when I was measure the concentration of MDA in human platelets the kits provided had a standard (STD) known concentration. to divide sample OD/ STD OD this multiply by STD concentration 

 so , I think you must have STD concentration of MDA 

Dear Femi,

If you have used 0.5% TBA in 20% trichloroacetic acid (TCA), then you can use the protocol suggested in "KWON, T., MENZEL, D. B., AND OLCOTT, H. S. Reactivity of Malonaldehyde with Food Constituents. J. Food Sci. 30, 808 (1965)."  MDA concentration can be calculated using the Extinction coefficient of malondialdehyde at 532 nm, which is 155 mM-1 cm-1.

If you still have problem, please let me know (if you let me know absorbance value of one of your assays, I can explain taking that as an example). Please use Lambert Beer law equation.

Dear Prof. Pardha-Saradhi  

Sir, thanks so much, i really appreciate your input. Sir, i dissolved 0.288g TBA in 50 mL 90% glacial acetic acid, warm slightly and make up the volume to 100 mL with 90 % glacial acetic acid. Sir, i want to express my answer as nmol MDA/mg protein.

Here is one of my OD reading at 535 nm.

OD - 0.189

Sample protein - 28.61 mg/g

Thank you sir. 

Dear Femi,

Can you let me know the reference of protocol you are following? Authors might have given extinction coefficient of MDA-TBA complex/abduct based on their protocol. If you follow the protocol of Kwon et al., where 0.5% TBA in 20% TCA is used, then you can use the extinction coefficient of malondialdehyde-TBA at 532 nm given in their paper, which is 155 mM-1 cm-1. Extinction coefficient will vary based on reaction conditions (which include the way you are preparing reagents).

In case if extinction coefficient is 'X' mM-1 cm-1 then concentration of MDA in a sample that is showing absorbance of 0.189 would be

1/0.189 micromoles/ml [if path length is one cm and in most of the spectrophotometric measurements it is one (unless it is otherwise specified)].

I am sure you are aware that one mM MDA will have one micromole MDA/ml [one mM solution will have one mmole in 1000 ml i.e. 1000 micromoles in 1000 ml (i.e. one micromole/ml)].

If extinction coefficient is not stated in the paper, you need to prepare MDA standard curve.

Dear Prof. Pardha-Saradhi

Sir, lipid peroxidation was assayed by measuring malondialdehyde (MDA) formation as described by Sharma and Krishnamurthy (1968). extinction coefficient is 1.56 x 10 5 (raise to power of 5) M-1cm-1. 

Dear Femi,

That means  extinction coefficient is 156000 M-1cm-1 (that is156 mM-1cm-1)

OD of your sample is 0.189

0.189 = 156 x 1 x Concentration

Concentration = 0.189/156  = 0.00121154 mM = 1.21154 microM = 1211.54 nM

1211.54 nM (that means you have 1211.54 nmoles in 1000 ml). That means you have  1.21154 nmoles/ml

(as you have taken one ml of two ml solution for your assay , you need to multiply accordingly) (This is based on the information furnished by you along with your original question)

Dear Prof. Pardha-Saradhi

Sir, you are such a wonderful person with a good heart. You have really solve my problem and simplify the whole thing for me. Thanks so much sir.  

Dear Femi,

It’s my pleasure. Thanks for your compliments.

GOOD LUCK

i am getting confusion  in calculating of nmol/ml MDA in to nmol MDA /g tissue. i used okhawa method 

Dear Alok,

you need to elaborate on what sort of confusion you have. If you are in Delhi, you may visit my lab in University of Delhi.

I am very much thank full to Pro.P.Pardha Saradhi for detail information on MDA calculation. I also got cleared about this problem. Sir thank you very much.

Dear Feli, You should also devise by your protein concentration if you want your MDA expressed in nmoles/mg of proteins.

Dear prof Pardha Saradhi

Sir what is the formula for TBA calucation whether it is

TBA =Absorbance /155*weight of sample