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PubMed2003

Protective effect of ketoconazole against experimentally induced gastric ulcers in rats.

Recent studies suggest the critical role of inflammatory mediators in the genesis and healing of gastric ulcers. Ketoconazole a commonly used anti-fungal agent has a potent immunomodulatory action. The present investigation was undertaken to study the effect of ketoconazole on chemically and stress induced gastric ulcers in rats. Experimental gastric lesions in rats were induced by water immersion restraint stress, indomethacin and ethanol. Acid secretion studies were undertaken in pylorus ligated rats with and without ketoconazole. The level of myeloperoxidase (marker of neutrophil activity) non-protein sulfhydryl compounds and gastric wall mucus were measured after ethanol induced gastric lesions. Ketoconazole treatment resulted in significant protection against stress; indomethacin and ethanol induced gastric lesions in rats. Ketoconazole also dose dependently attenuated ethanol induced increase in myeloperoxidase activity and protected gastric mucosa against ethanol-induced depletion of non-protein sulfhydryl. These findings point towards the mediation of neutrophils and sulfhydryl compounds in ketoconazole induced cytoprotection. In conclusion, this study clearly shows anti-acid secretory, anti-ulcer and cytoprotective activity of ketoconazole.

Animals↗
PubMed1993

Some properties of lysosomal arylamidase in rat liver.

Lysosomal arylamidase in rat liver was reassessed. The arylamidase was distinguishable into seven types having different isoelectric points by isoelectric fractionation. All the types hydrolyzed valine beta-naphthylamide most rapidly among amino acid beta-naphthylamides tested, but did not hydrolyze arginine beta-naphthylamide. These enzymes exhibited maximum activities at pH 7.0. They had a molecular weight of 135,000 by gel filtration on a Sephacryl S-200. They were all inhibited by sulfhydryl-blocking reagents and activated by sulfhydryl compounds, indicating to be cysteine proteases.

Aminopeptidases↗
PubMed1975

Purification and characterization of extracellular proteinases of Aspergillus oryzae.

The extracellular proteinases of Aspergillus oryzae EI 212 were separated into two active fractions by (NH4)2SO4 and ethanol fractionation followed by diethylaminoethyl-Sephadex A-50 and hydroxyapatite chromatography. The molecular weight was estimated by gel filtration to be about 70,000 and 35,000 for proteinases I and II, respectively. Optimum pH for casein and hemoglobin hydrolysis was 6.5 at 60 C for proteinase I and 10.0 at 45 C for proteinase II, and for gelatin hydrolysis it was 6.5 at 45 C for both enzymes. The enzymes were stable over the pH range 6 to 8 at 30 C for 60 min. The enzyme activity for both the proteinases was accelerated by Cu2+ and inhibited by Fe2+, Fe3+, Hg2+, and Ag+. Halogenators (e.g., N-chlorosuccinimide) and diisopropyl fluorophosphate inhibited proteinase II. Sulfhydryl reagents such as p-chloromercuribenzoate and iodoacetate inhibited proteinase I. Sulfhydryl compounds accelerated the action of both enzymes.

Ammonium Sulfate↗
PubMed1978

The mercuric and organomercurial detoxifying enzymes from a plasmid-bearing strain of Escherichia coli.

Two separate enzymes, which determine resistance to inorganic mercury and organomercurials, have been purified from the plasmid-bearing Escherichia coli strain J53-1(R831). The mercuric reductase that reduces Hg2+ to volatile Hg0 was purified about 240-fold from the 160,000 X g supernatant of French press disrupted cells. This enzyme contains bound FAD, requires NADPH as an electron donor, and requires the presence of a sulfhydryl compound for activity. The reductase has a Km of 13 micron HgCl2, a pH optimum of 7.5 in 50 mM sodium phosphate buffer, an isoelectric point of 5.3, a Stokes radius of 50 A, and a molecular weight of about 180,000. The subunit molecular weight, determined by gel electrophoresis in the presence of sodium dodecyl sulfate, is about 63,000 +/- 2,000. These results suggest that the native enzyme is composed of three identical subunits. The organomercurial hydrolase, which breaks the mercury-carbon bond in compounds such as methylmercuric chloride, phenylmercuric acetate, and ethylmercuric chloride, was purified about 38-fold over the starting material. This enzyme has a Km of 0.56 micron for ethylmercuric chloride, a Km of 7.7 micron for methylmercuric chloride, and two Km values of 0.24 micron and over 200 micron for phenylmercuric acetate. The hydrolase has an isoelectric point of 5.5, requires the presence of EDTA and a sulfhydryl compound for activity, has a Stokes radius of 24 A, and has a molecular weight of about 43,000 +/- 4,000.

Drug Resistance, Microbial↗
PubMed1995

Selective protection against IgG binding to red cells treated with phthalocyanines and red light for virus inactivation.

BACKGROUND: Irradiation with red light of red cells (RBCs) containing the photodynamically active phthalocyanine (Pc) dyes is being studied for inactivation of lipid-enveloped viruses. One of the outstanding problems with this treatment is the binding of IgG to RBCs. The effects of oxygen and type I or type II quenchers on this IgG uptake were evaluated. STUDY DESIGN AND METHODS: The Pc compounds used were aluminum phthalocyanine tetrasulfonate (AIPcS4), HOSiPcOSi(CH3)2(CH2)3N(CH3)2 (Pc 4); HOSiPcOSi(CH3)2(CH2)3N+(CH3)3I- (Pc 5); and SiPcOSi[(CH3)2(CH2)3N+(CH3)3](2)2I- (Pc 6). RBCs were analyzed by flow cytometry for the presence of IgG. RESULTS: Irradiation with red light for 30 minutes of RBCs containing either 2 microM Pc 4, 2 microM Pc 5, 2 microM Pc 6, or 6.5 microM AIPcS4 resulted in an uptake of IgG. These conditions completely inactivated the lipid-enveloped vesicular stomatitis virus (VSV) (> 5 log10 kill). IgG uptake was reduced when oxygen was depleted. The addition of reduced glutathione (GSH) or mercaptoethanol prevented the binding of IgG with RBCs treated with AIPcS4, Pc 4, Pc 5, and Pc 6. Specific binding of IgG2 but not of C3d was observed upon irradiation of RBCs with Pc 5 and Pc 6 in the absence of GSH. No gross changes were observed in RBC antigen strength after irradiation with the dyes in the presence of GSH. Inactivation of VSV by Pc plus light was not affected by GSH. CONCLUSION: Sulfhydryl compounds are useful in preventing IgG binding to RBCs following Pc photosensitization. Since virus inactivation proceeds at the same rate in the presence and the absence of sulfhydryl compounds, their addition to treated RBCs should allow crossmatching for transfusion after treatment. The binding of IgG depends to a large extent on the generation of reactive oxygen species.

Antiviral Agents↗
PubMed1997

2-Methyl-thiazolidine-2,4-dicarboxylic acid as prodrug of L-cysteine. Protection against paracetamol hepatotoxicity in mice.

Toxic doses of paracetamol (acetaminophen) destroy the cellular defense system in hepatic tissue. The degree of the destruction can be assessed be measuring the metabolism of sulfhydryl compounds, oxygen radicals and the release of certain enzymes. Administration of 2-methyl-thiazolidine-2,4-dicarboxylic acid (CP; 1.2 mmol/kg) to mice 12 h prior to a toxic dose of paracetamol (600 mg/kg) suppressed the increase of aminotransferase activities in blood serum and the levels of reactive oxygen species in liver tissue. A protective effect of CP was also observed with respect to depletion of non-protein sulfhydryl compounds, cysteine and glycogen. The findings demonstrate that the cysteine prodrug CP is effective in preventing liver damage of a hepatotoxic dose of paracetamol in vivo. A further advantage of the new compound is the long duration of the effect of more than 12 h.

Acetaminophen↗
PubMed2004

NADPH dependent activation of microsomal glutathione transferase 1.

Microsomal glutathione transferase 1 (MGST1) can become activated up to 30-fold by several mechanisms in vitro (e.g. covalent modification by reactive electrophiles such as N-ethylmaleimide (NEM)). Activation has also been observed in vivo during oxidative stress. It has been noted that an NADPH generating system (g.s.) can activate MGST1 (up to 2-fold) in microsomal incubations, but the mechanism was unclear. We show here that NADPH g.s treatment impaired N-ethylmaleimide activation, indicating a shared target (identified as cysteine-49 in the latter case). Furthermore, NADPH activation was prevented by sulfhydryl compounds (glutathione and dithiothreitol). A well established candidate for activation would be oxidative stress, however we could exclude that oxidation mediated by cytochrome P450 2E1 (or flavine monooxygenase) was responsible for activation under a defined set of experimental conditions since superoxide or hydrogen peroxide alone did not activate the enzyme (in microsomes prepared by our routine procedure). Actually, the ability of MGST1 to become activated by hydrogen peroxide is critically dependent on the microsome preparation method (which influences hydrogen peroxide decomposition rate as shown here), explaining variable results in the literature. NADPH g.s. dependent activation of MGST1 could instead be explained, at least partly, by a direct effect observed also with purified enzyme (up to 1.4-fold activation). This activation was inhibited by sulfhydryl compounds and thus displays the same characteristics as that of the microsomal system. Whereas NADPH, and also ATP, activated purified MGST1, several nucleotide analogues did not, demonstrating specificity. It is thus an intriguing possibility that MGST1 function could be modulated by ligands (as well as reactive oxygen species) during oxidative stress when sulfhydryls are depleted.

Animals↗
PubMed2001

Involvement of cathepsin B- and L-like proteinases in silk gland histolysis during metamorphosis of Bombyx mori.

To identify proteinases involved in programmed cell death of the silk glands of Bombyx mori, we measured enzyme activities in silk gland homogenates. Several peptidyl-4-methylcoumaryl-7-amides (MCAs) and bovine hemoglobin were used as substrates in the presence and absence of proteinase inhibitors. The hydrolysis of t-butyloxycarbonyl-Phe-Ser-Arg-MCA (Boc-FSR-MCA), benzyloxy-carbonyl-Phe-Arg-MCA (Z-FR-MCA), and Z-Arg-Arg-MCA (Z-RR-MCA) was optimal at pH 5.5, 5.0, and 5.5, respectively. It was stimulated by the sulfhydryl compounds or EDTA and inhibited by both cysteine proteinase inhibitors and a cathepsin B-specific inhibitor, l-3-trans-(propyl-carbamoyl)oxirane-2-carbonyl)-L-isoleucyl-L-prolin (CA-074). The hemoglobin hydrolysis at the optimum pH 3.5 was inactivated by cysteine proteinase inhibitors, but stimulated slightly by pepstatin. The cleavage of Arg-MCA (R-MCA) and Leu-MCA (L-MCA) at optimum pH of 7.0 was strongly inhibited by an aminopeptidase inhibitor, puromycin, and by sulfhydryl compounds. The Boc-FSR-MCA, Z-FR-MCA, Z-RR-MCA, and hemoglobin hydrolyzing activities increased in the silk glands dramatically after cocoon formation, while the R-MCA and L-MCA cleaving activities declined. The results strongly suggest the involvement of cathepsin B- and cathepsin L-like proteinases in the histolysis of the silk gland during metamorphosis.

Animals↗
PubMed1982

Tiopronin (N-[2-mercaptopropionyl] glycin) in rheumatoid arthritis.

Two controlled trials have demonstrated that tiopronin, a new sulfhydryl compound, is active as a slow-acting antirheumatic drug in rheumatoid arthritis. One trial compared 10 patients receiving placebos and 20 receiving tiopronin, 1 gm/day; the second compared two groups of 16 patients who received either placebos or tiopronin, 1.5 gm/day. In addition, 80 patients (56 from the 2 trials plus 24 other patients) were followed up for a long period. Dropout rate for intolerance or inefficacy was comparable to that fund with D-penicillamine. Secondary toxic reactions resembled those of other sulfhydryl compounds.

Adolescent↗
PubMed1976

Comparison of mode of activation of guanosine 3':5'-monophosphate-dependent and adenosine 3':5'-monophosphate-dependent protein kinases from silkworm.

Guanosine 3':5'-monophosphate (cyclic GMP)-dependent protein kinase (protein kinase G) partially purified from silkworm pupae was selectively activated by cyclic GMP at lower concentrations. Nevertheless, the enzyme seemed to differ from adenosine 3':5'-monophosphate-dependent protein kinase (protein kinase A) with respect to the mode of response to cyclic nucleotides. The catalytic activity and cyclic GMP-binding activity were not dissociated by cyclic GMP in a manner similar to that described for protein kinase A. The enzyme was not inhibited by regulatory subunit of protein kinase A nor by protein inhibitor. A sulfhydryl compound such as 2-mercaptoethanol or glutathione was essential for the activation by cyclic GMP, and an extraordinary high concentration of either Mg2+ (100 mM) or Mn2+ (25 mM) was needed for maximal stimulation by cyclic GMP. A polyamine such as spermine, spermidine, or putrescine could substitute partly for the cation. Kinetic analysis indicated that Km for ATP was decreased whereas Ka for cyclic GMP was increased significantly at high concentrations of the cation. The effect of the cation to decrease Km for ATP was not evident in the absence of a sulfhydryl compound. These characteristics of protein kinase G described above were not observed for protein kinase A which was obtained from the same organism.

Animals↗
PubMed1983

Inhibition of Streptococcus mutans by the lactoperoxidase antimicrobial system.

Inhibition of bacterial metabolism by the lactoperoxidase (LP)-hydrogen peroxide (H2O2)-thiocyanate system was studied with representatives of serotypes a through g of Streptococcus mutans. The aims were to determine whether the amount of H2O2 released from these catalase-negative bacteria is sufficient to activate the LP system and whether these oral bacteria are resistant to inhibition by the LP system, which is active in human saliva. When the washed, stationary-phase cells were incubated aerobically with LP, thiocyanate, and glucose (Glc), greater than 90% inhibition of Glc utilization and lactate production was obtained with strains that released large amounts of H2O2 (BHT, FA-1, OMZ-176); 20 to 50% inhibition was obtained with strains that released about half as much H2O2 (B-13, Ingbritt); and no inhibition was obtained with strains that released only small amounts of H2O2 (AHT, HS-6, GS-5, LM-7, OMZ-175, 6715-15). Inhibition was most effective at pH 5, whereas release of H2O2 and accumulation of the inhibitor (hypothiocyanite ion) were highest at pH 8. With H2O2-releasing cells from early stationary phase, preincubation with Glc abolished inhibition, though it did not influence H2O2 release. Cells harvested 24 h later were depleted of sulfhydryl compounds. Inhibition of these cells was abolished by preincubation with Glc and certain sulfhydryl or disulfide compounds (reduced or oxidized glutathione, cysteine or cystine). This preincubation increased cell sulfhydryl content but had no effect on H2O2 release. All strains were inhibited when incubated with LP, thiocyanate, and added (exogenous) H2O2. Smaller amounts of H2O2 were required to inhibit at pH 5, and larger amounts were required to inhibit cells preincubated with Glc or with Glc and the sulfhydryl or disulfide compounds. The results indicate that pH, amount of H2O2, cell sulfhydryl content, and stored-carbohydrate content determine susceptibility to inhibition.

Disulfides↗
PubMed1975

A new mode of ring cleavage of 2,3-dihydroxybenzoic acid in Tecoma stans (L.). Partial purification and properties of 2,3-dihydroxybenzoate 2,3-oxygenase.

2,3-Dihydroxybenzoic acid has been shown to be oxidized via the 3-oxoadipate pathway in the leaves of Tecoma stans. The formation of 2-carboxy-cis,cis-muconic acid, a muconolactone, 3-oxoadipic acid and carbon dioxide during its metabolism has been demonstrated using an extract of Tecoma leaves. The first reaction of the pathway, viz., the conversion of 2,3-dihydroxybenzoate to 2-carboxy-cis,cis-muconic acid has been shown to be catalysed by an enzyme designated as 2,3-dihydroxybenzoate 2,3-oxygenase. The enzyme has been partially purified and a few of its properties studied. The enzyme is very labile with a half-life of 3--4 h. It is maximally active with 2,3-dihydroxybenzoate as the substrate and does not exhibit any activity with catechol, 4-methyl catechol, 3,4-dihydroxybenzoic acid, etc. However, 2,3-dihydroxy-p-toluate and 2,3-dihydroxy-p-cumate are also oxidized by the enzyme by about 38% and 28% respectively, compared to 2,3-dihydroxybenzoate. Sulfhydryl reagents inhibit the enzyme reaction and the inhibition can be prevented by preincubation of the enzyme with the substrate. Substrate also affords protection to the enzyme against thermal inactivation. Sulfhydryl compounds strongly inhibit the reaction and the inhibition cannot be prevented by preincubation of the enzyme with its substrates. Data on the effect of metal ions as well as metal chelating agents suggest that copper is the metal cofactor of the enzyme. Evidence is presented which suggests that iron may not be participating in the overall catalytic mechanism.

Cations, Divalent↗
PubMed1980

Properties of a flavoprotein sulfhydryl oxidase from rat seminal vesicle secretion.

Rat seminal vesicle secretion is a rich source of a flavoprotein oxidase that acts upon sulfhydryl compounds. The enzyme was obtained in homogeneous form as previously described [Ostrowski, M. C., Kistler, W. S., & Williams-Ashman, H. G. (1979) Biochem. Biophy. Res. Commun. 87, 171-176] and characterized with respect to prosthetic group, size, reaction stoichiometry, and substrate specificity. On the basis of its behavior during zone sedimentation, gel filtration, and electrophoresis in the presence of sodium dodecyl sulfate, it appears to be a monomeric enzyme of about 66 000 daltons. Acid denaturation liberates 1 mol of flavin adenine dinucleotide (FAD) per mol of enzyme. The reaction catalyzed was shown to be 2RSH + O2 leads to H2O2. Superoxide formation could be demonstrated. Unlike many flavoprotein oxidases, the enzyme failed to form a bleached complex with sulfite. The enzyme accepts a variety of small sulfhydryl compounds as substrates, including glutathione, cysteine, dithiothreitol, and 2-mercaptoethanol. Michaelis-Menten kinetics were obtained with these substrates providing disulfide contamination was initially eliminated by treating thiols with borohydride. The KM for glutathione was 4.4 mM with a Vmax estimated as 660 mumol per min per mg of protein. The enzyme was capable of markedly enhancing the rate of renaturation of fully reduced ribonuclease. The physiological function of the enzyme is not yet clear, though several possibilities are discussed.

Animals↗
PubMed1996

Role of glutathione modulation in acrylonitrile-induced gastric DNA damage in rats.

Acrylonitrile (VCN) or its reactive metabolites irreversibly interact with gastric DNA in vivo and cause DNA damage. The effect of glutathione (GSH) modulation on VCN-induced genotoxicity and unscheduled DNA repair synthesis (UDRS) in DNA of gastric mucosal tissues was investigated. VCN-induced UDRS was determined: in control rats, rats with depleted gastric GSH contents, and rats treated with sulfhydryl compounds. A single oral dose (23 mg/kg) of VCN induced a time- and dose-dependent increase in gastric UDRS and decrease in GSH levels. While maximal UDRS in gastric mucosa was observed 2 h following oral administration of 23 mg/kg VCN, maximal GSH depletion (50% of control) was detected 4 h following treatment. Increasing the VCN dose to 46 mg/kg caused a further decrease in gastric GSH level (27% of control), while UDRS was elevated. Inhibition of VCN oxidation by treatment of the animals with the cytochrome P450 inhibitor, SKF 525-A, prior to VCN administration caused 65% reduction in VCN-induced UDRS. Treatment of rats with the GSH depletor diethylmaleate (DEM) prior to VCN administration caused 167% increase in UDRS in gastric mucosal tissues. Treatment of the animals with the sulfhydryl compounds, cysteine and penicillamine, prior to VCN administration protected against VCN-induced UDRS. The results demonstrated an inverse and highly significant correlation between gastric GSH levels and VCN-induced UDRS (r = -0.873, P < 0.0001). In conclusion, our study indicates that VCN bioactivation and the homeostasis of gastric GSH may play a major, role in the initial processes underlying VCN-induced gastric carcinogenesis.

Acrylonitrile↗
PubMed1998

Cloning of mouse gamma-glutamyl hydrolase in the form of two cDNA variants with different 5' ends and encoding alternate leader peptide sequences.

Mouse-liver gamma-glutamyl hydrolase (GH) is a lysosomal endopeptidase with an acid pH optimum that is activated by sulfhydryl compounds and preferentially hydrolyzes the most proximal gamma-glutamyl linkage of longer chain polyglutamates of folates and their analogues. We describe the cloning of this mouse lysosomal cDNA enzyme from liver GH mRNA in the form of two cDNA variants (1.295 and 1.268 kb in length) differing 14-fold (Variant I versus Variant II) in relative frequency that exhibited 5'-end heterogeneity and encoded alternate leader peptides. The 5' UTR in these variants also differs in length by 27 nucleotides. Otherwise, the ORF and 3' UTR in each case are the same. These cDNAs encode a protein in which the deduced amino acid sequence shares 78.9 and 69. 1% identity to rat and human GH sequences, respectively. Amino acid sequence comparisons among the three species identified three conserved Asn sites and two conserved Cys residues that may be sites of glycosylation and sulfhydryl compound activation, respectively. Variant I GH mRNA was more abundant than Variant II GH mRNA in all mouse tissues examined. Variant I GH mRNA levels were extremely high in salivary gland, moderately high in kidney, liver, lung, stomach and uterus, low in small intestine, brain and fetal liver and relatively rare in thymus, spleen and skeletal muscle. Abundance of GH mRNA among tumors varied from low to high, with no discernible correlation with their tissue of origin.

Amino Acid Sequence↗
PubMed2001

Age-related changes of glutathione content, glucose transport and metabolism, and mitochondrial electron transfer function in mouse brain.

To evaluate the oxidative stress-related parameters and to determine their order of appearance in the brain aging process, radionuclide experiments were carried out on male DBF1 mice at 3, 12, 24 and 30 months of age. The content of nonprotein sulfhydryl compounds, mainly glutathione, was estimated with technetium-99m meso-hexamethyl propyleneamine oxime ([99mTc]meso-HMPAO) tissue sampling. Glucose transport and metabolism was examined with [1-14C]2-deoxy-D-glucose (2-DG) tissue sampling. Mitochondrial electron transport function was estimated with [15O]O2 gas-tissue ARG. [99mTc]Meso-HMPAO uptake in brain expressed as standardized uptake value (SUV), (radioactivity in brain tissue/tissue weight)/(total administered radioactivity/body weight), reached maximum at 12 months of age and decreased at 24 and 30 months of age in every region examined. The pattern of 2-DG, expressed as SUV, showed a tendency to increase rather than decrease with aging. [15O]O2 fixation in brain slices remained constant until 24 months, while it decreased significantly at 30 months of age. The results suggested the possibility of using imaging techniques in vivo for longitudinal evaluation of the aging process and indicated reduction of nonprotein sulfhydryl compounds including GSH at the early stages of aging may also accelerate the dysfunction of mitochondrial electron transport and neurodegeneration.

Aging↗
PubMed1951

Sulfhydryl groups in relation to the metabolism and motility of human spermatozoa.

1. The motility and metabolism of human spermatozoa are inhibited by substances which have an affinity for sulfhydryl groups. 2. These inhibitions can be prevented, and in part, reversed, by the addition to the cell + inhibitor system of sulfhydryl compounds such as cysteine or glutathione. 3. Cysteine and glutathione, under aerobic conditions or in a system in which these substances can be oxidized, show widely different effects on the motility of the spermatozoa. Cysteine destroys the motility of the spermatozoa, whereas glutathione has no effect upon it. 4. Possible mechanisms of these effects are discussed.

Cysteine↗
PubMed1995

In vitro oxidation of vitamins C and E, cholesterol, and thiols in rat brain synaptosomes.

Free radical-induced oxidation of vitamins C, E, sulfhydryl compounds, and cholesterol in brain synaptosomes from Fisher 344 rats was studied. The synaptosomes were incubated at 37 degrees C with 2,2'-azobis-(2-amidinopropane) dihydrochloride (AAPH), which undergoes thermal decomposition to yield free radicals. After incubation, the synaptosomes were sedimented, saponified, and extracted with hexane to isolate tocopherol and cholesterol. Ascorbate and tocopherol were assayed by liquid chromatography, cholesterol by gas chromatography, and total sulfhydryls by spectrophotometry. Under the in vitro conditions used in this study, the approximate order for the ease of oxidation of the various compounds was: ascorbate >>tocopherol > sulfhydryl compounds >>> cholesterol. However, tocopherol and sulfhydryl oxidation occurred even before all of the ascorbate had been consumed. Therefore, the fate of a specific antioxidant at a particular cellular location cannot be predicted with complete accuracy using the in vitro order for ease of oxidation shown here. Ascorbate may play a major role in protecting brain against oxidative damage because: (i) ascorbate concentration is high in brain, (ii) it can regenerate vitamin E from its radical oxidation product, and (iii) it is one of the first antioxidants to be consumed during oxidative reactions.

Amidines↗