I researched this a bit and found there really is no standardized "cup of coffee" for research purposes. Even for volume, I've seen it range from 6 to 12 fl oz. The main mechanisms of action are caffeine and flavonoids, and there's so much variation across beans and brewing methods that you'd think researchers would try to include that in their data to normalize it.

Caffeine, flavonoids and monoamine oxidase inhibitors.