Can you take too many antioxidents?

I eat a lot of high antioxidant foods and have now started on Mangosteen & other juices in a concentrated form. Can I get too many of these antioxidents in my system? What possible side effects might it have? I just started it the other day.

I'm also taking Elderberry concentrate to build my immune system & help with the arthritises, fibromyalgia, blood sugar levels( I'm hyPOglycemic),etc.. At the same time I am taking Prednisone to knock down my immune system so that I don't have such severe reactions to so many allergies and irratating substances and fight inflammation in my lungs and the other problems listed above I am battling. All are immune system problems with the possible Fibro which may be neurological in origin. The opinions vary on that. Is this contratictive of each other? I have thought and thought about it and decided I would get input from others. I'm not too sure the elderberry stuff isn't why I am still on my feet considering my life work load and physical stress(I hate that word). I've only been on it a couple weeks.