O-phenylphenol Research Articles

Determination of ammonium in seawater based on the indophenol reaction with o-phenylphenol (OPP)

A method for the determination of ammonium in seawater is described. The method is based on the indophenol (or the Berthelot) reaction with o-phenylphenol [(1,1′-biphenyl)-2-ol, abbreviated as OPP] as an alternative of phenol. Unlike phenol, OPP is available as stable flaky crystal with no caustic odor. This nature of OPP can eliminate much of the inconvenience associated with the use of phenol. The sensitivity of detection is comparable to that of the common phenol-based methods. The indophenolic compound obtained from the reaction with OPP is more hydrophobic than that from the reaction with phenol. Thus the indophenolic compound can be extracted directly from the alkaline reaction solution of the present method either with organic solvent or with reversed-phase column. The extracted indophenol can be used to recover ammonium nitrogen for the determination of 15-N isotope ratio. The experimental procedure of the extraction of indophenolic compound is relatively simple compared to the other existing methods.

Cytotoxic effects of postharvest fungicides, [formula omitted]-Phenylphenol, thiabendazole and imazalil, on isolated rat hepatocytes

The cytotoxic effects of ortho -phenylphenol (OPP), imazalil (IMZ) and thiabendazole (TBZ) on isolated rat hepatocytes were investigated. Addition of IMZ and OPP to hepatocyte suspensions at a concentration of 0.75 mM resulted in acute cell death, accommpanied by depletion of intracellular levels of glutathione and protein thiols. Both compounds rapidly depleted cellular ATP which consistently preceded the cell death. In addition, the cell death caused by IMZ was accompanied by the accumulation of intracellular malondialdehyde, indicating initiation of lipid peroxidation. During a 3-hr incubation period, TBZ did not affect these parameters. In mitochondria isolated from rat liver, IMZ and OPP impaired respiration related to oxidative phosphorylation. Based on these results, the order of toxic potency is IMZ > OPP > TBZ.

Liquid Chromatographic Determination of Phenolic Compounds in Hospital Disinfectant Products

Abstract A liquid chromatographic method has been developed to quantify phenolic compounds in various hospital disinfectant products. Each product contained two of the following three phenols: o-phenylphenol (OPP), p-tert-amylphenol (PTAP), and o-benzyl-p-chlorophenol (OBPCP). An isocratic mobile phase consisting of methanol and phosphate buffer was used in conjunction with a 5 cm column, which contained 3 micron C-18 packing material, to enact the separation of the phenolic compounds from each other and from product matrix components. Calibration curve data were generated for each phenolic compound to demonstrate linear response over the concentration range of interest. Spiked sample recovery studies were performed to assess the accuracy of the method for the analysis of the phenolic compounds in various product matrices. Finally, photodiode array generated spectra were used to demonstrate the homogeneity of the phenolic compound peaks.

Determination of Imazalil, Diphenyl, Thiabendazole and o-Phenyphenol in Citrus Fruits, and of Imazalil and Thiabendazole in Banana, by High Performance Liquid Chromatography.

Analytical methods for the determination of imazalil, thiabendazole (TBZ), diphenyl (DP) and o-phenylphenol (OPP) in citrus fruits and for the determination of TBZ and imazalil in banana were described. The four fungicides were simultaneously extracted with ethylacetate, and distributed into two fractions, namely, the imazalil and TBZ fraction and the DP and OPP fraction, by a liquid-liquid partitioning process for cleanup. The fungicides in each fraction were chromatographed on a J'sphere ODS-M80 column with acetonitrile-methanol-water mixture (47 : 13 : 40) adjusted pH to 2.4 containing 0.01 M sodium dodecyl sulfate as mobile phase. Detection of DP, OPP and TBZ derived from citrus fruits were carried out by fluorescence detector set at Ex. 285 nm and Em. 340 nm, and imazalil derived from citrus fruits was detected by UV spectrophotometric detector set at 220 nm. Detection of TBZ and imazalil derived from banana, the former was detected at Ex. 305 nm and Em. 350 nm and the latter was detected at UV 220 nm. Recoveries of DP, OPP, TBZ and imazalil from citrus fruits spiked at 20 μg/g of DP and 2.0 μg/g of others were 77.3-81.9%, 84.8-91.8%, 80.1-85.9% and 79.2-81.3%, respectively, and recoveries of TBZ and imazalil from banana spiked at 2.0 μg/g were 80.2% and 78.7%, respectively. The detection limits of DP, OPP, TBZ and imazalil in citrus fruits were 0.5, 0.05, 0.02 and 0.05 μg/g, respectively, and the detection limits of TBZ and imazalil in banana were 0.005 and 0.02 μg/g, respectively.

Azidopentaammine cobalt(III) complex: a selective photo-oxidant of ortho-phenylphenol in aqueous solution

Excitation of azidopentaammine cobalt(III) ([Co(NH 3) 5N 3] 2+), in the presence of ortho-phenylphenol (OPP) in neutral solution, leads to the disappearance of OPP and the formation of Co(II). The presence of OPP does not affect the initial quantum yields significantly. No oxygen effect is observed. Flash photolysis and electron spin resonance (ESR) spectroscopy provide evidence for the formation of azide (N 2 .) and ortho-phenylphenoxyl (OPP .) radicals. Cobalt(II) plays the role of a stabilizer for OPP . radicals. At high conversion, a brown precipitate is formed. Various analytical results (high performance liquid chromatography (HPLC), nuclear magnetic resonance (NMR) spectroscopy, mass spectometry) show that the “para-para” and “ortho-ortho” dimers of OPP are the major photoproducts. Trimers and tetramers are also obsrved as minor photoproducts. There is no formation of quinone derivatives.

Initiating activity of quinones in the two-stage transformation of BALB/3T3 cells.

2-tert-Butyl-1,4-benzoquinone (BQ), a metabolite of the rodent carcinogen 3-tert-butyl-4-hydroxyanisole (3-BHA), has been shown previously to have initiating activity for cell transformation. In this paper, we examined the initiating activity of quinones in a two-stage transformation assay using BALB/3T3 cells. Cells were treated first with a quinone and then with the tumor promoter 12-O-tetra-decanoylphorbol-13-acetate (TPA). The quinones tested were 1,4-benzoquinone (pQ), phenyl-1,4-benzoquinone (PhQ), menadione and 2,5-di-tert-butyl-1,4-benzoquinone (DBQ) in addition to BQ. pQ is a metabolite of benzene and phenacetin, and PhQ is a metabolite of o-phenylphenol (OPP) and sodium o-phenylphenate (OPP-Na). All of the tested quinones induced transformation in the presence of TPA but not in its absence. The extent of transformation caused by quinones followed by TPA was weak but statistically significant. Thus these quinones were shown to act as initiators in the transformation of BALB/3T3 cells. This result suggests that BQ, pQ and PhQ may be involved in carcinogenesis by 3-BHA, benzene, phenacetin, OPP and OPP-Na in vivo. Menadione has been reported to cause cytotoxic effects and mutations through active oxygen generation from semiquinone radicals. DBQ has two bulky substitutes which interfere with covalent bonds with DNA. Menadione and DBQ exhibited initiating activity in the present study. This result suggests that active oxygens generated from semiquinone radicals may play a role in the initiation of cell transformation.

Formation of 8-hydroxydeoxyguanosine in calf thymus DNA treated in vitro with phenylhydroquinone, the major metabolite of O-phenylphenol.

The generation of 8-hydroxydeoxyguanosine (8OHdG) in calf thymus DNA treated with O-phenylphenol (OPP) or its major metabolites, phenylhydroquinone (PHQ) and phenylbenzoquinone (PBQ), was studied. The content of 8OHdG residues was increased in DNA treated with PHQ, and the generation of 8OHdG was highly dependent on PHQ concentration. PBQ had little effect on the formation of 8OHdG, and OPP had no effect. The formation of 8OHdG by PHQ was reduced by oxygen radical scavengers such as catalase, sodium benzoate and sodium azide. The PHQ-induced 8OHdG formation was accelerated by the addition of CuCl or CuCl2 to the reaction mixture, but was decreased by the addition of chelating agents such as EDTA, bathocuproinedisulfonic acid disodium salt (bathocuproine disulfonate) and O-phenanthroline. These results demonstrate that hydroxyl radicals generated in the process of oxidation of PHQ contribute to the formation of 8OHdG in DNA, and copper ions facilitate the oxidative DNA damage. Copper ions greatly accelerated the PHQ-induced DNA cleavage in vitro, although they had no effect on cleavage without PHQ. On the other hand, DNA cleavage occurred by the addition of FeCl2 in the absence and presence of PHQ. FeCl2 stimulates 8OHdG formation only slightly with or without PHQ. Furthermore, the stimulatory effect of FeCl2 on 8OHdG formation was observed even in the presence of EDTA. The formation of 8OHdG in bladder DNA is likely to be one of a series of events leading to bladder tumors seen in rats fed OPP-containing diet.

Genotoxic effects of the o-phenylphenol metabolites phenylhydroquinone and phenylbenzoquinone in V79 cells

o-Phenylphenol (OPP) and its sodium salt, sodium o-phenylphenate are broad spectrum fungicides and disinfectants with widespread usage. Both chemicals have been reported to induce cancer in the kidney and urinary bladder of Fischer 344 rats. Recently it has been proposed that the metabolic activation of OPP occurs via a two-step process involving the cytochrome P450-mediated formation of phenylhydroquinone (PHQ) in the liver and a prostaglandin H synthase-mediated oxidation of PHQ to phenylbenzoquinone (PBQ) in the urinary tract. In order to further investigate the metabolic activation and genotoxic effects of OPP, we have investigated the ability of PHQ and PBQ to induce micronuclei and mutations at the HGPRT locus in a prostaglandin H synthase-containing V79 Chinese hamster lung fibroblast cell line. In arachidonic acid-supplemented V79 cells, PHQ induced a significant increase in micronuclei whereas no increase was observed in cells in the absence of arachidonic acid supplementation. Immunofluorescent labeling of centromeric proteins with the CREST antibody indicated that the arachidonic acid-dependent induction of micronuclei by PHQ was due almost entirely to micronuclei containing whole chromosomes which had failed to segregate properly during mitosis. The induction of micronuclei by PHQ was significantly inhibited by treatment of the cells with indomethacin, aspirin, ascorbic acid, dithiothreitol and reduced gluthathione supporting a role for prostaglandin H synthase in the genotoxic effects of PHQ. No increase in 6-thioguanine-resistant cells was observed in cells treated with PHQ or PBQ. This arachidonic acid-dependent conversion of PHQ to a genotoxic species is consistent with the hypothesis that a prostaglandin H synthase-mediated activation of PHQ may be involved in OPP- and SOPP-induced urinary tract carcinogenesis and also suggests that the induction of aneuploidy may play an important role in OPP-induced tumorigenesis.

Effect of scavengers of active oxygen species on cell damage caused in CHO-K1 cells by phenylhydroquinone, an o-phenylphenol metabolite

Phenylhydroquinone (PHQ), a metabolite of o-phenylphenol (OPP), is easily autoxidized to phenylbenzoquinone (PBQ), via the semiquinone (phenylsemiquinone, PSQ) with concomitant production of superoxide anion radicals (O 2 • ). We have used scavengers of active oxygen species to examine whether or not O 2 • produced during oxidation of PHQ is related to cell damage in CHO-K1 cells. PHQ at 10 γg/ml (3-h treatment) induced sister-chromatid exchange (SCE), endoreduplication (ERD) and cell-cycle delay in CHO-K1 cells. These effects were inhibited by catalase (280 U/ml), a scavenger of hydrogen peroxide (H 2O 2), as well as by the reductants, ascorbate (3mM) and GSH (1 mM). Mannitol (50 mM), a scavenger of hydroxyl radical (OH ., was ineffective and superoxide dismutase (SOD, 150 U/ml), a scavenger of O 2 • , or SOD plus catalase rather intensified the toxicity as did aminotriazole (20 mM), an inhibitor of catalase. Analyses of incubation solutions by HPLC showed that the extent of cell damage is correlated with PHQ loss; catalase suppressed PHQ loss, whereas SOD promoted it. The correlation was more clearly seen in the time courses of cell death and PHQ loss during incubation of PHQ with each of the scavengers of active oxygen species. These results show that neither O 2 • nor OH . participates in the cell damage, but rather H 2O 2 generated via dismutation of O 2 • may participate, probably by accelerating the autoxidation of PHQ and thus causing an increase in the production of toxic intermediates. In fact, conversion of PHQ to PBQ, a reactive product, was demonstrated during incubation with PHQ in phosphate-buffered saline by following the changes in UV-visible spectra of PHQ. Inclusion of H 2O 2 (0.2 or 1 mM) in the incubation mixture accelerated the PHQ loss. The present results can be explained in terms of the autoxidation mechanism of hydroquinone proposed by O'Brien (1991). Different from the results in the absence of S9 mix, the cell damage induced by 50 γg/ml OPP in the presence of S9 mix was not influenced by any of the scavengers of active oxygen species used. We conclude that PHQ causes cytotoxic and genotoxic effects through its autoxidation, both enzymatic and nonenzymatic, and that reactive intermediate(s) such as PSQ and/or PBQ may be ultimately responsible for the effects. H 2O 2 formed during the oxidation process participates in the damaging effects caused in the absence of S9 mix, probably by accelerating the autoxidation.

Simultaneous determination of carbaryl and o-phenylphenol residues in waters by first-derivative synchronous solid-phase spectrofluorimetry

A spectrofluorimetric method for the simultaneous determination of carbaryl (CBL) and o-phenylphenol (OPP) residue mixtures in waters has been developed. Carbaryl was hydrolysed in alkaline medium to give 1-naphthol. This compound and o-phenylphenol were fixed on QAE Sephadex A-25 gel at pH 10.75. The fluorescence of the gel, packed in a 1-mm silica cell, was measured directly with a solid-surface attachment. Overlapping of conventional fluorescence spectra is resolved by using first-derivative synchronous spectrofluorimetry and allows for the complete resolution of the mixture. The range of application is between 0.4 and 25.0 ng/ml for OPP and 0.8 and 25.0 ng/ml for CBL. The detection limits for o-phenylphenol and carbaryl were 0.1 and 0.2 ng/ml, respectively. The accuracy and precision of the method are reported. The method is suitable for determination of carbaryl and o-phenylphenol residues in natural waters. Recoveries from 95 to 105% have been obtained for natural waters spiked with CBL and OPP.

The effect of o‐phenyl phenol on the dyeing of an acrylic fiber with basic dyes

AbstractThe equilibrium uptake of o‐phenyl phenol onto Courtelle S at 98°C was found to follow a Nernst adsorption mechanism, indicating that uptake arises by virtue of hydrophobic interaction as well as ion–dipole, dipole–dipole, and dipole‐induced dipole forces operating between the fiber and the nonionic carrier. Differential scanning calorimetry was used to demonstrate the plasticizing action of the carrier on Courtelle S yarn. A linear relationship was obtained between the extent of plasticization, as measured by reduction in Tg of the fiber, and concentration of carrier applied to the fiber with the maximum extent of plasticization, showing a close correspondence to the aqueous solubility of o‐phenyl phenol at 98°C, the temperature at which the fiber was treated with the carrier. The relationship between the extent of enhancement of uptake of C. I. Basic Green 4 and C. I. Basic Red 13 onto Courtelle S yarn at 98°C and concentration of the carrier in the dyebath was also examined: The concentration of o‐phenyl phenol that gave maximum enhancement of dye uptake coincided with the aqueous solubility of the carrier at 98°C. © 1993 John Wiley & Sons, Inc.

Cytotoxic effects of biphenyl and hydroxybiphenyls on isolated rat hepatocytes

The cytotoxic effects of biphenyl (BP) and its hydroxylated derivatives, o-phenylphenol (OPP), m-phenylphenol (MPP), p-phenylphenol (PPP), 2-biphenylyl glycidyl ether (OPP-epoxide), phenyl-hydroquinone (PHQ), o, o′-biphenol ( o, o′-BPol) and p, p′-biphenol ( p, p′-BPol), were investigated in freshly isolated rat hepatocytes. OPP, MPP and PPP, at concentration of 0.75 mM, resulted in the loss of intracellular ATP, glutathione (GSH) and protein thiols, causing cell death. OPP-epoxide and BP were less toxic than the OPP isomers. MPP or PPP compared with OPP caused serious impairments in oxidative phosphorylation in mitochondria isolated from rat liver. PHQ (0.75 mM) caused a rapid loss of intracellular ATP which preceded the onset of cell death. PHQ was more toxic than o, o′-BPol or p, p′-BPol. PHQ dissolved in Krebs-Henseleit buffer without hepatocytes was rapidly converted to its corresponding quinone, phenyl-benzoquinone. The cytotoxicity produced by PHQ depends on the rate of formation of reactive intermediates. These results indicate that the addition of a hydroxyl group to the aromatic ring of BP enhances BP-induced cytotoxicity and that the mitochondria are a common target of the OPP isomers and other BP derivatives. In addition, the para- or meta-hydroxyl groups rather than the ortho-hydroxyl group increase the toxicity. The cytotoxicity produced by PHQ depends on the rate of formation of reactive intermediate(s) such as phenyl-benzoquinone.

Relationship between metabolism and cytotoxicity of ortho-phenylphenol in isolated rat hepatocytes

The relationship between the metabolism and the cytotoxicity of ortho-phenylphenol (OPP) was investigated using isolated rat hepatocytes. Addition of OPP (0.5–1.0 mM) to the hepatocytes caused a dose-dependent toxicity; 1.0 mM OPP caused acute cell death. Pretreatment of hepatocytes with SKF-525A (50 μM,a non-toxic level) enhanced the cytotoxicity of OPP (0.5–1.0 mM). This was accompanied by inhibition of OPP metabolism. Conversely, OPP at low concentrations (0.5 or 0.75 mM) was converted sequentially to phenyl-hydroquinol (PHQ) and then to glutathione (GSH) conjugate in the cells. The concentrations of both metabolites, especially PHQ-GSH conjugate, were very low in hepatocytes exposed to 1.0 mM OPP alone as well as with SKF-525A. The cytotoxicity induced by 0.5 mM OPP was enhanced by the addition of diethylmaleate (1.25 mM) which continuously depletes cellular GSH. In contrast, additions to hepatocytes of 5 mM of dithiothreitol, cysteine, N- acetyl- l- cysteine or ascorbic acid significantly inhibited the cytotoxicity induced by 0.5 mM PHQ; GSH, protein thiols and ATP losses were also prevented. Further, these compounds depressed the rate of PHQ loss in hepatocyte suspensions. These results indicate that the acute cytotoxicity caused by the high dose (1.0 mM) of OPP is associated with direct action by the parent compound; at low doses (0.5–0.75 mM) of OPP, the prolonged depletion of GSH in hepatocytes enhances the cytotoxicity induced by PHQ.

Fungicide application in water and in wax for decay control in ‘Galia’ melons

Abstract ‘Galia’ melons (Cucumis melo cv. Reticulatus) exported from Israel to Europe, are treated with 2000 ppm imazalil. The fungicide is incorporated in the wax used to coat the melon. This treatment protects the fruit against decay caused by Alternaria alternata and Fusarium spp., and leaves a residue of 4–5 ppm imazalil in the fruit. This amount exceeds the tolarance of some European countries who allow a residue below 0.5 ppm. To overcome this problem, other application methods were tested. Dipping or spraying the melons with 250 ppm imazalil in water followed by waxing, was as effective as the standard treatment while leaving a residue of 0.5 ppm. Testing other fungicides such as prochloraz and orthophenylphenol (OPP) confirmed that much smaller amounts are needed for decay control when applied in water.

Chronic Toxicity Test of o-Phenylphenol and Thiabendazole by Simultaneous Administration to Mice

o-Phenylphenol (OPP) and thiabendazole (TBZ), which are fungicides, have been approved as food additives in Japan. OPP induces urinary bladder tumor and renal lesions in rats but not in mice. TBZ has an enhancing effect on urinary bladder carcinogenesis induced by OPP in rats. The present study was performed to examine the combined effects of OPP and TBZ on mice. Groups of 20 male Crj: B6C3F1, mice were fed the basal diet (control, group C), diet containing 0.2% TBZ (group T), 0.65% OPP (group O-1), 1.3% OPP (group O-2), 2.6% OPP (group O-3), 0.65% OPP plus 0.2% TBZ (group OT-1), 1.3% OPP plus 0.2% TBZ (group OT-2) or 2.6% OPP plus 0.2% TBZ (group OT-3) for 52 weeks. The survival rates were 100% (20/20), 90% (18/20), 100% (20/20), 95% (19/20), 100% (20/20), 90% (18/20), 75% (15/20) and 70% (14/20) in group C, T, O-1, O-2, O-3, OT-1, OT-2 and OT-3, respectively. The treated groups suffered growth retardation throughout the study. The kidney weights showed a dose-related decrease in the O and OT groups. No treatment-related increase in tumor formation of any organ or tissue was observed. Dose-related increases were observed in the incidences of degenerative and necrotic changes in tubular epithelium and transitional cells of the kidney, and of anisonucleosis and pigmentation in liver cells in the O and OT groups. Under the experimental conditions employed, OPP plus TBZ induced no urinary bladder tumor in mice.

Examination of microsomal cytochrome P450-catalyzed in vitro activation of o-phenylphenol to DNA binding metabolite(s) by 32P-postlabeling technique.

It has been previously reported that the reactive metabolites phenylsemiquinone and phenylbenzoquinone are generated during microsomal cytochrome P450-catalyzed redox cycling of o-phenylphenol (OPP). However, covalent modification of DNA by OPP-reactive metabolites has yet not been demonstrated. In the present study we have investigated the covalent binding in DNA by OPP-reactive metabolites using 32P-postlabeling. Analysis of adducts by 32P-postlabeling in products of chemical reaction of DNA with phenylbenzoquinone revealed four major and several minor adducts. The chemical reaction of deoxyguanosine 3'-phosphate with phenylbenzoquinone also showed four major adducts. The chromatographic mobility of major adducts of deoxyguanosine 3'-phosphate-phenylbenzoquinone was identical to that of major adducts of DNA-phenylbenzoquinone. The major adducts are demonstrated to be stable. The total covalent binding in deoxyguanosine 3'-phosphate by phenylbenzoquinone (686,000-687,000 amol/nmol nucleotide) was higher than that observed in DNA (26,500-28,000 amol/nmol nucleotides). Reaction of DNA with OPP or a hydroxylated metabolite of OPP, phenylhydroquinone, in the presence of microsomes and NADPH or cumene hydroperoxide showed four major adducts. Adduct formation in DNA by OPP or phenylhydroquinone in the presence of the microsomal activation system was drastically decreased by known inhibitors of cytochrome P450. The chromatographic mobility of major adducts in DNA by OPP or phenylhydroquinone in the presence of microsomal activation system matched with those major adducts observed in deoxyguanosine 3'-phosphate or DNA reacted with pure phenylbenzoquinone. These data demonstrate that OPP or phenylhydroquinone, a hydroxylated metabolite of OPP, is able to bind covalently to DNA in the presence of a microsomal cytochrome P450 activation system. Phenylbenzoquinone is one of the DNA-binding metabolite(s) of OPP. It is concluded that OPP is genotoxic in an in vitro system and genotoxicity produced by OPP-reactive metabolites may play a role in OPP-induced cellular toxicity or cancer.

DNA adduct formation by o-phenylphenol metabolite in vivo and in vitro.

[U-14C]o-Phenylphenol (OPP) was found to bind covalently to calf thymus DNA during a 60 min incubation in the presence of microsomes, but not in their absence, indicating that metabolic conversion of the parent compound, OPP, to an activated form is essential. Postlabeling analysis with bladder DNA of rats fed a diet containing 2% OPP for 13 weeks revealed one major adduct on TLC. In an in vitro postlabeling experiment with calf thymus DNA, both of the major metabolites of OPP, phenylhydroquinone (PHQ) and phenylbenzoquinone (PBQ), formed adducts, but no adducts were observed with OPP. The chemical structure responsible for adduct formation is thought to be the PHQ semiquinone radical intermediate formed during interconversion between PHQ and PBQ. When the oligonucleotides, pd(A)12-18, pd(C)12-18, pd(G)12-18 and pd(T)12-18, were used in vitro, only pd(G)12-18 gave TLC-detectable adducts on treatment with PHQ and PBQ. The covalent binding appears to be rather specific to guanine residues. These results suggest that covalent binding of the OPP metabolite is one of the underlying events in OPP-induced carcinogenesis in rats.

Analysis of Post-Harvest Application Pesticides in Citrus Fruits

Analytical methods for 7 kinds of post-harvest application pesticides in citrus fruits and juices were established.Diphenyl (DP), o-phenylphenol (OPP) and 2, 4-D (2, 4-dichlorophenoxyacetic acid) were simultaneously extracted under acidic conditions, and thiabendazole (TBZ), imazalil, benomyl and sec-butylamine were simultaneously extracted under basic conditions. DP, OPP and 2, 4-D were determined by GC/MS (SIM) and imazalil, TBZ, benomyl and sec-butylamine were determined by HPLC with a UV or fluorescence detector. Recoveries of the 7 kinds of post-harvest application pesticides in lemon and lemon juice were 60.0-104.8% and 67.3-96.2%, respectively. Detection limits in citrus fruit and juice were 0.005-0.05ppm and 0.001-0.01ppm, respectively.

Residues of Post-Harvest Application Pesticides in Citrus Fruits after Storage and Processing into Lemon Marmalade

The residue levels of 8 pesticides in post-harvest-treated citrus during storage and processing into marmalade were investigated. Lemons, oranges and grapefruits were dipped in a solution of diphenyl (DP), o-phenyl phenol (OPP), 2, 4-dichlorophenoxyacetic acid (2, 4-D), imazalil, thiabendazole (TBZ), benomyl and sec-butylamine (BA), or fumigated with methyl bromide, and stored at 14°C followed by determination of residue levels at intervals of several days. As the result of 91 days' observation, the half lives of pesticides ranged from 36 days to in excess of 6 months. DP and imazalil were extremely stable and bromide gradually increased in the citrus fruits. On the 8th week of storage, lemons were processed into marmalade and the levels of pesticides were determined after each step. In the final product marmalade, 95% of DP, 41% of OPP, 42% of imazalil and 22% of bromide were found (ratio to initial contents), while no 2, 4-D, TBZ, benomyl or BA was detected.

Metabolism of phenylhydroquinone by prostaglandin (H) synthase: possible implications in o-phenylphenol carcinogenesis

o-Phenylphenol (OPP) and its sodium salt sodium ortho-phenylphenate (NaOPP) are broad spectrum fungicides and antibacterial agents. Both are urinary bladder and renal carcinogens in the Fischer 344 rat. OPP is converted by mixed-function oxidases in the liver to phenylhydroquinone (PHQ). Since appreciable amounts of prostaglandin (H) synthase (PGS) are found in rat bladder and kidney-medullary papilla, the target sites of OPP- and NaOPP-induced tumors, we hypothesized that a secondary PGS-mediated activation of PHQ to phenylbenzoquinone (PBQ) may occur in the bladder and kidney. We have studied the metabolism of PHQ by PGS in the presence of arachidonic acid and hydrogen peroxide as co-factors. These studies showed that PHQ is indeed metabolized to a product having identical spectral and electrochemical properties to PBQ. The disappearance of PHQ with time was stoichiometric to the formation of PBQ. Less than 10% of PHQ was converted to PBQ in the absence of enzyme, indicating that auto-oxidation may play only a minor role in the conversion of PHQ to PBQ. Similar results were obtained when PGS was replaced with either myeloperoxidase or horseradish peroxidase and hydrogen peroxide as co-factor. These studies suggest that the peroxidative metabolism of PHQ by PGS to the reactive PBQ could play an important role in OPP-induced urinary bladder and kidney carcinogenesis in rats.