A medicinal product authorization application requires comprehensive information on origin and quality of an active substance. What information is required was defined in two Guidelines so far: the Guideline "Chemistry of Active Substances" (3AQ5a) from 1987 and the "Guideline on the Chemistry of New Active Substances" from 2004.
http://www.gmp-compliance.org/enews_05704_EMA-issues-new-Guideline-on-%22Chemistry-of-Active-Substances%22.html