Total antioxidant capacity in plants from Phosphomolybdenum assay.
Hello ramesh,
I think you would have carried out with different concentrations of your samples. Have you calculated standard. if not do the assay for standard too. you can use ascorbic acid as the standard and compare your extract values along with standard. Calculate IC 50 value for the samples.
How to calculate the % of inhibition:
For example:
Control OD : 0.532 ; Sample OD : 0.216.
To calculate % of inhibition:
% of inhibition = control OD - sample OD/ Control OD X 100.
= 0.532 - 0.216 / 0.532 X 100 = 59.36
Its not only phosphomolybdeum assay gives you the result of total antioxidant capacity for your plant. You can try for ABTS method also. this assay also gives the total antioxidant capacity.
Hi Leeba,
Thanks for your valuable reply to Mr. Ramesh. But I have got 1 question here :
Total antioxidant capacity and IC 50 are different right, as:
Total antioxidant assay - to analyse the cumulative antioxidant capacity;
IC 50 - the concentration of an antioxidant at which 50 % inhibition of free radical activity is obtained.
For IC 50 the above mentioned method is appropriate , but for total antioxidant capacity ???
For eg :
lets say the OD of X (sample) = 0.046 ; The linear eqn obtained for Ascorbic acid standard is
y = 0.2385 x - 0.054
therefore, x = (y- 0.054 )/ 0.2385
In the above equation the y has to be substituted by our sample OD values.
the cumulative of the substituted values will gives us the total antioxidant capacity (TAC) value.
The trickiest part here is the conversion,
for eg ;
you are taking the sample at various concentration say 50 ug/ml , 150 ug/ml ......250 ug/ml.
After substituting the OD value in the equation obtained for Ascorbic acid standard ,
we get the "X" value ,
NOW THE QUESTION IS :
If I want to express the "X" value i.e., (ug/ml) in mg/g , what should be done to express our "X" value as "Total antioxidant capacity equivalent of ascorbic acid was ------ mg/g of extract" ????
First you try to make a standard curve at different conc. by taking standard antioxidant compound for eg., gallic acid or alpha tocopherol. then by taking your O.D you can express your result equivalent to that standard
Thank you every one for information, in this case i got higher ABS of sample compare to Control, if we subtract value from Positive control like having Ascorbic acid, Gallic acid than fine I got positive ans but if I proceed with negative control having only reagents than I got Negative result please suggest me Either I have take Positive control or Negative control??
How can we make a standard curve of Ascorbic acid to calculate total antioxidant capacity in plants using Phosphomolybdenum assay? we have to add the a mixture of the reagent solution (0.6M sulfuric acid, 28mM sodium phosphate and 4 mM ammonium molybdate) to Ascorbic acid at different conc or not?
Absorbance of the Ascorbic acid standards solution is measured at 695 nm against blank as the samples?
I would like to know if the sodium phosphate is monobasic or dibasic and at what pH.
I have used gallic acid as standard but have got the sample O.D greater than Control O.D...What to do in this case?
How can I calculate the total antioxidant capacity (TAC) from IC50 of DPPH ?
thank you.
Am interested in this question 'I would like to know if the sodium phosphate is monobasic or dibasic and at what pH.… '. Do anybody have an answer to that question?
Do we calculate IC50 after getting total antioxidant capacity value from the Phosphomolybdenum assay
The control tube contains the respective solvent and reagent,hence when heated the tube becomes transparent. Then how come we calculate the% inhinition for phosphomolydenum assay?
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