I haven't actually done any chemical analyses on the before and after. Oh how I wish I could! I would love to know just exactly what does happen here.
What I can tell you is that I experience the same kind of relief no matter whether the coffee has been frozen or is fresh. I do know that there are antioxidants in freshly brewed coffee, but I don't think that comes into play here, because the coffee is cooked so long that any antioxidant activity, in my opinion, would have been destroyed already.
You may want to experiment yourself and see if it makes a difference for you whether you just use freshly made, or refrigerated for two or three days, or frozen.