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Marc Hellé

How can I calculate IC50 in DPPH test?

Adam Shakur  Follow

Dear Dr Rufayda Izzeldin,
Here's the method:
If you use are using GraphPad prism:
From the data table, click Analyze, choose nonlinear regression, and choose the panel of equations: Dose-Response -- Special, X is log(concentration). Then choose "Absolute IC50, X is log(concentration)". You must enter a value for the parameter "Baseline" on the Constrain tab of the analysis parameters dialog.
If you are using Excell:
insert a "scatter plot," and set the Y-axis to "logarithmic." It should be approximately linear over some range. Select "add trend line" and pick "exponential." Then display equation and you've got it.
Best wishes,
Sabri

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Marwan Anouar  Follow

The simplest estimate of IC50 is to plot x(concentration of extract),y (inhibition of DPPH (%)and fit the data with a straight line (linear regression). IC50 value is then estimated using the fitted line, i.e., Y = a * X + b, IC50 = (50 - b)/a.

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Andrew Constable  Follow

Plot a scatter plot graph at different concentration in excel and and fit the data with a straight line and calculate the value with y=m*x+c where y= % scavenging and x= concentration. Use y=50 and identify the concentration.

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