Jordan W. , Mar 09, 2006; 10:30 p.m.
Denton -- Coffee has all kinds of polyphenols in it, and I think that it is those that are the main "antioxidants" (in the biological sense) in coffee -- and I think they are present in wine and tea as well.
But the main reducing agent (in the photographic sense) in coffee is thought to be caffeic acid, which is unrelated to caffeine. You sound like you're a chemist -- so you'll know what I mean when I say that it exists as a glycoside in the coffee bean, but the parent acid is (IIRC) 3,4-dihydroxycinnamic acid. That ortho-dihydroxylated aromatic ring is what's doing the developing -- just like catechol does.
AFAIK caffeine on its own is not a strong enough reducing agent to develop film. I think I remember reading (here or at APUG) that someone actually tried developing film in a solution of No-Doze, and that it did not work.