Wikipedia lists coffea arabica as a plant species with a high theobromine content, but does not include coffee on the list of significant dietary sources. I searched around, and it looks like the theobromine content in coffee is essentially zero. How can this be? Is all the theobromine contained in parts of the plant other than the beans? Maybe it is removed by the extraction process?
According to the Dr. Duke's Phytochemical and Ethnobotanical Databases, Coffee Arabica has one of the largest amount of theobromine in its seed (20 ppm). However, this amount is just a bit more than 1/2500 th of the amount what Cocoa includes (48 223 ppm). So... Coffee is not really considered a theobromine source, but Cocoa is.
I suspect the reason is that theobromine is much less soluble in water than caffeine. A forum post is here.
- Caffeine – 21600mg/L water
- Theobromine – 330mg/L water
So potentially the grounds have theobromine but it doesn't dissolve during brewing.