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Does luminol chemiluminescence detect free radical scavengers?
M Clapperton1, J McMurray, A C Fisher
1Bioengineering Unit, University of Strathclyde, Glasgow.
British Journal of Clinical Pharmacology
|June 1, 1995
Summary
Thiol compounds like captopril and MPG reduce luminol chemiluminescence, but do not effectively scavenge superoxide radicals. This suggests luminol chemiluminescence may be unsuitable for measuring drug antioxidant activity.
Area of Science:
- Biochemistry
- Pharmacology
- Free Radical Chemistry
Background:
- Thiol compounds' ability to scavenge superoxide (O2-) and hydrogen peroxide (H2O2) is debated.
- Previous studies conflict on whether thiols effectively neutralize reactive oxygen species produced by hypoxanthine/xanthine oxidase.
Purpose of the Study:
- To investigate the discrepancy in reported thiol compound reactivity towards reactive oxygen species.
- To determine if captopril and MPG scavenge oxidants generated by the hypoxanthine/xanthine oxidase system.
Main Methods:
- Assessed the effect of captopril and MPG on hypoxanthine/xanthine oxidase-induced luminol chemiluminescence.
- Measured thiol oxidation in captopril and MPG after incubation with hypoxanthine/xanthine oxidase.
- Monitored urate production and oxygen consumption by xanthine oxidase.
Main Results:
- Captopril and MPG reduced luminol chemiluminescence but showed minimal thiol oxidation (7% and 20% respectively).
- These compounds did not inhibit xanthine oxidase activity, evidenced by unchanged urate production and oxygen consumption.
- The observed chemiluminescence quenching is independent of direct oxidant scavenging by the thiols.
Conclusions:
- Captopril and MPG are ineffective scavengers of reactive oxygen species produced by the hypoxanthine/xanthine oxidase system.
- Luminol chemiluminescence may not be a reliable method for evaluating the free radical scavenging capacity of certain drugs.