Detection of dideoxyosone intermediates of glycation using a monoclonal antibody: characterization of major epitope structures

Glycation or the Maillard reaction in proteins forms advanced glycation end products (AGEs) that contribute to age- and diabetes-associated changes in tissues. Dideoxyosones, which are formed by the long-range carbonyl shift of the Amadori product, are newly discovered intermediates in the process of AGE formation in proteins. They react with o-phenylenediamine (OPD) to produce quinoxalines. We developed a monoclonal antibody against 2-methylquinoxaline-6-carboxylate coupled to keyhole limpet hemocyanin. The antibody reacted strongly with ribose and fructose (+OPD)-modified RNase A and weakly with glucose and ascorbate (+OPD)-modified RNase A. Reaction with substituted quinoxalines indicated that this antibody favored the 2-methyl group on the quinoxaline ring. We used high performance liquid chromatography to isolate and purify three antibody-reactive products from a reaction mixture of N alpha-hippuryl-L-lysine+ribose+OPD. The two most reactive products were identified as diastereoisomers of N1-benzoylglycyl-N6-(2-hydroxy-3-quinoxalin-2-ylpropyl)lysine and the other less reactive product as N1-benzoylglycyl-N6-[2-hydroxy-2-(3-methylquinoxalin-2-yl)ethyl]lysine. Our study confirms that dideoxyosone intermediates form during glycation and offers a new tool for the study of this important pathway in diabetes and aging.

Nano-C60 cytotoxicity is due to lipid peroxidation

This study examines the biological effects of water-soluble fullerene aggregates in an effort to evaluate the fundamental mechanisms that contribute to the cytotoxicity of a classic engineered nanomaterial. For this work we used a water-soluble fullerene species, nano-C60, a fullerene aggregate that readily forms when pristine C60 is added to water. Nano-C60 was cytotoxic to human dermal fibroblasts, human liver carcinoma cells (HepG2), and neuronal human astrocytes at doses>or= 50 ppb (LC50=2-50 ppb, depending on cell type) after 48 h exposure. This water-soluble nano-C60 colloidal suspension disrupts normal cellular function through lipid peroxidation; reactive oxygen species are responsible for the membrane damage. Cellular viability was determined through live/dead staining and LDH release. DNA concentration and mitochondrial activity were not affected by the nano-C60 inoculations to cells in culture. The integrity of cellular membrane was examined by monitoring the peroxy-radicals on the lipid bilayer. Subsequently, glutathione production was measured to assess the cell's reaction to membrane oxidation. The damage to cell membranes was observed both with chemical assays, and confirmed physically by visualizing membrane permeability with high molecular weight dyes. With the addition of an antioxidant, L-ascorbic acid, the oxidative damage and resultant toxicity of nano-C60 was completely prevented.

Study on NO(2) absorption by ascorbic acid and various chemicals

Study on NO(2) absorption aimed at seeking a better NO(2) absorption chemical at pH 4.5 approximately 7.0 for application to existing wet flue gas desulfurization (FGD). The results from the double-stirred reactor indicated that ascorbic acid has very high absorption rate at this pH range. The rate constant of ascorbic acid reaction with NO(2) (0 approximately 1,000 x 10(-6) mol/mol) is about 3.54 x 10(6) mol/(Ls) at pH 5.4 approximately 6.5 at 55 degrees C.

Complex I deficiency primes Bax-dependent neuronal apoptosis through mitochondrial oxidative damage

Dysfunction of mitochondrial complex I is a feature of human neurodegenerative diseases such as Leber hereditary optic neuropathy and Parkinson's disease. This mitochondrial defect is associated with a recruitment of the mitochondrial-dependent apoptotic pathway in vivo. However, in isolated brain mitochondria, complex I dysfunction caused by either pharmacological or genetic means fails to directly activate this cell death pathway. Instead, deficits of complex I stimulate intramitochondrial oxidative stress, which, in turn, increase the releasable soluble pool of cytochrome c within the mitochondrial intermembrane space. Upon mitochondrial permeabilization by the cell death agonist Bax, more cytochrome c is released to the cytosol from brain mitochondria with impaired complex I activity. Given these results, we propose a model in which defects of complex I lower the threshold for activation of mitochondrial-dependent apoptosis by Bax, thereby rendering compromised neurons more prone to degenerate. This molecular scenario may have far-reaching implications for the development of effective neuroprotective therapies for these incurable illnesses.

Binary immobilization of tyrosinase by using alginate gel beads and poly(acrylamide-co-acrylic acid) hydrogels

The use of the immobilized and the stable enzymes has immense potential in the enzymatic analysis of clinical, industrial and environmental samples. However, their widespread uses are limited due to the high cost of their production. In this study, binary immobilization of tyrosinase by using Ca-alginate and poly(acrylamide-co-acrylic acid) [P(AAm-co-AA)] was investigated. Maximum reaction rate (Vmax) and Michaelis-Menten constant (Km) were determined for the free and binary immobilized enzymes. The effects of pH, temperature, storage stability, reuse number and thermal stability on the free and immobilized tyrosinase were also examined. For the free and binary immobilized enzymes on Ca-alginate and P(AAm-co-AA), optimum pH was found to be 7 and 5, respectively. Optimum temperature of the free and immobilized enzymes was observed to be 30 and 35 degrees C, respectively. Reuse number, storage and thermal stability of the free tyrosinase were increased by a result of binary immobilization.

Ascorbate stimulates monooxygenase-dependent steroidogenesis in adrenal zona glomerulosa

It is well known that ascorbic acid (Asc) is highly concentrated in the adrenal gland, but its function in the gland is not thoroughly elucidated. We therefore examined the possibility that Asc participates in steroidogenic monooxygenase systems of the adrenal cortex with the aid of the regenerating system including outer mitochondrial membrane cytochrome b (OMb). When Asc availability was limited in rat mutants unable to synthesize Asc, the increase in plasma aldosterone concentration under Na-deficiency was suppressed without effect on plasma corticosterone concentration. Aldosterone formation in the isolated mitochondrial fraction of the zona glomerulosa (zG) of the adrenal cortex was stimulated by the addition of Asc and NADH, while corticosterone formation was not. Consistently zG showed a high level of Asc regeneration activity and was rich in OMb among adrenocortical zones. Taken together, the enhanced aldosterone formation that is catalyzed by one of the steroidogenic monooxygenases, P450aldo, may be supported by Asc with its regenerating system.

[Effects of different levels of vitamin C on UV radiation-induced DNA damage]

The Raman spectra of DNA in different levels of vitamin C with 10 min ultraviolet radiation and 30 min ultraviolet radiation were reported. The intensity of ultraviolet radiation was 18.68 W x m(-2). The experimental results proved that vitamin C can reduce DNA damage solely, but the effects are related to the concentration of vitamin C. When the concentration of vitamin C was lower than 0.35 mmol x L(-1), DNA was protected better with the rising of vitamin C concentration during ultraviolet radiation. DNA was protected best when vitamin C was 0.35 mmol x L(-1). When vitamin C concentration was higher than 0.35 mmol x L(-1), vitamin C accelerated DNA damage with 10 min ultraviolet radiation. But DNA was also protected with 30 min ultraviolet radiation as vitamin C was 0.35-0.65 mmol x L(-1). However, DNA was only protected slightly at high concentration of vitamin C.

Oxidation of delta-ALA-D and DTT mediated by ascorbic acid: modulation by buffers depends on free iron

Ascorbic acid (AA) is one of the most important endogenous reducing agents and can participate in a variety of cellular events. In vitro, AA can act as a potent oxidant agent in the presence of free metals, promote modifications in protein structures and form reactive oxygen species during its oxidation. We have observed that AA (above 6 mmol/l) inactivates delta-aminolevulinate dehidratase (delta-ALA-D), a sulfhydryl-containing enzyme and that the inhibitory action was considerably decreased when 3-morpholinepropanesulfonic acid buffer (MOPS - pH: 6.8; 100 mmol/l) was used in the delta-ALA-D activity assay instead of potassium phosphate buffer (PB - pH: 6.8; 100 mmol/l). delta-ALA-D inhibition, probably, is mediated by the oxidation of -SH groups caused by the auto-oxidation of AA promoted by metals or another oxidizing system present in liver supernatants. This hypothesis was confirmed by studying dithiothreitol (DTT - 400 micromol/l) oxidation, as a model of enzyme thiols, where we observed that the mechanism underlying DTT and delta-ALA-D oxidation caused by ascorbate is the same. The difference observed between different buffers may be related to the oxidation of Fe(II) to Fe(III) that was more accentuated in PB than in MOPS buffer. The presence of ethilenediamintetraacetic acid (EDTA - 100 micromol/l) and Fe(III) (5 micromol/l) stimulated DTT oxidation more in PB than in MOPS buffer. Deferroxamine (DF - 100 micromol/l) considerably decreased DTT oxidation. Catalase (0.4 mg/ml) and Superoxide dismutase (SOD - 300 U/ml) had only a modest effect on DTT oxidation. The present results suggest that delta-ALA-D inhibition by AA is mediated primarily by the oxidized form of AA and reactive oxygen species play only a modest role in the process.

Synthesis of a Versatile (S)-3-(Hydroxymethyl)butane-1,2,4-triol Building Block and its Application for the Stereoselective Synthesis of N-Homoceramides

[structures: see text] A versatile (S)-3-(hydroxymethyl)butane-1,2,4-triol building block has been synthesized starting from D-isoascorbic acid, a common food preservative. The key transformation in this approach was the introduction of branching through a high yield and fully regioselective epoxide opening. This flexible synthon has been elaborated to a new class of (dihydro-)N-homo(phyto)ceramides.

Susceptibility of amyloid beta peptide degrading enzymes to oxidative damage: a potential Alzheimer's disease spiral

Insulysin (IDE) and neprilysin (NEP) were found to be inactivated by oxidation with hydrogen peroxide, an iron-ascorbate oxidation system, and by treatment with 2,2'-azobis(2-amidinopropane) dihydrochloride (AAPH). In each case reaction led to the introduction of protein carbonyl groups as judged by reaction with 2,4-dintrophenylhydrazine. IDE was inactivated by reaction with 4-hydroxy-2-nonenal (HNE) with the concomitant formation of protein adducts. NEP was not inactivated to a significant extent by HNE, but some HNE-adduct formation did occur. Prior reaction with hydrogen peroxide or AAPH led to enhanced formation of HNE adducts. Treatment of IDE with AAHP or hydrogen peroxide increased its susceptibility to proteolysis, while treatment of NEP with iron/ascorbate or hydrogen peroxide increased its susceptibility to proteolysis. Since IDE and NEP play a prominent role in the clearance of amyloid beta peptides, their oxidative inactivation and enhanced proteolysis can contribute to the onset and/or progression of Alzheimer's disease.

Pulse radiolysis study of the interaction of retinoids with peroxyl radicals

Vitamin A (retinol) and its derivatives-retinal and retinoic acid-are known for their ability to inhibit lipid peroxidation. Antioxidant actions of retinoids have been attributed to chain-breaking by scavenging of peroxyl radicals. Based on chemical analysis of retinoic acid degradation products formed during microsomal lipid peroxidation, it was previously suggested that retinoids interact with peroxyl radicals forming free carbon-centered radical adducts. However, it can be argued that such a mode of antioxidant action of retinoids is not sufficient to fully explain their effectiveness at inhibiting lipid peroxidation, which in many systems is comparable to, or even exceeds, that of alpha-tocopherol. In order to elucidate the mechanism of interaction of retinoids with peroxyl radicals, (trichloromethyl)peroxyl radical was generated by pulse radiolysis, and its interactions with retinoids solubilized in Triton X-100 micelles were followed by kinetic absorption spectroscopy. All retinoids--retinol, retinal, and retinoic acid--interacted with the peroxyl radical, and at least two transient products were detected. One of these products, absorbing at 590 nm, was identified as retinoid cation radical. Therefore, we postulate that, apart from formation of radical adducts, retinoids may also scavenge peroxyl radicals by electron transfer.

Histological evaluation of a topically applied retinol-vitamin C combination

Two double-blind studies versus vehicle were carried out to investigate the effects of a topically applied retinol plus vitamin C combination on epidermal and dermal compartments of aged or photoaged human skin. The two studies were performed on postmenopausal women who were selected for treatment based on the mild level of elastosis of their facial skin. At completion of treatment, skin biopsies were collected and processed for classical histology and immunohistochemistry. In the first study (aged skin), 8 volunteers applied the retinol- and vitamin C-containing preparation on the ventral side of one elbow and the vehicle on the other elbow twice daily for 3 months. After the 3-month treatment we observed histological changes mainly within the epidermis. The stratum corneum was thinner with a compact pattern, whereas the epidermal proliferation increased, resulting in a thickening of the viable epidermis. Moreover, the interdigitation index was increased. In the second study (photoaged skin), 11 volunteers were divided in two groups; one applied the retinol- and vitamin C-containing preparation and the other one the vehicle on their face twice daily for 6 months. Facial skin samples presented histologic hallmarks of photoaging, i.e. accumulation of elastotic material in the papillary dermis. After the 6-month topical treatment, the observed histological changes were mainly concentrated at the dermal level. Both treated and control groups showed the same distribution pattern of type I procollagen, however, the high level of type III procollagen originally observed in photoaged skin was reduced in the retinol- and vitamin C-treated group, resulting in a lower type III-to-type I procollagen ratio. Furthermore, a wide band of eosinophilic material just beneath the epidermis, devoid of oxytalan fibers and forming the 'grenz zone', appeared more frequently and was larger in the retinol- and vitamin C-treated group. In conclusion, our results show that repeated topical application of a preparation containing both retinol and vitamin C is able to reverse, at least in part, skin changes induced by both chronologic aging and photoaging.

A novel vitamin C analog, 2-O-(beta-D-Glucopyranosyl)ascorbic acid: examination of enzymatic synthesis and biological activity

2-O-(beta-D-Glucopyranosyl)ascorbic acid (AA 2 beta G) isolated from a popular traditional Chinese food (Lycium fruit) was synthesized using cellulase derived from Trichoderma sp. with cellobiose as a glucose donor. 6-O-(beta-D-Glucopyranosyl)ascorbic acid as well as AA 2 beta G was also synthesized in this reaction. The vitamin C activity of AA 2 beta G was also evaluated using inherently scorbutic (osteogenic disorder Shionogi [ODS]) rats. The rats were fed vitamin C-deficient food and water containing AA 2 beta G for 21. AA 2 beta G supported their growth and the level of vitamin C in tissues was moderately maintained. The vitamin C level in some tissues depended on the hydrolytic activity of AA 2 beta G (beta-glucosidase activity) although the correlation was not statistically significant (P=0.08). The results indicate that AA 2 beta G has pro-vitamin C activity.

Enzymatic synthesis of l-ascorbyl linoleate in organic media

A novel L-ascorbyl fatty acid ester, L-ascorbyl linoleate was successfully prepared by enzymatic esterification and transesterification in a non-aqueous medium using immobilized lipase as biocatalyst. Changes in enzymatic activity and product yield were studied for the following variable: the nature of the fatty acid, the fatty acid concentration and water content. The yield of synthesis for the C18 unsaturated fatty acids were higher than for the C18 saturated fatty acid. Initial enzyme concentration does not affect the equilibrium of the reaction. And the product yield (33.5%) in the transesterification was higher than that of the esterification (21.8%) at a high-substrate concentration 0.3 M. The medium water content was found to have a distinct influence on the L-ascorbyl linoleate synthesis.

Analysis of methylene blue in human urine by capillary electrophoresis

A capillary electrophoresis method for the determination of the dye methylene blue (tetramethylthionine, MB) in human urine depending on liquid/liquid-extraction and diode array detection has been developed, validated, and applied to samples of healthy individuals, who had been dosed with methylene blue within clinical studies. After extraction with dichloromethane and sodium hexanesulfonate, sample extracts were measured on an extended light path capillary. The dye was detected simultaneously at 292 and 592 nm using methylene violet 3 RAX as internal standard. The limit of quantification was 1.0 microg/ml. The accuracy of the method varied between -15.2 and +0.8% and the precision ranged from 2.0 to 12.0%. The method was linear at least within 1.0 and 60 microg/ml. In contrast to earlier indirect determinations no leuco methylene blue (LMB) was directly detected in urine, whereas in aqueous test solutions containing surplus amounts of ascorbic acid leuco methylene blue was well separated from MB in a single run.

Model studies of cholesterol and ascorbate oxidation by copper complexes: relevance to Alzheimer's disease beta-amyloid metallochemistry

The neurotoxicity of the amyloid-beta peptide (Abeta) is causally linked to Alzheimer's disease (AD) and may be related to the redox chemistry associated with its interactions with copper ions and cholesterol in brain tissue. We have used density functional theory (DFT) calculations to study the mechanism controlling the Abeta/Cu catalyzed oxidation reactions of cholesterol and ascorbate using a model system. The computed results based on a binuclear Cu complex predict that oxidation of cholesterol (yielding 4-cholesten-3-one as a specific product) proceeds at a slow rate when catalyzed by a Abeta/Cu(II)|His-|Cu(II)/Abeta) aggregate. The computed results also suggest that monomeric Abeta/Cu(II) is not able to oxidize cholesterol. DFT also predicted that Abeta will cross-link via covalent dityrosine formation during the oxidation of ascorbate but not during the oxidation of cholesterol. Experimental data were consistent with these predictions.

Ferulic acid stabilizes a solution of vitamins C and E and doubles its photoprotection of skin

Ferulic acid is a potent ubiquitous plant antioxidant. Its incorporation into a topical solution of 15%l-ascorbic acid and 1%alpha-tocopherol improved chemical stability of the vitamins (C+E) and doubled photoprotection to solar-simulated irradiation of skin from 4-fold to approximately 8-fold as measured by both erythema and sunburn cell formation. Inhibition of apoptosis was associated with reduced induction of caspase-3 and caspase-7. This antioxidant formulation efficiently reduced thymine dimer formation. This combination of pure natural low molecular weight antioxidants provides meaningful synergistic protection against oxidative stress in skin and should be useful for protection against photoaging and skin cancer.

Development of a new biosensor for superoxide radicals

A superoxide dismutase (SOD) biosensor for determination of superoxide radicals has been developed by immobilization of superoxide dismutase within gelatin (G) on a Pt electrode surface. The properties of the biosensor have been investigated and optimum conditions-enzyme concentration, glutaraldehyde concentration, and pH-were determined. The response of the G-SOD biosensor was proportional to O2*- concentration and the detection limit was 0.01 mmol L(-1) at a signal-to-noise ratio of 3. The biosensor retained 89% and 60% of its sensitivity after use for three and four weeks, respectively. Immobilization of SOD on gelatin provides a biocompatible microenvironment around the enzyme and stabilizes the activity of the enzyme very efficiently. The superoxide dismutase biosensor was used to determine the antioxidant properties of acetylsalicylic acid-based drugs and the anti-radical activity of healthy and cancerous human brain tissues.

Heterologous expression and site-directed mutagenesis of an ascorbate-reducible cytochrome b561

Cytochromes b561 (Cyts b561) are ubiquitous membrane proteins catalyzing ascorbate-mediated trans-membrane electron transfer. A heterologous expression system in Saccharomyces cerevisiae was developed to study their structure-function relationship. Recombinant mouse chromaffin granule Cyt b561 (CGCytb) shows spectral characteristics, ascorbate reducibility, and redox potentials identical to that of the native bovine protein. Moreover, the reconstituted recombinant protein mediated trans-membrane electron transport with kinetic characteristics similar to that of bovine CGCytb. Site-directed mutant analysis supports the presence of two hemes coordinated by the highly conserved His pairs H52/H120 and H86/H159. Reduction of CGCytb by ascorbate showed biphasic kinetics (Kd1: 0.016 +/- 0.005 mM, Kd2: 1.24 +/- 0.19 mM). Mutation of a well-conserved Arg residue (R72) abolished high affinity CGCytb reduction by ascorbate, indicating that this residue may be critical for substrate binding. On the other hand, mutation of a Lys previously suggested to play a role in ascorbate binding (K83), did not affect the ascorbate-mediated reduction of the protein.

Effect of Insulin on Ca2+-Dependent Hyperpolarization in Erythrocytes from Healthy Donors and Patients with Type 2 Diabetes Mellitus Accompanied by Arterial Hypertension

Insulin decreased A23187-induced hyperpolarization of the erythrocyte membrane in healthy donors. These data indicate that insulin plays a role in the regulation of Ca(2+)-activated potassium channels in human erythrocytes. However, insulin had little effect on hyperpolarization response of cells induced by artificial ascorbate--phenazine methosulfate donor-acceptor system. Addition of insulin to cell suspension from patients with type 2 diabetes mellitus did not modulate hyperpolarization of the erythrocyte membrane induced by A23187 or ascorbate-phenazine methosulfate, which reflects impairment of regulatory mechanisms for Ca(2+)-activated potassium channels in erythrocytes.

Oxidation of methyl linoleate in micellar solutions induced by the combination of iron(II)/ascorbic acid and iron(II)/H2O2

The oxidation of methyl linoleate (ML) was studied in the presence of Fe(II) alone and its combination with either ascorbic acid (AsAH(2)) or hydrogen peroxide (H(2)O(2)) at different molar ratios. Reactions were carried out in micellar solutions of TTAB (tetradecyltrimethylammonium bromide) and SDS (sodium dodecyl sulfate), respectively, and were monitored by UV spectroscopy and electrospray ionization mass spectrometry (ESI-MS). Fe(II) alone was able to catalyze the oxidation of ML in micellar solutions of TTAB, but not in those of SDS. The combination of H(2)O(2) with Fe(II) showed catalytic effect only in the TTAB medium, leading to different ML and Fe(II) oxidation kinetics compared to the Fe(II)-only catalyzed reactions. The AsAH(2)/Fe(II) combination demonstrated to be a good catalyst for the oxidation of ML in SDS micellar solutions, but not in TTAB micellar solutions; the activity of the catalyst was dependent on the AsAH(2)/Fe(II) molar ratio. The obtained results confirm that, for the ML oxidation to be initiated, the presence of a Fe(II)/Fe(III) couple is essential, which is related to the pH of micellar solutions. The catalytic properties of the AsAH(2)/Fe(II) combination were explained by taking into account the anti-oxidant and pro-oxidant properties of AsAH(2), as well as the possible formation of an iron/ascorbate complex as the initiator of the ML oxidation.

Enhanced chemical oxidation of aromatic hydrocarbons in soil systems

Fenton's destruction of benzene, toluene, ethylbenzene, and xylene (BTEX) was investigated in soil slurry batch reactors. The purpose of the investigation was to quantify the enhancement of oxidation rates and efficiency by varying process conditions such as iron catalyst (Fe(II) or Fe(III); 2, 5, and 10mM), hydrogen peroxide (H2O2; 30, 150, 300 mM), and metal chelating agents (l-ascorbic acid, gallic acid, or N-(2-hydroxyethyl)iminodiacetic acid). Rapid contaminant mass destruction (97% after 3h) occurred in the presence of 300 mM H2O2 and 10 mM Fe(III). An enhanced removal rate (>90% removal after 15 min and 95% removal after 3h) was also observed by combining Fe(III), N-(2-hydroxyethyl)iminodiacetic acid and 300 mM H2O2. The observed BTEX mass removal rate constants (3.6-7.8 x 10(-4)s(-1)) were compared to the estimated rate constants (4.1-10.1 x 10(-3)s(-1)). The influence of non-specific oxidants loss (by reaction with iron hydroxides and soil organic matter) was also explored.

Effect of surfactants on the dissociation constants of ascorbic and maleic acids

The dissociation equilibria of ascorbic and maleic acids have been studied in certain cationic, anionic and non-ionic micellar media and their pK(a) values have been evaluated by the potentiometric, conductometric and spectrophotometric techniques. These pK(a) values have been found to shift in micellar media as compared to those in pure water. The differences in the values have been attributed to the solvent properties of the interfacial and bulk phases involving contribution from the micellar surface potential in the case of charged micelles. The values of the limiting molar conductance of the acids have been determined in the various surfactants and were found to be different in different surfactants. In case of the cationic surfactants the limiting molar conductance was found to increase with increase in surfactant concentration.

Hydroxyl radical scavenging effects of guaiacol used in traditional dental pulp sedation: reaction kinetic study

Guaiacol, which is a phenolic compound with a methoxy group and used in traditional dental pulp sedation, has the property of inducing cell proliferation. To clarify these mechanisms of guaiacol, this study examined the hydroxyl radical (*OH) scavenging effects of guaiacol in vitro. Generation of *OH was carried out by the Fenton reaction using mixture of ascorbic acid, H2O2, and Fe(III)-EDTA, and *OH was detected by measuring the *OH-mediated production of degradation products of deoxyribose, which reacts with 2-thiobarbituric acid (TBA) and is relatively stable for a long time. At concentrations of 10(-10) M to 10(-3) M, guaiacol inhibited the TBA reactive substance (TBA-RS) formation in a dose-dependent manner. Phenol and formaldehyde were also found to inhibit the TBA-RS formation, but their inhibitory activities were lower than that of guaiacol. The concentrations of guaiacol, phenol, and formaldehyde needed to cause 50% inhibition of TBA-RS formation were approximately 5 x 10(-6), 5 x 10(-5), and 2 x 10(-3) M, respectively. In this reaction system, guaiacol showed no chelating reaction with ferrous ion and did not directly react with H2O2. Guaiacol also exhibited radical scavenging activity on 1,1-diphenyl-2-picrylhydrazyl (DPPH) stable free radical, but its scavenging activity was lower than that toward *OH. These results suggest that guaiacol is a potent scavenger of reactive oxygen radicals and that its radical scavenging activity may be associated with its effect on cell proliferation.

Remediation of Cr(VI) in solution using vitamin C

The effectiveness of vitamin C in treating Cr(VI)-contaminated water is being evaluated. Cr(VI) is an identified pollutant of some soils and groundwater. Vitamin C, an important biological reductant in humans and animals, can be used to transform Cr(VI) to essentially nontoxic Cr(III). The removal efficiency was 89% when the mass concentration of vitamin C was 80 mg/L in 60 min, and nearly 100% Cr(VI) was removed when the mass concentration was 100 mg/L. Our data demonstrated that the removal efficiency was affected by vitamin C concentration, the reaction temperature and the dissolved oxygen concentration. The reaction mechanism of Cr(VI) by vitamin C was presented. Our study opens the way to use vitamin C to remediate Cr(VI)-contaminated soils and groundwater.