What does the higher value of DDPH assay (higher DPPH concentration) represent when it is measured as compared to the efficiency of a Trolox standard to scavenge the DPPH free radicals?
Normally, I was assuming that a higher absorbance value of the mixture of DPPH free radical and sample extract, containing antiradical components is an indication for the presence of antioxidant compounds in less concentration within the sample extract. Less concentration of antioxidant compounds in any biomaterial extract will enable the purple color of DPPH free radical to persist for a while, which will increase the absorbance value. Accordingly, in my opinion, DPPH values are not the same with antioxidant activities. In contrary to this view of mine, I am reading different interpretations on relating DPPH values and antioxidant activities in some articles. Can you share your views, please? May you read the article in the attachment herewith as well? Thank you.
http://www.sciencedirect.com/science/article/pii/S1756464617301196
You assumed right, a higher DPPH value means the higher concentration of extract required to reduce 50% DPPH free radical. However, this is valid for IC50 values. In the article you attached, the DPPH values are expressed as Trolox equivalents, meaning that a free radical scavenging ability of the extract is compared to Trolox as the standard compound. In this way, a higher value means a better free radical scavenging ability (see https://www.jstage.jst.go.jp/article/analsci/30/7/30_717/_pdf for example). Best wishes.
Prof Robert,
Thank you so much for the explanation and the article as well. Still, it seems that your final conclusion is opposite to my assumption. If the DPPH values are higher, it means, the concentration of antioxidant compound in the extract is less. As to me, that is why the purple color of DPPH will not be turned to yellowish or colorless depending on the concentration of antiradical components in the sample extract of interest. However, to observe higher antioxidative property of our extract, I think, the colour of DPPH should not be persistent and should turn into either yellowish or color less which tells me that the antiradical compounds in the extract have quenched all the DPPH free radical up on mixing the DPPH with sample extract. Am I right? It might be misconception too, for which I request an apology in advance.
Thank you so much.
T.A.T
Hi Abera
Your conception is right. The less amount of extract is needed to decolorize the color of DPPH the more antioxidant is present in that extract.
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