Antonije D. Žunić You may wish to look at biomarkers of oxidative stress such as MDA, 4-HNE, 8OHdG. These are commonly used biomarkers to measure oxidative damage resulting from oxidative stress. With that said, you can also look at antioxidant levels (SOD, catalase, GPx). I highly recommend you to read "Free Radicals in Biology and Medicine" by Barry halliwell and John M. C. Gutteridge. This book is considered a standard read/highly regarded in the free radical biology field.