I have plotted a graph on excel between % inhibition and plant concentration (1,0.5,0.25,0.125 mg/ml). The values of percentage inhibition are (92.042,80.407,74.479,42.01). How can i determine IC-50 now? Guide please.
You can draw an histogram and get the trend line with regression equation in Excel. Then put y=50 and calculate the x value using the regression equation. The x value is the IC50 of DPPH.
So far I think, your data is not ok for calculating DPPH as it is not dose-dependent. If I calculate the IC50 value using these data it would be -0.0143, which is not correct. As 0.125 mg/ml inhibited 42.01% so 0.5 was supposed to inhibit 100%. Please repeat this experiment to get standard data. If need more help, please write to the inbox.
I agree with Mr MD, the IC50 means the concentration used that represent 50%inhibition activity. The result you've got not accurate. The best way check your data or / and repeat the experiment.
Hello Marwa and Md.Shahinozzaman
I discussed these reading with my professor and she says these reading are ok. Because when we calculate IC50 of a plant through regression equation it does not give always accurate value for 50% inhibition. secondly , plants bioactive compounds dont behave mathematically.As 0.125 mg/ml inhibited 42.01% so 0.5 was supposed to inhibit 100%.
What to do now? plz share
I am also agree with your professor. If you can get at least three inhibition values- one is around 50%, one is below 50%, another is higher than 50%, then the regression line would be perfect to calculate the IC50 value. In this case, I suggest you to repeat your experiment with 0.1 mg/ml, 0.2 mg/ml and 0.5 mg/ml concentrations. Along with your sample, you also need to check the positive control like BHT. After that, I think you will get the good data and also the good idea for DPPH assay.
ok thanks sir,
I will let you know then.
what about this formula
(Y-Y1)(X-X1)=(Y2-Y1)(X2-X1)
Dear Shazia,
You can read: EC50 estimation of antioxidant activity in DPPH assay using several statistical programs (http://www.sciencedirect.com/science/article/pii/S0308814612016020)
Can anyone pass comment on the attached image Md. Shahinozzaman Shazia Kanwal Azeemi
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