From a link posted by
@relistan this table shows the ingredients of roasted coffee beans:
Coffee, one of the most popular beverages in the world, contains many bioactive compounds. The aim of this study was a comparative evaluation of the content of bioactive compounds in organic and conventional coffee (Coffea arabica) originating from Brazil during 12 months storage. The content of...
link.springer.com
The main component is chlorogenic Acid.
With increasing pH and time in water the chlorogenic Acid=5-CQA breaks down to quinicic acid =QA and caffeic Acid=CA, fig 3, LHS.
Originally I found that caffeic acid was not as active as coffee:
Caffeic acid is often mentioned as the possible developing agent in the instant coffee based developer Caffenol: http://caffenol.blogspot.de/2010/03/caffenol-c-m-recipe.html I compared the activity of Caffenol-C-M with that of a similar solution in which the 40g/L instant coffee (Lidl Arabica)...
www.photrio.com
This may be due to leaving out quinicic acid and possibly other ingredients in
@relistan's table.
The main active substances in caffenol would then be caffeic acid and quinicic acid plus minor ingredients from the table, plus ascorbic acid if added.