We measure ROS using special oxidant-sensitive

probe DCHF-DA  to assess the intracellular ROS levels in P.

expansum. 

You can use DHE for superoxide determination and CellRox for total ROS.

Perhaps ELISA test will be helpful, for example this http://www.jaica.com/e/products_dna_8ohdg_kit_hs.html

8-hydroxy-2'-deoxyguanosine (8-OHdG).

For nitrotirosine Cayman have also ElSA KITS and for total antioxidant status for example kits from Randox  (TAS) (it is simple colorimetric test)