We have ROS such as O2•−, OH•, H2O2,and 1O2. The ROS scavengers are NADPH, Uric acid, Vitamin A, Vitamin C, Vitamin E, Glutathione, Beta-carotene and polyphenols, etc. In these, which is more powerful scavengers to ROS. Is there any selectivity? what is the order of scavenging ability of above bio-molecules?
Please share your knowledge and Thank you in advance.
Dear
Antioxidants have two known mechanism of action first is chain breaker and the second is the elements blockers. However H2O2 is not a free radical. All mentioned bioactive compounds have high antioxidant properties but they are more effective in different parts of the body, for example vitamin C is effective in polar parts but vitamin E is more effective in fat witch can be absorbed well. However the intake of these secondary antioxidant have a great impact on health as they help the primary antioxidant extract e.g. glutathione peroxidase and catalase.
In addition to Alsiddig's answer: as far as I know, there is no scavenger for the hydroxyl radical because it is too short-lived. When it is formed it immediately reacts with a molecule in its vicinity.
Regards, Christian
I Thank Christian & Alsiddig. So the hydroxyl radical is easily react with a vicinity molecule (whatever it is)?
Dear Gopi,
yes, the hydroxyl radical wants to get rid of its surplus electron as quickly as possible. The only way to detoxify it is scavenging by antioxidants like glutathion or melatonin.
Cheers, Christian
As Mr. Kalaiyarasan points out, there are different oxidants - one is actually a mild reductant, the name ROS is a misnomer - which react at different rates with different molecules, see the NIST chemical kinetics database, http://kinetics.nist.gov/kinetics/index.jsp. The efficiency of scavenging is determined by the product of rate constant and concentration of the antioxidant. Furthermore, you cannot compare fat-soluble and water-soluble antioxidants. There is thus also no "best" scavenger. The thermodynamic properties of these radcials and molecules have been compared, see the attachment.
No, the hydroxyl radical does not want to get rid of its surplus electron, because it does not have one. It would like to add to a molecule or to oxidise it.
Hope it helps,
Willem H. Koppenol
@ Mr. Koppenol: Thanks for the correction!
Regards, Christian
I agree the answer of Willem H Koppenol. In additiont the efficiency of scavenging ROS is determined by the total antioxydant activity of enzymatic and non enzymatic antioxydants.
Glutathione oxidoreductase and thioredoxin disulfide reductase can scavenge the ROS potentially by HAT based mechanism. because, both enzymes have dithiol redox active site.
In context of this topic, I would like to bring to your attention a recent review of our group, "Functions of ROS in macrophages and antimicrobial immunity". In this review, we give an introduction to ROS and their sources in macrophages, summarize the versatile roles of ROS in direct and indirect antimicrobial immune defense and provide an overview of commonly used ROS probes, ROS source inhibitors and ROS scavengers (also the difference between ROS scavengers and antioxidants, which are not synonymous, is explained). If you like, please have a look at:
Article Functions of ROS in Macrophages and Antimicrobial Immunity
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