Nasir: Its is the same calculation that you use for IC50 determination for any drug. First, perform a dose response experiment, various concentration of your plant extract versus scavenging of DPPH radical. Then use the linear regression to calculate the dose/concentration required for 50% reduction of the DPPH radical.IC50 value can be calculated using the fitted line, i.e., Y = a * X + b, IC50 = (0.5 - b)/a.
Draw the curve as mentioned in the picture Fig. 4 (please see the link below for pic). And find out the value of 'x-axis' as 50 % scavenging of DPPH.
http://www.sciencedirect.com/science/article/pii/S2095177915000131
If you have the DDPH radical scavenging values at different concentrations you can calculate IC50 by using R-program
Please go through this paper V
egetable and fruit peels as a novel source of antioxidants
K Rakholiya, M Kaneria, S Chanda
J Med Plant Res 5, 63-71
Please see the attached video.
Hope it would help..
https://www.youtube.com/watch?v=JaO7hrZ7b4Y
I think that the following papers maybe useful.
http://www.sciencedirect.com/science/article/pii/S2095177915000131
https://molpharm.aspetjournals.org/content/molpharm/early/2019/02/15/mol.118.115220.full.pdf
(wileyonlinelibrary.com) DOI: 10.1002/pst.426
DPPH inhibition (%)={(A0 –A1)/A0}×100 where A0 is the absorbance of control and A1 is the absorbance of test.
For standard test 1.0 mL of various ascorbic acid solutions (100 μg/mL) and gallic acid solutions (10 μg/mL) were used in place of sample extract.
In DPPH free radical scavenging method, IC50 (Half maximal Inhibitory Concentration) value is the concentration of the sample that could scavenge 50% of DPPH free radical.
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