I was assuming that the antioxidant activity of plant extract will give uniform result as measured by different assays (DPPH, FRAP, and ABTS) in vitro. However, in one of my experiment, I found that the value that was increasing uniformly with DPPH assay, showed irregular trend when measured by FRAP and ABTS. Why such an irregularity is happening?
Regards,
every plant have measurement unit also compared with standard sample
Dear Tilahun..... I think every kind of test works from a different point of view, because If all routes are identical, there were no need to use more than one way, In addition to the effect of solvent on the final results, e.g. In case of DPPH test to evaluate essential oil using of methanol as a solvent will give lower antioxidant activity than dichloromethane and vice versa.
Kind Regards
Engy Maged
Hi
I think the mechanism of action is different for the several assays so different family of compouds do not react in same way.
The problems are related to the characteristics of your plant extracts (different type of compounds with different chemical structures) and, above all, to the different mechanism of action of the assay:
for example with FRAP you evaluate the ferric reducing power while with ORAC you evaluate the radical scavenging activity, so your results could be not correlated with other spectrophotometric assays (ABTS or DPPH)
Dear all,
Thank you so much for your explanations. Engy Shams, many thanks for the informative article.
Regards,
I can recommend reading my article
A. V. Ivanova, E. L. Gerasimova & Kh. Z. Brainina. Potentiometric Study of Antioxidant Activity: Development and Prospects. Critical Reviews in Analytical Chemistry, V.45, Is.4, 2015 p. 311-322.
Dear Alla,
Thank you so much. Your article was very helpful and substantial.
Regards,
This was also happened in my experiment. Honey from Syzygium guineense was found high in DPPH, and lower in FRAP. However, all other (eight) monofloral honeys do have a matching inclination in their value of DDP, FRAP and POS. This is expected to depend on the type and amounts of active compounds found in different samples, which are going to interact/scavenge the oxidants.
Good Luck
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