In all antioxidant assay for calculation below mentioned formula is used
% of Inhibition = CONTROL O.D - Sample O.D/ CONTROL O.D X 100
But, In this case I got negative result of sample because Control O.D is lesser than sample O.D. In a Control I take all reagents and sample plant extracts is added for estimation.
Is it right way of experiment???
Please guide me either I am going on right path of experiment or not??
Disha,
Yes, you can consider negative results in antioxidant assay. Actually few compounds work via redox pathway so they work just opposite to antioxidants. Few compounds are antioxidant at certain conc. whereas preoxidant at other. These compounds demonstrate their anticancer activity by generating ROS. The best example is Vitamin C, read the article in provided link
http://www.scientificamerican.com/article/study-suggests-vitamin-c/
Your assay may not properly standardise,,,Have a look to attached articles and standardise the assays,,,All the best...
Thank you Sir, I refer it and resolve my problem. This article will help me for my work.
Hi Disha
Please have a look at these papers regarding antioxidant activity determination by various approaches. Another thing, you should also focus on the inherent antioxidant activity which your mixture and ingredients may have. This may also add to the measured absorbance. In that case, you will have to subtract the inherent activity from the measured one to get the correct readings. Feel free to ask if you have any query later.
Regards
Your extracts are too diluted so it its reduction rate is too less. So any small error during experimentation gives negative results... So first of all increase concentration of extracts and also try to reduce experimentation or handling error.
Hi Disha, I'm not sure what assays you are doing. But perhaps the colour of your samples is affecting the assay. You may need to do a colour blank as well as this will eliminate such a problem.
Hi Disha, though you have not mentioned what antioxidant assay you are doing.. But you may try DPPH. Its easy and reliable.. Moreover its not a mistake to get negative antioxidant results. Try flavonoids, sometimes a flavonoid rich compound doesn't give much of positive antioxidant result. Check my papers for both methods.
Hi Disha, I have attached a PPT regarding total phenol and antioxidant (DPPH) assay. This may possibly be found helpful:
Dear Disha, 1st check the type of antioxidant activity you are processing and repeat it not less than five times. Please feel free to ask me once again.
Here is a related thread with interesting contributions from RG friends
https://www.researchgate.net/post/Did_anyone_record_negative_IC50_value
Please follow the same procedure in my following article its very easy & correct
Disha,
Yes, you can consider negative results in antioxidant assay. Actually few compounds work via redox pathway so they work just opposite to antioxidants. Few compounds are antioxidant at certain conc. whereas preoxidant at other. These compounds demonstrate their anticancer activity by generating ROS. The best example is Vitamin C, read the article in provided link
http://www.scientificamerican.com/article/study-suggests-vitamin-c/
Can anyone help me how to calculate percent inhibition for FRAP assay
Dheeraj Shootha are you working on Ferric Reducing Antioxidant Power?
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