In my research of the antioxidant activity of T. chebula, extract at a higher concentration showed less antioxidant activity than a lower concentration (0.1- 1 micro gram/ml). In a literature search, I found that antioxidants act as pro-oxidants at higher concentrations. In some study it is also reported that antioxidants at lower concentrations act as pro-oxidants. Can anybody clarify this topic?
You pose a very good question, but a difficult one to answer in such a venue. I have taught full classes on this subject, so the answer is quite in depth.
Overall, you are correct that many compounds known as antioxidants are concentration dependent. A perfect example is Vitamin C, which is been long established as an antioxidant at physiologic concentrations. But recently, researchers have shown that at very high concentrations Vitamin C (Ascorbic Acid) is a pro-oxidant, and is in clinical trials as a cancer therapy adjuvant (PMID: 22728050).
The problem in your assay is that you are using extract, which will contain various types of antioxidant and pro-oxidant molecules AND enzymes. Adding the complexity of concentration differentials in EACH one, and you can see why your data are difficult to interpret.
You obviously have started using different concentrations of the extract in treating your cells, but you may want to start examining the components of the extract soon by mass spec or HPLC. Elucidation of key antioxidant molecules will help you focus your examination, and may also help you understand optimal concentrations for therapy.
Good luck,
~Adam
Thank you Adam very much for your regards. But the problems here is to interpret the outcomes of the study. Since in literature there are both issues such as green tea extract act as prooxidant at low concentration and many other act as prooxidant at higher concentration. Well thank you very much for your support.
Hi Bhakta
Here is a very nice presentation on your topic. This will help you to clarify ur doubts to a certain extent.
GUd Luck.
Thank you Dr. Alok I am finding this file very interesting. That might be helpful for me. Thanks a lot
Are you working in vivo, or in vitro?
In vitro:
A concentration depending oxidative behavior might be related with the effect of the reagent on the pH of the environment. You might check if this is your case, if you measure the pH of the solution expressing antioxidant activity, and then change its pH. If the solution with altered pH does act as a prooxidant, then the antioxidant components of your extract might express pH-dependent AO activity.
In vivo:
The situation will be more complicated. Your extract might contain components that lead to increased activity of pro-oxidant enzymes. In law concentration of the extract these components might be not enough for boosting the activity of pro-oxidant enzymes, but at higher concentrations of the extract the effect might be more prominent.
If along with antioxidants, any compound inactivating AOE, or chemically modifying radicals scavengers, this might result in a prevalence of the pro-oxidant behavior of the extract.
The assay:
As you use a multi-components extract, there is a possibility some compound to alter conditions of the entire assay. I am sure that you made sure that this is not the case, so I just mention this possibility as such:)
I am working in the in vitro cells that is examine the antioxidant efficacy of T. chebula extract on H2O2 induced oxidative stress. I appreciate your answer, thank you very much for your answer.
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