Phenylhydroquinone Research Articles

Depigmenting action of phenylhydroquinone, an O-phenylphenol metabolite, on the skin of JY-4 black guinea-pigs.

The effects of o-phenylphenol (OPP) and its metabolite, phenylhydroquinone (PHQ) on the skin of JY-4 black guinea-pigs were studied. Topical application of 1 or 5% PHQ on the black skin of the back caused marked depigmentation and hypopigmentation of the skin after 5 weeks, whereas OPP applied at the same concentrations had little effect. Depigmented skin had an increased L* (lightness) value in the CIE-L*a*b* color system. This corresponded with a decreased number of melanocytes and melanosomes in the melanocytes and keratinocytes, the disruption of melanosomes in the melanocytes, and destruction of the membranous organelles of the melanocytes. These morphological and numerical changes in epidermal melanocytes indicate that selective melanocyte toxicity occurred. Furthermore, application of PHQ to the skin of white guinea-pigs caused skin irritation, as shown by a colorimetric increase in a* value (redness) and by histological observation of inflammation. This study confirmed that OPP, which is a reported depigmenter, has little depigmenting action, while its metabolite, PHQ, is a potent depigmenter preferentially affecting melanocytes.

Photocatalytic degradation of 2-phenylphenol on TiO 2 and ZnO in aqueous suspensions

The degradation of 2-phenylphenol (OPP), commonly used as fungicide, can be photocatalysed by TiO 2 and ZnO. The latter is a little more efficient but cannot be used in acidic solution. In both cases, the main identified photoproducts are hydroquinone (HQ), p-benzoquinone (BQ), phenylhydroquinone (PHQ), phenylbenzoquinone (PBQ), 2,2′- and 2,3-dihydroxybiphenyls (2,2′- and 2,3-BPh(OH) 2). The observed minor formation of 2-hydroxydibenzofuran is due to the photocyclisation of PBQ. The influence of various parameters is considered. The phototransformation of OPP is slightly favoured by increasing pH. It is enhanced by the addition of small amounts of H 2O 2, but it is inhibited by high concentrations of chloride, sulphate or nitrate. From the inhibiting effect of alcohols, it is deduced that the main degradation pathway involves hydroxyl radicals, but a direct oxidation by positive holes h + is probably not negligible. The observed slow photodegradation of ZnO in unbuffered solution is attributed to an electrochemical process. A mechanism is proposed for the photocatalytic transformation of OPP.

Orthophenylphenol and phenylhydroquinone residues in citrus fruit and processed citrus products after postharvest fungicidal treatments with sodium orthophenylphenate in California and Florida.

Sodium orthophenylphenate (SOPP) has been used extensively for >40 years to control postharvest diseases of citrus fruits. Studies of the metabolism of [(14)C]SOPP have identified orthophenylphenol (OPP) as the major metabolite with phenylhydroquinone (PHQ) as a minor metabolite. The whole-fruit tolerance in the United States for OPP is 10 ppm. This study was conducted to quantify terminal OPP and PHQ residues in whole Navel oranges, grapefruit, and lemons following SOPP applications at maximum application rates and following commercial application and fruit storage practices. OPP and PHQ residues also were determined in products processed from treated Navel oranges. OPP residues in lemons, Navel oranges, and grapefruit treated with SOPP using foamer wash and shipping wax applications remained below the 10 ppm tolerance, and PHQ residues were all < or =0.439 ppm. PHQ residues in whole fruit increased with time in commercial storage. OPP residues in all Navel orange matrices except oil remained relatively stable with time in commercial storage; residues in oil declined substantially while in storage.

Promoted random orientation of the phenyl substituent of phenylhydroquinone-terephthalic acid polyesters prepared with a diphenyl chlorophosphate/pyridine condensing agent

The reaction of sterically hindered hydroxyl groups at the 2-position of methylhydroquinone and phenylhydroquinone (PhHQ) to form esters was largely promoted by their slow addition to benzoic acid activated by diphenyl chlorophosphate in pyridine. A modification of this reaction was applied to the preparation of thermotropic terephthalic acid/PhHQ and 2,5-dichloroterephthalic acid/PhHQ polymers with randomly oriented phenyl substituents, and the properties of the polymers were studied in terms of their transition temperatures, which were determined by differential scanning calorimetry and microscopic observation. The melting points were lowered by about 30–50 °C by the dropwise addition of PhHQ over 10–30 min. The molecular structures of the 2,5-dichloroterephthalic acid/PhHQ polymers were studied by 13C NMR. © 2001 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 39: 1726–1732, 2001

Studies on the synthesis and properties of thermotropic liquid crystalline polycarbonates. VII. Liquid crystalline polycarbonates and poly(ester-carbonate)s derived from various mesogenic groups

Three series of thermotropic liquid crystalline polycarbonates and poly(ester-carbonate)s were prepared by solution polycondensation of 4,4′-biphenyldiol (BP), 4′-hydroxybiphenyl-4-hydroxybenzoate (HHB), or 4-hydroxyphenyl-4″-hydroxybiphenyl-4′-carboxylate (HHBP), as mesogenic unit, with 1,10-bis(p-hydroxybiphenoxy)decane (N10), bisphenol A (BPA), 4,4′-dihydroxy-diphenyl ether (BPO), 4,4′-[phenylbis(oxy)]bisphenol (BPOO), methylhydroquinone (MeHQ), or phenylhydroquinone (PhHQ). One series of cholesteric poly(ester-carbonate)s were also prepared by using HHBP, the aromatic diols mentioned above and isosorbide as the chiral moiety. All polycondensations were implemented in pyridine by using triphosgene as the condensation agent. The synthesized polycarbonates were characterized by viscometer, FTIR, DSC, TGA measurements, polarizing microscopy equipped with a heating stage, and WAXD powder pattern. In this study, it was found that the liquid crystalline properties of polycarbonates strongly rely on the mesogenic unit applied. HHBP-series exhibits a wide temperature region of liquid crystalline (LC) phase even with 50% of bisphenol A (BPA), which is a V-shaped structure and usually destroys liquid crystalline properties. In addition, homopolycarbonate with HHBP structure possesses extraordinarily low phase-transition temperature and wide liquid crystalline phase range, due to its asymmetric structure. This asymmetric structure results in head-to-tail, head-to-head, and tail-to-tail random conformation of polymer chain. The isosorbide containing poly(ester-carbonate)s formed cholesteric phase, which showed homogeneous blue, green, or red Grandjean texture upon shearing in molten state and the Grandjean texture could be frozen easily while quenching the sample to the room temperature. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 38: 1852–1860, 2000

The inhibition of phenylhydroquinone-induced oxidative DNA cleavage by constituents of Moutan Cortex and Paeoniae Radix.

Moutan Cortex (root cortex of Paeonia suffruticosa ANDREWS) and Paeoniae Radix (root of Paeonia lactiflora PALLAS) are crude drugs used in many traditional prescriptions and have constituents in common. We studied the effects of extracts of these crude drugs and their constituents on oxidative DNA damage caused by phenylhydroquinone (PHQ), a major metabolite of o-phenylphenol. Both drugs suppressed the cleavage of pUC18 DNA induced by PHQ, and scavenged the superoxide and hydroxy radical generated by the chemical. They also inhibited the oxidative DNA cleavage by tert-butylhydroquinone (TBHQ), one of the major metabolites of butylated hydroxyanisole. When constituents were examined with the same system, galloylpaeoniflorin and 1,2,3,4,6-penta-O-galloyl-beta-D-glucose (PGG) were found to be the most potent inhibitors of the DNA cleavage. These constituents had oxygen radical scavenging activity. Paeonol also attenuated the DNA cleavage. Paeoniflorin and albiflorin had relatively small inhibitory effects on DNA cleavage. However, catechin enhanced the PHQ-induced DNA cleavage. The suppression of oxidative DNA damage by Moutan Cortex and Paeoniae Radix might be attributable to the additive effects of galloylpaeoniflorin, PGG and other constituents.

LCP aromatic polyesters by esterolysis melt polymerization

Polyarylates have previously been synthesized from acetate esters via esterolysis (loss of methyl acetate). This polycondensation can be extended to p-substituted aromatic monomers for liquid crystal polyesters (LCPs). For AB-type polymers, methyl p-acetoxybenzoate and methyl 6-acetoxynaphthoate were copolymerized to an LCP with reasonable molecular weights. Benzoate esters, methyl 4-benzoyloxybenzoate (MBB) and methyl 6-benzoyloxy-2-naphthoate (MBN), are also investigated. Several tin and antimony oxide catalysts were effective. The rate of esterolysis polymerization of MBB and MBN is slower than that of the corresponding acidolysis melt polymerization, but fast enough to give relatively high-molecular-weight polymers and similar thermal stability as commercial LCP prepared by acidolysis. Using these alternative benzoyloxy groups significantly reduced the color problem, because ketene loss cannot occur. Esterolysis melt polymerizations leading to AB/AABB-type LCPs were performed using either dimethyl 2,6-naphthalene dicarboxylate (DMND) or dimethyl terephthalate (DMT) with methyl 4-acetoxybenzoate and phenylhydroquinone diacetate with tin and antimony catalysts. DMT-based monomer compositions show much faster polymerization than DMND-based compositions using antimony oxide catalyst. All these LCPs show a Tg in the 140–170 °C range as a result of the inclusion of the naphthalene and/or phenyl hydroquinone units in the polymer chain. Compositions completely off-balanced on either side still lead to relatively high-molecular-weight copolyesters because either excess monomer can be removed during polymerization. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 38: 3586–3595, 2000

Oxidative damage to cellular and isolated DNA by metabolites of a fungicide ortho-phenylphenol.

ortho-Phenylphenol (OPP) and its sodium salt, which are used as fungicides and antibacterial agents, have been found to cause carcinomas in the urinary tract of rats. To clarify the carcinogenic mechanism of OPP, we compared the DNA damage inducing ability of an OPP metabolite, phenyl-1,4-benzoquinone (PBQ) with that of another metabolite, phenylhydroquinone (PHQ). Pulsed field gel electrophoresis showed that PBQ and PHQ induced DNA strand breakage in cultured human cells, but PBQ did it more efficiently than PHQ. Significant increases in 8-oxo-7,8-dihydro-2'-deoxyguanosine (8-oxodG) were observed in cells treated with PBQ and PHQ, and the increase of 8-oxodG induced by PBQ was significantly higher than that induced by PHQ. Using 32P-5'-end-labeled DNA fragments obtained from human p53 tumor suppressor gene and c-Ha-ras-1 protooncogene, we showed that PBQ plus NADH, and also PHQ, induced DNA damage frequently at thymine residues, in the presence of Cu(II). The intensity of DNA damage by PBQ was stronger than that by PHQ, showing higher importance of PBQ than other OPP metabolites. Catalase and bathocuproine inhibited Cu(II)-mediated DNA damage by PBQ plus NADH and PHQ, suggesting that H2O2 reacts with Cu(I) to produce active species causing DNA damage. Electron spin resonance and UV-visible spectroscopic studies have demonstrated generation of semiquinone radical and superoxide from the reaction of PBQ with NADH or the Cu(II)-mediated autoxidation of PHQ. The present results suggest that these OPP metabolites cause oxidative DNA damage through H2O2 generation in cells, and the damage may lead to mutation and carcinogenesis. It is concluded that PBQ may play a more important role in the expression of OPP carcinogenicity than other OPP metabolites.

Inhibition of prostaglandin-H-synthase by o-phenylphenol and its metabolites.

Chronic administration of o-phenylphenol (OPP) is known to induce urinary bladder tumours in the Fischer rat. The underlying toxic mechanism is poorly understood. Recently, arachidonic acid (ARA)-dependent, prostaglandin-H-synthase (PHS)-catalysed metabolic activation of the OPP metabolite phenylhydroquinone (PHQ) to a genotoxic species was suggested to be involved in OPP toxicity. To investigate this hypothesis in more detail, we have studied the effects of OPP and its metabolites on PHS. When microsomal PHS from ovine seminal vesicles (OSV) was used as enzyme source, both OPP, PHQ, and 2-phenyl-1,4-benzoquinone (PBQ) inhibited PHS-cyclooxygenase. The inhibitory potency was inversely related to the ARA concentration in the assay; at 7 microM ARA IC50-values were: 13 microM (OPP), 17 microM (PHQ), and 190 microM (PBQ). In cells cultured from OSV, which express high PHS activity, 40 microM OPP almost completely suppressed prostaglandin formation. Studies with microsomal PHS demonstrated that PHQ was an excellent substrate for PHS-peroxidase; both ARA and hydrogen peroxide supported oxidation to PBQ. OPP was only a poor substrate for PHS, but inhibited the ARA-mediated and to a lesser extent also the hydrogen peroxide-mediated in vitro oxidation of PHQ. Moreover, PHQ at up to moderately cytotoxic concentrations (50 microM) did not induce micronuclei in OSV cell cultures. Taken together, our findings do not provide evidence for an ARA-dependent, PHS-catalysed formation of genotoxic species from PHQ. Moreover, it seems to be questionable whether such activation can effectively occur in vivo, since OPP and PHQ turned out to be efficient cyclooxygenase inhibitors, and high levels of OPP and PHQ were found at least in the urine of OPP-treated rats. On the other hand, inhibition of the formation of cytoprotective prostaglandins in the urogenital tract may play a crucial role in OPP-induced bladder carcinogenesis.

Effects of pH on nonenzymatic oxidation of phenylhydroquinone: potential role in urinary bladder carcinogenesis induced by o-phenylphenol in Fischer 344 rats.

o-Phenylphenol (OPP) and its sodium salt (SOPP) are broad spectrum fungicides and antibacterials to which humans are frequently exposed. Both OPP and SOPP have been found to cause cancer in the urinary bladder of male F344 rats at high doses, and the metabolite phenylhydroquinone (PHQ) is believed to play a key role in the carcinogenicity of these compounds. Tumor formation in the treated animals has also been shown to be significantly influenced by urinary pH. To provide additional insights into the mechanisms of OPP carcinogenesis, we have investigated the autoxidation of PHQ over the pH range commonly found in the urine of OPP- and SOPP-treated rats. Over the pH range studied (6.3-7.6), a curvilinear relationship between rate of PHQ oxidation and pH was observed. Phenylbenzoquinone (PBQ) was formed during the autoxidation of PHQ, with a formation yield of 0.92 +/- 0.02. In addition, the effects of PBQ and oxygen concentrations on PHQ autoxidation and the nonenzymatic conversion of PBQ to PHQ were also studied. Our data indicate that the production of reactive metabolites from PHQ involves a pH-independent (i.e., oxygen-dependent) and a pH-dependent pathway and that the rate of pH-dependent PHQ autoxidation was found to be enhanced by the presence of PBQ. A reaction mechanism has been formulated to explain the experimental data observed, with ionization of PHQ semiquinone being identified as a key step in reactive species production for the pH-dependent pathway. By combining data from OPP animal carcinogenicity studies with the proposed reaction pathway, a good correlation between the proposed formation of reactive species and bladder lesions was observed. These results indicate that the pH-dependent autoxidation of free PHQ metabolite in the urine may potentially be responsible for the tumorigenic effects of OPP and SOPP observed in the rat bladder.

Composites. 2. Reinforcement of Poly(ε-caprolactone) via Lyotropic Blends of Rigid-Rod Polyesters Derived from Substituted Terephthalic Acids

Two aryloxyterephthalic acids and two 2,5-bis(alkoxy)terephthalic acids were synthesized and polycondensed with hydroquinone (HQ), methylhydroquinone (MeHQ), phenylhydroquinone (PhHQ), or 4,4‘-dihydroxybiphenyl (DHBP). Eleven out of the possible 16 polyesters were selected for the preparation of blends with commercial poly(e-caprolactone), PCL, as the matrix. The properties of blends containing 1, 2, 4, or 8 wt % of the rigid-rod polymer were studied. The optical microscopy revealed birefringence for the entire blend below the melting temperature (Tm) of the rigid-rod polymer. The lyotropic character vanished and phase separation took place above the Tm of the rigid-rod polymer. The lyotropic blends (PCL acting as a solvent) showed a significant mechanical reinforcement effect, when examined by melt rheology and stress−strain measurements. This effect depended largely on the aromatic character of the substituents. The most surprising and important finding is the formation of lyotropic blends from a rigid-...

Thermotropic liquid-crystalline copolyesters containing substituted phenylene terephthalate and ethylene terephthalate units

Three series of aromatic, thermotropic copolyesters, based on terephthalic acid (TA), ethylene glycol (EG), and another diol were prepared. The third monomer was selected from three different hydroquinones including, ethoxyhydroquinone (EHQ), phenylhydroquinone (PHQ), and hydroquinone itself (HQ). The amounts of the different hydroquinone terephthalate units were varied while the amounts of ethylene terephthalate units remained constant. The copolymers and terpolymers were characterized for solubility, for morphology by polarized light microscopy (PLM), for molecular weight by solution viscometry, and by NMR, DSC, and TGA. At elevated temperatures all samples, when observed by PLM, displayed the characteristic texture of a nematic phase. The melting transition temperatures, Tm, were found to vary from 255 to 325°C, while the 5 wt % loss temperatures, Td, were found to vary from 330 to 440°C. The inherent viscosities varied from 0.6 to 1.9 dL/g. Increases in the HQ monomer content caused a decreased solubility and an increase in melting point. Copolymer compositions determined by NMR showed that only about one-half of the EG added was incorporated into the copolymers. © 1997 John Wiley & Sons, Inc.

Synthesis and Characterization of Thermotropic Aromatic Polyesters Derived from 3-Phenyl-4.4′-biphenyldicarboxylic Acid

A series of wholly aromatic polyesters were synthesized via bulk, melt polycondensation of 3-phenyl-4.4′-biphenyldicarboxylic acid (PBDA) and diacetates of aromatic diols such as hydroquinone (HQ), methylhydroquinone (MHQ), phenylhydroquinone (PHQ), 2-(α-phenylisopropyl) hydroquinone (PIHQ), 2,6-naphthalenediol (2,6-ND), 1,4-naphthalenediol (1,4-ND), and 4,4′-biphenol (BP). The polyesters were characterized for their crystallinity, thermal transition properties, and liquid crystallinity using wide-angle x-ray diffractometry (WAXD) and differential scanning calorimetry (DSC), and by observation of their optical textures under a polarizing microscope. It was found that all of the polyesters, with the only exception of the BP polyester, are amorphous. They showed optical textures characteristic of the nematic phase when heated above their glass transition (T g) or melting temperatures (T m). The T g values ranged from about 125° to 170°C depending on the structure of aromatic diol moieties.

Studies on thermotropic liquid crystalline polymers. XV. Synthesis and properties of liquid crystalline copoly(imide‐ester)s

Three series of the thermotropic liquid crystalline copoly(imide-ester)s were prepared by direct polycondensation. The first two series of the copoly(imide-ester)s were synthesized from N-(4-carboxyphenyl) trimellitimide with N,N-di(hydroxypropyl) pyromellitic diimide and various aromatic diols. The third series of copoly(imide-ester)s were prepared by N-(4-carboxyphenyl) trimellitimide with various imide-diols (methylene spacer = 2–6) and phenyl hydroquinone. The structures and thermal properties of the synthesized poly(imide-ester)s were examined by FTIR spectrum, wide-angle x-ray diffraction (WAXD), differential scanning calorimetry (DSC), thermal optical polarized microscope, and thermogravimetric analysis (TGA). The effects of the structures of the aromatic diols on the thermal properties of the resulting copoly(imide-ester)s were investigated. It was found that most of the copoly(imide-ester)s possessed excellent mesophase stabilities and thermostabilities. The mesophase stabilities of poly(imide-ester)s decreased with the increase of the size of lateral group, and the mesophase range increased with the increase of the amount of PhHQ. No significant odd-even effects were observed between the methylene spacer lengths and transition temperatures. © 1996 John Wiley & Sons, Inc.

Studies on thermotropic liquid crystalline polymers. XV. Synthesis and properties of liquid crystalline copoly(imide-ester)s

Three series of the thermotropic liquid crystalline copoly(imide-ester)s were prepared by direct polycondensation. The first two series of the copoly(imide-ester)s were synthesized from N-(4-carboxyphenyl) trimellitimide with N,N-di(hydroxypropyl) pyromellitic diimide and various aromatic diols. The third series of copoly(imide-ester)s were prepared by N-(4-carboxyphenyl) trimellitimide with various imide-diols (methylene spacer = 2–6) and phenyl hydroquinone. The structures and thermal properties of the synthesized poly(imide-ester)s were examined by FTIR spectrum, wide-angle x-ray diffraction (WAXD), differential scanning calorimetry (DSC), thermal optical polarized microscope, and thermogravimetric analysis (TGA). The effects of the structures of the aromatic diols on the thermal properties of the resulting copoly(imide-ester)s were investigated. It was found that most of the copoly(imide-ester)s possessed excellent mesophase stabilities and thermostabilities. The mesophase stabilities of poly(imide-ester)s decreased with the increase of the size of lateral group, and the mesophase range increased with the increase of the amount of PhHQ. No significant odd-even effects were observed between the methylene spacer lengths and transition temperatures. © 1996 John Wiley & Sons, Inc.

Synthesis and thermal transitions of a soluble, main chain, nematic liquid crystalline polymer exhibiting a kinetically trapped, disordered structure

An aromatic copolyester composed of 25 mol % phenyl hydroquinone, 10 mol % isophthalic acid, 40 mol % chloroterephthalic acid, and 25 mol % t-butyl hydroquinone (PICT) has been synthesized. This amorphous, glassy polymer is soluble in common organic solvents such as methylene chloride. Thin, solution-cast films may be prepared which are in a metastable, vitrified, optically isotropic state. On first heating of an isotropic film at 20°C/min in a calorimeter, one glass transition is observed at low temperature (approximately 49°C) and is ascribed to the glass/rubber transition of the metastable, isotropic polymer. This thermal event is followed by a small exotherm due to the development of order during the scan, which results in a second Tg at approximately 125°C. This Tg is associated with the glass/rubber transition of the ordered polymer. Nematic order can be developed by thermal annealing. The lower Tg increases toward the upper Tg as annealing time is increased. For an initially isotropic film annealed at 90°C, the increase of the lower Tg with annealing time and the increase in birefringence observed by optical microscopy are governed by similar kinetics. Isotropization occurs in the temperature range of 250–300°C. The nematic polymer is slightly more dense than its isotropic analog. No detectable differences between isotropic and nematic samples were observed in rotating frame proton spin lattice relaxation times. © 1996 John Wiley & Sons, Inc.

Synthesis and characterization of wholly aromatic polyesters derived from 1-phenyl-2,6-naphthalene-dicarboxylic acid and aromatic diols

A series of new wholly aromatic polyesters was synthesized by melt polycondensation of 1-phenyl-2,6-naphthalenedicarboxylic acid (PNDA) and diacetates of various aromatic diols. The aromatic diols studied are hydroquinone (HQ), methylhydroquinone (MHQ), phenylhydroquinone (PHQ), (α-phenylisopropyl)hydroquinone (PIHQ), 2,6-naphthalenediol (2,6-ND), 1,4-naphthalenediol (1,4-ND), and 4,4′-biphenol (BP). These polyesters were characterized for their crystallinity, glass transition temperature (Tg), melting temperature (Tm), liquid crystallinity, and thermal stability. In general, crystallinity of the polyesters are very low and the Tg values of the polyesters range from 150 to 172°C depending on the structure of aromatic diols. All of the polymers formed nematic phases above their Tm or Tg. The polyesters derived from PHQ and PIHQ are soluble in chlorinated hydrocarbon solvents. The initial decomposition temperatures of the polyesters are above 400°C under N2 atmosphere. © 1996 John Wiley & Sons, Inc.

Induction of 8-hydroxy-2'-deoxyguanosine in CHO-K1 cells exposed to phenyl-hydroquinone, a metabolite of ortho-phenylphenol.

The induction of 8-hydroxy-2'-deoxyguanosine (8-OHdG), an index of oxidative DNA modification, was investigated in CHO-K1 cells exposed to phenyl-hydroquinone (PHQ), a major metabolite of ortho-phenylphenol (OPP), an antimicrobial. Addition of PHQ at a concentration of 50 microM to CHO cell suspensions (10(6) cells/ml) induced slight elevation of intracellular 8-OHdG levels. Pretreatment of CHO cells with 3-amino-1,2,4-triazole (AT, 20 mM) enhanced PHQ-induced 8-OHdG formation which was accompanied by cell death. Pretreatment of CHO-K1 cells with AT (20 mM) and deferoxamine (DeFe, 20 mM) inhibited the formation of 8-OHdG as well as cell death caused by PHQ. Neither AT nor DeFe affected cell viability or the formation of 8-OHdG in untreated CHO cells during the incubation period. The loss of cellular glutathione induced by the addition of PHQ alone was enhanced by the pretreatment of CHO cells with AT or AT plus DeFe. When PHQ was added to AT-pretreated cell suspensions, the concentration of PHQ decreased with time. This decrease was accompanied by the formation of phenyl-benzoquinone (PBQ). These results suggest that the reactive oxygen species derived from autoxidation of PHQ which converts to PBQ via phenyl-semiquinone elicit DNA damage in CHO cells, especially when the activity of cellular catalase is inhibited.

Liquid crystalline aromatic polyesters formed with terephthalic acid, phenyl hydroquinone, and napthalene or anthracene diols

AbstractThe synthesis and characterization of aromatic copolyesters containing terephthalic acid and phenyl hydroquinone as the major constituents and either 1,4‐napthalene diol or 1,4‐anthracene diol as the minority comonomer is described. Both polymers melted in the vicinity of 300°C, giving birefringent fluids. Optical microscopy showed Schlieren textures consisting predominantly of inversion walls characteristic of the nematic phase. The clearing temperature was in the vicinity of 460°C, but was accompanied by charring. DSC experiments showed a high glass transition temperature of 130–160°C for both polymers. Crystalnematic and nematic‐isotropic endotherms were observed on heating; however, degradation took place near the isotropization temperature. Thus, on cooling, the sequence was reversible only if the previous heating was beyond the crystal‐nematic but below the isotropization temperature. The polymers were stable in terms of gross weight loss until about 450°C, though there were indications that crosslinking occurred above about 400°C over a short period of time. The polymers formed low‐viscosity injection‐molding compounds, but to use them effectively, it would require mold‐gate designs that reduce the “jetting” tendency for liquid crystal polymer melts, which result in weld lines. © 1995 John Wiley &amp; Sons, Inc.

Thermotropic copolyesters from phenylhydroquinone, hydroquinone, 4,4'-diphenyldicarboxylic acid and p-hydroxybenzoic acid

Copolyesters from phenylhydroquinone (Ph-HQ), hydroquinone (HQ), 4.4'diphenyldicarboxylic acid (BB) and p-hydroxybenzoic acid (HBA) were prepared and their thermal and mechanical properties were investigated. As-spun fibres and injection moulded specimens from Ph-HQ/BB,'HBA exhibited low moduli. whereas those from Ph-HQHQ/BB/HBA exhibited high moduli probably due to the high packing density of the polymer chain caused by incorporation of HQ structural unLts. Although the modulus of as-spun fibres from Ph-HQ'BBHBA did not correlate with the number of HBA units, the modulus of injection moulded specimens decreased with increase in the number of HBA units. It is most likely that rigidity of the polymer chain was reduced by incorporation of HBA units. Thus, packing density and rigidity of the polymer chain seem to be influential factors in determining the modulus of injection moulded specimens.