testing antioxidants

[casey22]

How do I test antioxidant activities in tomatoes? I have tried the tomato juice on an apple to see how long it takes to brown but it didnt work at all. Is there a kit I can buy to test antioxidant activity in tomatoes? I need to know asap!

[koppol]

You can test the effect of tomato extract (juice) on stopping the browning process of apples or avocados and compare with lemon juice. The tomato juice should stop the browning process not induce it (I thought you tested how long did it test to brown. Well, tomato juice is acidic, it will “denature” the enzymes that will react with the phenols released by the apple when you cut it, stopping the reaction so the apple won’t become brown).
For the following tests you will need chemicals and a chemistry professor to help you and guide you
One of the tests include:
DPPH Free radical Scavenging assay: DPPH- in this method if there is an antioxidant, the purple color intensity of DPPH (2,2-diphenyl-2 picrylhydrazyl) solution decays and there is a change in absorbance. In this method take 0.15 mM solution of DPPH prepared in methanol. Add 2 ml of this solution to 1 ml of methanol extracts of the fruit you want to test. The control is done by taking 2 ml of DPPH and adding 1 ml of methanol (no fruit extract). Mix the tubes, let them stand for 30 min and then measure the absorbance at 517 nm.
There is an essay (you will need help from your chemistry teacher)- it is called the TEAC (Trolox equivalent antioxidant capacity assay. It is based on the ability of the antioxidants to be able to quench radicals. You will need a spectrophotometer to measure the absorption and compare it to Trolox.
Another assay: ABTS (J. Ethnopharmacol. 2003. 84(2-3): 131-138
Babbar, N. Oberoi, H.S. Uppal, D.S. and Tumadu, R.P. 2011. Total phenolic content and antioxidant capacity of extracts obtained from six important fruit residues. Food Research International 44(1): 391-396.

[casey22]

thank you so much!