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PubMed1993

Hydroxylation of salicylate by the in vitro diaphragm: evidence for hydroxyl radical production during fatigue.

There is increasing evidence that oxygen-derived free radicals produced during strenuous work by the diaphragm may contribute to diaphragm fatigue and/or injury. However, the precise identity of these oxygen radicals remains unknown, inasmuch as oxygen free radicals are extremely short lived and their detection in biologic systems is quite difficult. There is recent evidence that the salicylate-trapping method may be a useful means of monitoring tissue production of hydroxyl radical (.OH). This method is predicated on the fact that salicylate's phenolic ring can be attacked by .OH at the 3 or 5 position to yield 2,3- or 2,5-dihydroxybenzoic acid (DHB). These metabolites are stable and can be identified by high-performance liquid chromatography (HPLC) coupled with electrochemical or ultraviolet detection. To test the hypothesis that hydroxylated salicylates are produced during diaphragm fatigue, we exposed in vitro rat diaphragm strips to a physiological saline solution containing 2.0 mM sodium salicylate for approximately 15 min. The solution was then removed, and the strips were fatigued (20 Hz, 200-ms train duration, 1 train/s) via phrenic nerve stimulation for 30 s-10 min. The diaphragm strips were subsequently homogenized, and the homogenate was analyzed by HPLC coupled with ultraviolet detection. Levels of 2,3-DHB were significantly higher in fatigued than in control nonfatigued strips. There was also a significant correlation between the amount of 2,3-DHB in the fatigued muscle and the accumulated tension-time product developed during fatigue. 2,5-DHB was not consistently identified in control or experimental strips.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed2000

Effects of trans-resveratrol on copper-dependent hydroxyl-radical formation and DNA damage: evidence for hydroxyl-radical scavenging and a novel, glutathione-sparing mechanism of action.

Resveratrol (3,5,4'-trihydroxy-trans-stilbene) is a natural product occurring in grapes and various other plants with medicinal properties. The phenolic antioxidant has been identified as a potential cancer chemopreventative agent and its presence in red wine has been suggested to be linked to the low incidence of heart disease in some regions of France. Recently, however, resveratrol was reported to promote DNA fragmentation in the presence of copper ions (K. Fukuhara and N. Miyata, 1998, Bioorg. Med. Chem. Lett. 8, 3187-3192), prompting us to investigate this phenomenon in mechanistic detail. By acting as a reducing agent, resveratrol was found to promote hydroxyl-radical (*OH) formation by DNA-bound Cu(H) ions. However, in the presence of either ascorbic acid or glutathione (i.e., under more physiological conditions), the phenolic lost this property and behaved as an antioxidant. In the ascorbate system, resveratrol had no effect on the rate of *OH formation, but protected DNA from damage by acting as a radical-scavenging antioxidant. In contrast, in the glutathione system, resveratrol inhibited *OH formation via a novel mechanism involving the inhibition of glutathione disulfide formation. We have concluded, therefore, that the DNA-damaging properties of resveratrol, identified recently by Fukuhara and Miyata, will be of no significance under physiological conditions. To the contrary, we have demonstrated that the phenolic behaves as a powerful antioxidant, both via classical, hydroxyl-radical scavenging and via a novel, glutathione-sparing mechanism.

Antioxidants↗
PubMed1985

Investigation of rat liver microsomal 6 beta-hydroxylation of 4-androstene-3,17-dione and 4-pregnene-3,20-dione using methodology which excludes steroid-3-imine induced introduction of the 6 beta-hydroxyl group.

To avoid artefactual 6 beta-hydroxylation of 3-oxo-4-ene steroids due to steroid-3-imine formation and rearrangement a combined extraction and liquid chromatography purification procedure for incubated rat liver microsomes has been worked out. With this procedure no nonenzymatic 6 beta-hydroxylation could be observed. Conventional termination of incubations with male rat liver microsomes (105,000 g sediments) and 4-14 C-labelled 4-androstene-3,17-dione (or progesterone) by solvent extraction and evaporation might lead to a 30% overestimation of the formation of 6 beta-hydroxy-derivatives at substrate saturation. Furthermore this work-up procedure produces 6-oxo-derivatives which were not observed when the new procedure was used. By elimination of the artefactual 6-oxygenation some properties of the male rat liver microsomal 4-androstene-3,17-dione 6 beta-hydroxylase have been studied, and the activity has been compared to the artefact produced by solvent extraction and evaporation. Using the combined extraction-liquid chromatography purification it was demonstrated that the microsomal 6 beta-hydroxylase active on 4-androstene-3,17-dione and progesterone was inhibited to 95% by carbon monoxide. This makes previous suggestions regarding participation of a non cytochrome P450-dependent 4-androstene-3,17-dione 6 beta-hydroxylase less likely.

Androstenedione↗
PubMed2002

Differential interactions of estrogens and antiestrogens at the 17 beta-hydroxyl or counterpart hydroxyl with histidine 524 of the human estrogen receptor alpha.

We investigated the role of H524 of the human estrogen receptor alpha (ERalpha) for the binding of various estrogens [estradiol (E(2)), 3-deoxyestradiol (3-dE(2)), and 17beta-deoxyestradiol (17beta-dE(2))] and antiestrogens [4-hydroxytamoxifen (OHT), RU 39 411 (RU), and raloxifene (Ral)], which possess the 17beta-hydroxyl or counterpart hydroxyl (designated: 17beta/c-OH), with the exception of 17beta-dE(2) and OHT. The work involved a comparison of the binding affinities of these ligands for wild-type and H524 mutant ERs, modified or not with diethyl pyrocarbonate (DEPC), a selective histidine reagent. Alanine substitution of H524 did not significantly change the association affinity constant (relative to OHT) of 17beta-dE(2), whereas those of RU, Ral, E(2), and 3-dE(2) were decreased 3-fold, 14-fold, 24-fold, and 49-fold, respectively. Values of the two ligands available in radiolabeled form (E(2) and OHT) were correlated with the dissociation rate constants, which were increased 250-fold and 2-fold, respectively. The action of DEPC on wild-type ER led to a homogeneous ER population which still bound antiestrogens and 17beta-dE(2) with practically unchanged affinities (less than 4-fold decreases in relative affinity constants), while E(2) and 3-dE(2) displayed markedly decreased affinities (56-fold decrease for E(2)). Conversely, DEPC treatment of H524A mutant ER did not induce marked decreases in the relative affinities of any of the checked compounds (decreases </=3-fold). All of these effects appeared to involve H524 as the H516A mutant behaved as wild-type ER. These combined data relative to mutated or DEPC-modified ER converged to support that the interaction of 17beta/c-OH of ER ligands with H524 is strong for estrogens and weaker for antiestrogens, with quantitative or qualitative differences between the binding modes of the latter, as illustrated by RU and Ral. The abilities of E(2) and OHT to protect the various ER types against inactivation by DEPC were strikingly different: OHT totally prevented the effect of DEPC on wild-type, H516A, and H524A ERs, while E(2) only partially protected wild-type and H516A ERs (H516A ER > wild-type ER) and very weakly protected H524A ER. Molecular modeling was tentatively used to interpret the biochemical results.

Alanine↗
PubMed2001

Rapid and specific detection of hydroxyl radical using an ultraweak chemiluminescence analyzer and a low-level chemiluminescence emitter: application to hydroxyl radical-scavenging ability of aqueous extracts of Food constituents.

With the availability of an ultraweak chemiluminescence analyzer, it is possible to monitor the production of a specific oxygen-derived reactive species, such as hydroxyl radical ((*)OH), whenever a suitable chemiluminescent probe is obtainable. Reported herein is the development of a rapid and specific method for detecting (*)OH production using a specific probe, indoxyl-beta-glucuronide (IBG), a low-level chemiluminescence emitter. Using the Fenton reagent as a source of (*)OH, it was shown that IBG could elicit a very strong intensity of chemiluminescence (CL) (16200 +/- 200 photon counts/s). Conversely, IBG was shown to be insensitive to either superoxide radical or hydrogen peroxide with their CL intensities nearly close to the background values (25 +/- 5 and 180 +/- 20 photon counts/s, respectively). Furthermore, it was also shown that this IBG-based CL production could be effectively quenched by the addition of (*)OH scavengers such as sodium salicylate, dimethyl sulfoxide, and penicillamine to the assay system. Taken together, these data indicate that IBG is a specific CL probe suitable for monitoring the production of (*)OH. This system demonstrated inhibitory activities of various aqueous extracts of food constituents on the CL of hydroxyl radicals generated by Fenton's reagents with the order of scavenging efficiencies being Prunus mume > Cordyceps sinensin > Lilium lancifolium > Astragalus membranceus.

Free Radical Scavengers↗
PubMed2002

Transformation of barbituric acid into alloxan by hydroxyl radicals: interaction with melatonin and with other hydroxyl radical scavengers.

Barbituric acid (2,4,6-pyrimidinetrione) can be transformed by a non-enzymatic hydroxylation into alloxan (2,4,5,6-pyrimidinetetrone). This transformation can be used as a reaction indicating the formation of hydroxyl radicals (.OH). This conversion was detected using HPLC. Formation of .OH was demonstrated by electron spin resonance (ESR) spectroscopy combined with spin-trapping techniques. It was shown that .OH generated via the Fenton reaction abstracts first a hydrogen atom from barbituric acid (BA) and forms intermediately a paramagnetic derivative of BA. After a second attack by another .OH, the BA radical is transformed into dialuric acid (DA), which autoxidizes via the alloxan radical (.ALX) to ALX. Superoxide radicals (.O2-) are formed during autoxidation of DA and.ALX. They are able to regenerate ferrous ions. As a result, traces of iron salts are capable of catalyzing the conversion of large amounts of BA into ALX. Several scavengers of .OH were tested with regard to their efficiency in preventing the transformation of BA into ALX. Of all the scavengers analyzed, melatonin was shown to be one of the most potent compounds.

Alloxan↗
PubMed1985

Stereoselective mephobarbital hydroxylation cosegregates with mephenytoin hydroxylation.

The 8-hour urinary recovery of 4-hydroxy-mephobarbital has been measured after oral administration of racemic mephobarbital (90 mg) in 17 extensive (EM) and six poor (PM) metabolizer phenotypes of mephenytoin. The recovery of this metabolite was measurable in every EM and ranged from 2.5% to 48% (10.9% +/- 1.9% of dose), but was not detected in any PM (less than 1% of dose). In EMs, the 8-hour urine recovery of 4-OH-mephobarbital after mephobarbital was approximately half that of 4-OH-mephenytoin over the same time after mephenytoin administration. One EM received similar doses of R- and S-mephobarbital on separate occasions. Urinary recovery of 4-OH-mephobarbital was 33% and less than 1%, respectively. These results suggest that mephobarbital is stereoselectively hydroxylated by the same drug metabolizing enzyme that is responsible for the stereoselective aromatic hydroxylation of mephenytoin.

Administration, Oral↗
PubMed1990

A cDNA encoding a rat mitochondrial cytochrome P450 catalyzing both the 26-hydroxylation of cholesterol and 25-hydroxylation of vitamin D3: gonadotropic regulation of the cognate mRNA in ovaries.

A cDNA expression library prepared from rat liver RNA was screened with a polyclonal antibody specific for mitochondrial vitamin D3 25-hydroxylase and a cDNA for rabbit liver mitochondrial cytochrome P450c26 (CYP 26), yielding cDNA clones with identical sequences. The deduced amino acid sequence derived from a 1.9-kb full-length cDNA was 73% identical to that of rabbit cytochrome P450c26. A monoclonal antibody was used to demonstrate that the product of the 1.9-kb cDNA clone was targeted to the mitochondrial compartment when expressed in COS cells. Mitochondrial membranes containing the expressed protein showed both vitamin D3 25-hydroxylase and cholesterol 26-hydroxylase activities when reconstituted with ferredoxin reductase and ferredoxin, demonstrating that the same P450, designated as P450c26/25, can catalyze both reactions. Northern blot analysis revealed that the P450c26/25 cDNA hybridizes with a 2.4-kb RNA from rat liver and unstimulated ovaries. Treatment of rats with pregnant mare's serum gonadotropin resulted in a fivefold increase in the 2.4-kb mRNA as well as the appearance of a 2.1-kb mRNA species in the ovaries. Our findings document the presence of a regulated bifunctional mitochondrial cytochrome P450 capable of catalyzing the 25-hydroxylation of vitamin D3 and the 26-hydroxylation of cholesterol.

Amino Acid Sequence↗
PubMed1994

Reaction mechanism underlying CMP-N-acetylneuraminic acid hydroxylation in mouse liver: formation of a ternary complex of cytochrome b5, CMP-N-acetylneuraminic acid, and a hydroxylation enzyme.

We have proposed that CMP-N-acetylneuraminic acid (CMP-NeuAc) hydroxylation is mediated by an electron transport system consisting of cytochrome b5 (b5), b5 reducing factor(s), and CMP-NeuAc hydroxylase, all of which have been detected in the cytosolic fraction of mouse liver [Kozutsumi, Y., Kawano, T., Yamakawa, T., & Suzuki, A. (1990) J. Biochem. 108, 704-706]. In order to elucidate the reaction mechanism underlying CMP-NeuAc hydroxylation, the interaction between b5 and the hydroxylase was studied using a b5-immobilized affinity column. The enzyme activity was retarded on the b5 column in the presence of the substrate, CMP-NeuAc, but not in the presence of the reaction product, CMP-N-glycolyneuraminic acid (CMP-NeuGc). These findings suggest that the binding of CMP-NeuAc to CMP-NeuAc hydroxylase changes the conformation of the enzyme so as to construct a recognition site for b5, followed by the formation of a ternary complex through this domain. Then the transport of electrons from NAD(P)H to the enzyme through b5 takes place, CMP-NeuAc is converted to CMP-NeuGc, and finally the ternary complex dissociates into its components to release CMP-NeuGc. It is known that a soluble form of b5 is abundant in erythrocytes and is synthesized from a mRNA different from that for the microsomal form of b5. In order to determine the origin of b5 detected in the cytosolic fraction of mouse liver, the molecular forms of b5 mRNA expressed in mouse liver were analyzed.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed2001

P-hydroxylation of phenobarbital: relationship to (S)-mephenytoin hydroxylation (CYP2C19) polymorphism.

The aim of the current study was to compare the pharmacokinetics of phenobarbital (PB) in extensive metabolizers (EMs) and poor metabolizers (PMs) of S-mephenytoin. Ten healthy volunteers (5 EMs and 5 PMs) were given 30 mg PB daily for 14 days. PB and p-hydroxyphenobarbital (p-OHPB) in serum and urine were measured by high-performance liquid chromatography (HPLC). Urinary excretion (12.5% versus 7.7%) and formation clearance (29.8 versus 21.1 mL/h) of p-OHPB, one of the main metabolites of PB, were significantly lower (p < .05) in PMs than in EMs. However, area under the serum concentration-time curve (153.3 in the EMs versus 122.9 microg x h/mL in the PMs), total (210.8 versus 254.9 mL/h) and renal clearance (53.1 versus 66.1 mL/h) of PB were identical between the two groups. To compare the inducibility of CYP2C19, mephenytoin was also given prior to and on the last day of PB treatment. The urinary level of 4'-hydroxymephenytoin was analyzed by a validated gas chromatograpy/mass spectrometry (GC/MS) method. The mephenytoin hydroxylation index did not change in either EMs (1.42 versus 1.42) or PMs (341.4 versus 403.5), showing that CYP2C19 was not induced by treatment with PB. These results indicated that the p-hydroxylation pathway of PB co-segregates with the CYP2C19 metabolic polymorphism. However, the overall disposition kinetics of PB were not different between EMs and PMs, and therefore polymorphic CYP2C19 seems have no major clinical implications.

Adult↗
PubMed1988

Formation of hydroxyl radicals in biological systems. Does myoglobin stimulate hydroxyl radical formation from hydrogen peroxide?

Incubation of horse-heart oxymyoglobin or metmyoglobin with excess H2O2 causes formation of myoglobin(IV), followed by haem degradation. At the time when haem degradation is observed, hydroxyl radicals (.OH) can be detected in the reaction mixture by their ability to degrade the sugar deoxyribose. Detection of hydroxyl radicals can be decreased by transferrin or by .OH scavengers (mannitol, arginine, phenylalanine) but not by urea. Neither transferrin nor any of these scavengers inhibit the haem degradation. It is concluded that intact oxymyoglobin or metmyoglobin molecules do not react with H2O2 to form .OH detectable by deoxyribose, but that H2O2 eventually leads to release of iron ions from the proteins. These released iron ions can react to form .OH outside the protein or close to its surface. Salicylate and the iron chelator desferrioxamine stabilize myoglobin and prevent haem degradation. The biological importance of .OH generated using iron ions released from myoglobin by H2O2 is discussed in relation to myocardial reoxygenation injury.

Animals↗
PubMed1990

Clofibrate-inducible rat hepatic P450s IVA1 and IVA3 catalyze the omega- and (omega-1)-hydroxylation of fatty acids and the omega-hydroxylation of prostaglandins E1 and F2 alpha.

Cytochromes P450IVA1 and IVA3 display 72% amino acid sequence similarity and are expressed in livers of rats treated with the hypolipidemic drug clofibrate. The catalytic activities of IVA1 and IVA3 were examined by cDNA-directed expression using vaccinia virus. cDNA-expressed IVA1 and IVA3 had relative Mrs of 51,500 and 52,000, respectively, on SDS-polyacrylamide gels. Both enzymes displayed reduced, CO-bound absorption spectra with lambda max of 452.5 nm. IVA1 and IVA3 hydroxylated lauric acid at the omega and omega-1 positions with equivalent omega/omega-1 ratios of about 12.5. IVA1 had a substrate turnover of 21 min-1 which was about fourfold higher than that of IVA3. The omega and omega-1 hydroxylation of palmitic acid was also catalyzed by these P450s with combined turnover numbers for both metabolites of 45 min-1 or 18 min-1 for IVA1 and IVA3, respectively. The omega/omega-1 oxidation ratio of IVA1 for palmitate was 1.25 which was almost fourfold higher than that obtained for IVA3. These enzymes also catalyzed omega oxidation of the physiologically important eicosanoids prostaglandins E1 and F2 alpha with turnover numbers of about one-tenth those calculated for fatty acid oxidations. No omega-1 hydroxy metabolites were produced. These studies indicate that the P450 enzymes IVA1 and IVA3 are able to catalyze the oxidations of both fatty acids and prostaglandins.

Alprostadil↗
PubMed2004

A new proposal for the mechanism of glycine hydroxylation as catalyzed by peptidylglycine alpha-hydroxylating monooxygenase (PHM).

The title enzyme, peptidylglycine alpha-hydroxylating monooxygenase (PHM), is essential to the in vivo generation of a wide variety of physiologically significant alpha-amidated peptide hormones from the corresponding C-terminal glycine-extended prohormones. Over a 20-year period of time a massive amount of experimental information about the enzyme has accumulated, but its mechanism of action has remained obscure. A major stumbling block to proposed mechanisms is the fact that the two copper atoms found in the active site are fixed 11 A apart. A novel mechanism is now proposed which accommodates and, indeed, requires this separation and proceeds through energetically accessible steps. It is proposed that hydroxylation at the terminal glycine residue of the C-terminal glycine-extended prohormone proceeds first by a concerted sequence of single-electron electromeric shifts, whereby both copper atoms are oxidized to Cu(II), oxygen is reduced to peroxide coordinated to Cu(M), and the glycyl group is tautomerized to its enolate coordinately bound to Cu(H). Upon subsequent reversion to the carbonyl tautomer, by a sequence of two-electron shifts, the enolate as nucleophile reacts with peroxide as electrophile, generating product alpha-hydroxyglycine, decoordinated from Cu(H), reopening the mouth of the active-site pocket to egress of product and ingress of substrates.

Animals↗
PubMed1977

Use of silylating agents for the identification of hydroxylated steroids by gas chromatography and gas chromatography-mass spectrometry. Discrimination between phenolic and alcoholic hydroxyl groups.

A phenolic trimethylsilyl (TMS) group was selectively exchanged for a dimethylalkylsilyl (DMAS) group on a gas chromatographic column by use of sandwich injection technique with DMAS-imidazole, and a TMS ether derivative of a phenolic steroid was converted into a DMAS ether or a mixed TMS and DMAS ether derivative with over 95% recovery. The selective exchange reaction seemed to be caused by the difference in lability between the ethereal TMS linkages to phenolic and alcoholic hydroxyl groups. This selectivity was found to be useful for discriminating gas chromatographically between the phenolic and alcoholic hydroxyl groups in steroids.

Alcohols↗
PubMed1985

Inhibition of the mutagenicity of bay-region diol-epoxides of polycyclic aromatic hydrocarbons by tannic acid, hydroxylated anthraquinones and hydroxylated cinnamic acid derivatives.

Tannic acid and several hydroxylated anthraquinone and cinnamic acid derivatives inhibited the mutagenic activity of (+/-)-7 beta,8 alpha-dihydroxy-9 alpha,10 alpha-epoxy-7,8,9,10-tetrahydrobenzo [a]pyrene (B[a]P 7,8-diol-9,10-epoxide-2), an ultimate mutagenic and carcinogenic metabolite of benzo [a]pyrene. The mutagenic activity of 0.05 nmol of B[a]P 7,8-diol-9,10-epoxide-2 towards strain TA 100 of Salmonella typhimurium was inhibited 50% by incubation of the bacteria and the diol-epoxide with tannic acid (0.5 nmol), anthraflavic acid (7 nmol), rufigallol (7 nmol), quinalizarin (10 nmol), alizarin (30 nmol), purpurin (60 nmol), and danthron (88 nmol). Dose-dependent, but weaker antimutagenic activity was observed for quinizarin, and a number of hydroxylated cinamic acid derivatives. Gallic acid and m-digallic acid, major components of tannic acid, possessed less than 1% of the anti-mutagenic activity of tannic acid, although m-digallic acid was over 3 times more active than gallic acid. The anti-mutagenic activity of tannic acid was a result of its interaction with B[a]P 7,8-diol-9,10-epoxide-2 since the rate of disappearance of the diol-epoxide from cell-free solutions in 1:9dioxane:water was markedly stimulated by the polyphenol. Tannic acid was a highly potent inhibitor of the mutagenic activity of the bay-region diol-epoxides of benzo[a]pyrene, dibenzo[a,h]pyrene and dibenzo[a,i]pyrene, but higher concentrations of tannic acid were needed to inhibit the mutagenicity of the chemically less reactive benzo[a]-pyrene 4,5-oxide and the bay-region diol-epoxides of benz[a]-anthracene, chrysene and benz[c]phenanthrene.

7,8-Dihydro-7,8-dihydroxybenzo(a)pyrene 9,10-oxide↗
PubMed2006

[The measurement of the ratio of primary hydroxyl group to second hydroxyl group in polyether polyol by near infrared spectrum].

The method of near infrared spectrum, combined with derivative spectrum and multiple linear regression was applied to measure the ratio of primary hydroxyl group to second hydroxyl group in polyether polyol. The authors obtained good predictive results by using the method in this experiment. The work is very helpful for the on-line measurement of polyether polyol.

English Abstract↗
PubMed1988

Aromatic hydroxylation of phenylalanine as an assay for hydroxyl radicals: application to activated human neutrophils and to the heme protein leghemoglobin.

Attack of hydroxyl radical (.OH), generated by a Fenton system at physiological pH, upon L-phenylalanine produces three isomeric tyrosines, o-tyrosine (2-hydroxyphenylalanine), m-tyrosine (3-hydroxyphenylalanine), and p-tyrosine (4-hydroxyphenylalanine). These may be separated by high-performance liquid chromatography and measured using an electrochemical detector. Since L-phenylalanine is relatively nontoxic, it is proposed that generation of these three tyrosines from phenylalanine can be used as an assay for .OH in biological systems. The use of the assay to measure .OH production by leghemoglobin (plus H2O2) and by activated human neutrophils is described. No .OH production by activated human neutrophils was observed unless a source of iron ions was added to the reaction mixture, which suggests that these cells do not release an iron "promoter" of .OH generation from superoxide and hydrogen peroxide.

Chromatography, High Pressure Liquid↗
PubMed2001

High-performance liquid chromatographic assay of hydroxyl free radical using salicylic acid hydroxylation during in vitro experiments involving thiols.

A HPLC method was developed to monitor the production of hydroxyl free radical (*OH) produced during in vitro experiments: (i) a chemical reaction involving EDTA chelated ferric ion and various exogenous and endogenous thiols [glutathione (GSH) and its metabolites], and (ii) an enzymatic reaction corresponding to the breakdown of GSH catalyzed by gamma-glutamyltransferase (GGT). The method relies upon the use of a selective trapping reagent of *OH: salicylic acid (SA). The three resulting dihydroxylated products, i.e., 2,3-dihydroxybenzoic acid (DHB), 2,5-DHB and catechol, were measured in an ion-pairing reversed-phase HPLC system coupled with amperometric detection; the sum of the three concentrations was used to quantify the production of *OH during in vitro experiments. Resulting data demonstrate that *OH is produced during Fenton-like reactions involving thiols and GSH catabolism via GGT.

3T3 Cells↗