The effect of buffers and chelators on the reaction of luminol with Fenton's reagent near neutral pH

Bottu, Guy

doi:10.1002/bio.1170060303

Cited by 13 publications

(10 citation statements)

References 13 publications

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“…The following 0.1 mol/L buffers were used at different pHs: sodium acetate (pH 4.0, 4.5, 5.0 and 5.5); sodium citrate (pH 6.0, 6.25, 6.5 and 6.75); potassium phosphate (pH 7.0, 7.25, 7.5, 7.75 and 8.0); sodium borate (pH 8.25, 8.5, 9.0 and 9.5); and sodium carbonate (pH 10.0 and 10.5). Initially sodium diethyl barbiturate was used at pH 8.0 and 8.5, but we found that this buffer had scavenger abilities, confirming the findings of Bottu (9,10).…”

Section: Methodssupporting

confidence: 80%

The effect of pH on chemiluminescence of different probes exposed to superoxide and singlet oxygen generators

Oosthuizen¹,

Englbrecht²,

Lambrechts³

et al. 1997

J. Biolumin. Chemilumin.

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The compromised optima for high intensity chemiluminescence (CL), using superoxide generators, were all above pH 9.0 for the CL probes luminol and lucigenin. With luminol the optima were at pH 9.0 and 9.4 for the generators KO2 and hypoxanthine/xanthine oxidase (HX/XO), respectively. Lucigenin, with the same generators, produced optima at pH 9.5 and 10.0, respectively. The probe methyl-Cypridina-luciferin analogue (MCLA) produced optima closer to neutral pH, which is preferred for physiological assessments. MCLA had optima at pH 6.0, 8.7 and 9.5 with KO2 and with HX/XO optima at pH 4.8, 6.0, 7.0 and 8.7. When CL was assessed at physiological pH, MCLA observed superoxide radicals with a sensitivity of 100- and 330-fold more than luminol or luicigenin respectively. For singlet oxygen, the sensitivity of MCLA at this pH was 45- and 5465-fold more than for the said probes respectively. H2O2 did not elicit CL between pH 4 and 9.5 with any of the probes and did not influence the production of superoxide or singlet oxygen when co-assessed. Therefore CL could only be obtained when enzymes were used as converters. The optima for the enzyme-conversion system horseradish peroxidase (HRP)/H2O2, and luminol, were at pH 8.0 and 9.2. Lucigenin and HRP/H2O2 also had a biphasic CL profile with optima at pH 7.4 and 9.6. MCLA and HRP/H2O2 had five optima, with the major ones at pH 6.1 and beyond 10. The optima for the myeloperoxidase/H2O system were at 8.6 and beyond 10.0 when luminol and 0.15 mol/L NaBr were used.

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Section: Methodssupporting

confidence: 80%

The effect of pH on chemiluminescence of different probes exposed to superoxide and singlet oxygen generators

Oosthuizen¹,

Englbrecht²,

Lambrechts³

et al. 1997

J. Biolumin. Chemilumin.

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“…Aqueous solutions of divalent transition metal cations such as Cu 2+ , Fe 2+ , Co 2+ , and Mn 2+ are well known to catalyze the chemiluminescence of luminol in the presence of dissolved O 2 and/or H 2 O 2 . − In the presence of H 2 O 2 , significant increases in emitted light intensity may be produced by even trace concentrations of transition metal cations . The exact mechanism of this transition metal catalysis is not known but the production of HO • through a Fenton type reaction has been suggest as an important step, i.e., It is also known that the complexation of divalent transition metal cations by chelating agents such as EDTA greatly diminishes their ability to catalyze luminol chemiluminescence. , On the basis of the above it is first proposed that the levels of background light emission observed in the absence of added EDTA result from luminol chemiluminescence catalyzed by traces of transition metal cation present in the reagents and/or water used in our experiments. Metal cations leaching from apparatus and glassware could also contribute.…”

Section: Resultsmentioning

confidence: 99%

“…The study of luminol SCL in the presence of H 2 O 2 is potentially complicated by a background (nonsonochemical) process of chemiluminescence catalyzed by trace concentrations of divalent transition metal cations. − Transition metal contamination of solutions through impurities present in reagents or through leaching from equipment is difficult to avoid completely. However, chelating agents such as EDTA are known to complex the cations involved, greatly reducing their catalytic activity. , Here we show how EDTA may be used to suppress the background chemiluminescence of aqueous solutions containing luminol and H 2 O 2 while minimally affecting SCL, thus simplifying the acquisition of SCL intensity data.…”

Section: Introductionmentioning

confidence: 99%

Mechanistic and Spatial Study of Ultrasonically Induced Luminol Chemiluminescence

1999

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Aqueous solutions containing 10-3 M luminol and varying concentrations of hydrogen peroxide are irradiated with 20 kHz ultrasound at 50 °C. The intensity of sonogenerated chemiluminescence (SCL) is shown to increase linearly with ultrasound power and to be strongly pH dependent, reaching a maximum at pH 12. For pH < 10 SCL intensity (I SCL) is independent of H2O2 concentration. For pH >10 I SCL increases monotonically with H2O2 concentration up to10-4 M but decreases as the concentration is increased further. A mechanism is proposed in which HO2 - and the luminol monoanion competitively reduce sonochemically generated HO•, producing O2 •- and luminol radical anion, respectively. Luminescence follows the decomposition of a hydroperoxide adduct formed by reaction between O2 •- and luminol radical anion. EDTA is shown to suppress the background (silent) chemiluminescence of solutions containing luminol and H2O2 without significantly affecting I SCL. Digital images of SCL emission occurring near the transducer−solution interface are analyzed to determine the spatial distribution of sonochemical activity. It is shown that, in the absence of standing waves, I SCL decays exponentially with perpendicular distance from the surface of a plane-ended ultrasound transducer horn. Spatially resolved I SCL data is used to determine the acoustic attenuation coefficient (α) in acoustically cavitating water noninvasively. It is shown that α values at the cavitation-producing frequency increase with transducer output power and may be many orders of magnitude greater than is the case for homogeneous water.

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“…Therefore, the first step in this study was to ensure that the experimental conditions were optimal and that they did not generate artifacts. Ethanol acts as an • OH scavenger under some experimental conditions [26]. We investigated the effect of ethanol in reducing DNA damage induced by Cr(III) plus H 2 O 2 .…”

Section: Discussionmentioning

confidence: 99%

Melatonin, xanthurenic acid, resveratrol, EGCG, vitamin C and α‐lipoic acid differentially reduce oxidative DNA damage induced by Fenton reagents: a study of their individual and synergistic actions

López‐Burillo

Tan

Mayo

et al. 2003

Journal of Pineal Research

145

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: DNA damage generated by oxygen‐derived free radicals is related to mutagenesis, carcinogenesis and aging. In the last several years, hundreds of publications have confirmed that melatonin is a potent endogenous free radical scavenger. In the present in vitro study, we have examined the efficacy of three polyphenolic antioxidants, i.e. xanthurenic acid, resveratrol (3,4′,5‐trihydroxy‐trans‐stilbene) and (−)‐epigallocatechin‐3‐gallate (EGCG) and two classical non‐polyphenolic antioxidants, i.e. vitamin C (ascorbic acid) and α‐lipoic acid (LA, 1,2‐dithiolane‐3‐pentanoic acid) in inhibiting •OH‐induced oxidative DNA damage. We compared the efficacy of these five antioxidants with the effectiveness of melatonin (N‐acetyl‐5‐methoxytryptamine) and we also investigated the possible synergistic effects of melatonin with the other five molecules. Using high performance liquid chromatography (HPLC), the formation of 8‐hydroxy‐2‐deoxyguanosine (8‐OH‐dG) in purified calf thymus DNA treated with the Fenton reagents, chromium(III) (as CrCl3) plus hydrogen peroxide (H2O2) (Cr(III)/H2O2), was measured in the presence or absence of the antioxidants alone or in combination with melatonin. 8‐OH‐dG is considered a biomarker of oxidative DNA damage. Among the antioxidants tested, melatonin was the most effective of these with an IC50 = 3.6 ± 0.1 μm. For the other antioxidants the IC50 values were as follows: xanthurenic acid (IC50 = 7.9 ± 0.3), resveratrol (IC50 = 10.9 ± 0.3), EGCG (IC50 = 5.7 ± 0.3), vitamin C (IC50 = 16.9 ± 0.5) and LA (IC50 = 38.8 ± 0.7). These values differ from that of melatonin with a P < 0.01. Melatonin (1 μM) reversed the pro‐oxidant effect of resveratrol (0.5 μM) and vitamin C (0.5 μM), had an antagonistic effect when used in combination with EGCG (1 μM) and it exhibited synergism in combination with vitamin C (0.5 μM) and with LA (5 μM).

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The effect of buffers and chelators on the reaction of luminol with Fenton's reagent near neutral pH

Cited by 13 publications

References 13 publications

The effect of pH on chemiluminescence of different probes exposed to superoxide and singlet oxygen generators

The effect of pH on chemiluminescence of different probes exposed to superoxide and singlet oxygen generators

Mechanistic and Spatial Study of Ultrasonically Induced Luminol Chemiluminescence

Melatonin, xanthurenic acid, resveratrol, EGCG, vitamin C and α‐lipoic acid differentially reduce oxidative DNA damage induced by Fenton reagents: a study of their individual and synergistic actions

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