I am testing the potential of olive leaves extracts as natural antioxidants in food applications (meat products) by inclusion of different concentrations of olive leaves extracts in the meat samples and compare it with negative control sample (without antioxidant) and positive control sample ( with a conventional chemical antioxidant), but I got strange results. In the first one week, the amount of MDA in the samples with olive leaves extracts is lower than the negative control which is expected and reflecting the antioxidant ability of the extracts (giving lower MDA amounts), but after one month, strange results obtained where the amount of MDA in the samples treated with olive leaves extracts is higher than the negative control which is not expected at all.
So any idea about the interpretation of these results?
Perhaps, the lipids of the olive extracts are oxidized after one month and they contribute for the TBARS increment.
You can test the pure olive extracts (without any food application) measuring their TBARS after: a) one week and b) one month, at the same conditions of your experiment.
Thanks a lot Dr. Zervoudakis for this valuable information, but I also tested a pure antioxidant (oleuropein which is the main phenolic compound in olive leaves) and got the same results, so do you think that oleuropein is oxidized and gives this increment in the TBARS.
I am not sure but If you observe that TBARS are increased in your oleuropein extract after one month, I believe that the extract contributes for the total TBARS increment.
I also suggest that you can have another control if you add the conventional chemical antioxidant (of the positive control sample) together with the olive extract and measure TBARS after one week amd one month (with and without food application).