiments at MRL levels showed a strong reduction for all non-Saccharomyces yeast species, when grapes had been treated with pyraclostrobin, fenamidone, and deltamethrine, except for Candida sp. which was found to have been affected only by fenamidone residues. Growth zone inhibition test showed only an in vitro activity of pyraclostrobin over Kloeckera spp., C. stellata, and M. pulcherrima. Microvinification experiments produced wines with no differences concerning S. cerevisiae population as well as production of ethanol and residual sugars. Experiments showed that at the end of the fermentation process pesticides were adsorbed by the lees and grape skins, and no pesticides residue was detectable in wine.     

Degradation of isoxaben in soils and an aqueous system.

The degradation of isoxaben [N-[3-(1-ethyl-1-methylpropyl)-5-isoxazolyl]-2,6-dimethoxybenzamide] was studied in soil and in an aqueous system. Soil studies were conducted in Erlenmeyer flasks (treated with 1 microg/g isoxaben) and mineralization studies in Biometer flasks (treated with 1 microg/g unlabeled and 14C-isoxaben) incubated at 23 C. Degradation in the aqueous system was performed in Erlenmeyer flasks under aerobic and anaerobic conditions incubated at 23 degrees C. Incubation mixtures were extracted at selected times and analyzed for isoxaben and degradation products by HPLC with product identification confirmed by GC-MS. After 8 weeks, 78% and 23% of the total isoxaben disappeared in nonsterile and sterile soils, respectively. After 12 weeks, approximately 1% of the labeled isoxaben was recovered as CO2 in the Biometer flask experiments; no volatile products were detected, and 5% and 33% of the total radioactivity was recovered from the nonsterile and sterile soils, respectively. In the aquatic system after 8 weeks, isoxaben had decreased from 1microg/g to 0.1 and 0.004 microg/g under aerobic and anaerobic conditions, respectively. Degradation products detected from the soil studies were 3-nitrophthalic acid and 4-methoxyphenol, and 3-nitrophthalic acid in the aqueous system studies. Microbial activity was considered to be a major factor in the degradation of isoxaben in this study.     

Translocation and persistence of EDU (ethylenediurea) in plants: the relationship with its role in ozone damage

Bean plants (Phaseolus vulgaris L. cv Lit) were treated with N-[2-(2-oxo-1-imidazolinidyl)ethyl]-N'-phenylurea (EDU) (150 microg ml(-1)) in hydroponic conditions. The EDU concentration in different plant tissues was measured by HPLC. EDU accumulated in leaves and persisted for more than 10 days showing a slow degradation. Using five different EDU concentrations, a significant relationship between EDU concentration in nutrient solution, ozone tolerance and EDU concentration in leaves was shown. Leaves which contained more EDU were less sensitive to ozone damage. Investigations on protoplasts and cell cultures showed that EDU did not enter the cells. Possible implications of EDU accumulation in the leaf apoplast are discussed.     

Synthesis and tentative identification of novel polybrominated diphenyl ether metabolites in human blood

Hydroxylated polybrominated diphenyl ethers (OH-PDBEs) are exogenous, bioactive compounds that originate, to a large extent, from anthropogenic activities, although they are also naturally produced in the environment. In the present study nine new authentic OH-PBDE reference standards and their corresponding methyl ether derivatives (MeO-PBDEs) were synthesised and characterised by NMR spectroscopy and mass spectrometry. Seven of the authentic reference standards prepared were thereafter tentatively identified in a pooled human blood sample. The tentatively identified OH-PBDEs were 3-hydroxy-2,2',4,4',6-pentabromodiphenyl ether, 3'-hydroxy-2,2',4,4',6-pentabromodiphenyl ether, 3-hydroxy-2,2',4,4',5-pentabromodiphenyl ether, 3-hydroxy-2,2',4,4',5,6'-hexabromodiphenyl ether, 3'-hydroxy-2,2',4,4',5,6'-hexabromodiphenyl ether, 3-hydroxy-2,2',4,4',5,5'-hexabromodiphenyl ether and 4-hydroxy-2,2',3,4',5,5',6-heptabromodiphenyl ether. An additional seven OH-PBDEs were tentatively identified in the pooled human blood sample, of which one OH-PBDE, 4'-hydroxy-2,2',4,5,5'-pentabromodiphenyl ether, has not been identified in human blood before. The identification was performed using gas chromatography-mass spectrometry (GC-MS) recording the bromine ions m/z 79, 81. The tentative identification was supported by the peaks relative retention times (RRTs) compared to authentic references on two GC columns of different polarities for the hexa-, and heptabrominated OH-PBDEs, and three different GC columns for the pentabrominated OH-PBDEs. The OH-PBDE congeners most likely originate from human metabolism of a flame retardant, i.e. polybrominated diphenyl ethers (PBDEs), due to the relatively high concentrations of PBDEs in the same human blood sample and the fact that these PBDEs could form the tentatively identified OH-PBDEs via metabolic direct hydroxylation or via 1,2-shift.