Using non-linear curve fitting: fit all experimental data to a curve with y = % response vs control (ideally y ranges from about 0 to about 100%) and x = log concentration.
Fitting can be done with stat packages (Systat, GraphPad, Curve Expert: https://www.curveexpert.net/) or with a small shareware (http://curveexpert.software.informer.com/1.3/). See enclosed paper for possible sigmoidal equations to use.
In order to calculate IC50 you need to know the initial concentration of your extract ( g plant material/ mL of solvent ). after that you will prepare 3 concentrations from you extract and mesure the % of inhibition of DPPH. From the equation of the graph you obtained %DPPH=a [c] +b ( for IC 50 the % of inhibition is 50 ) IC50 = (50-b)/a
Thank you for your answers by the way i think that the equation of Inhibition% = f ([extract]) you have found a right curve on the other hand a given moment will arrive at a precise time a saturation therefore if you do y = ax + b don you will have more than 100 % Inhibition of tone radical where it is not right. C is almost like the catalytic rate curve of an enzyme depending on its substrate or km = v max / 2 = Ic50
- Badges
- Science topic
- Similar topics
- Applied Mathematics
- Calculations