In addition to the therapeutic parameters noted in each of the monographs, every monograph includes implied standards for quality, according to the current issue of the German Pharmacopoeia ( DAB ). However, a few of the more recently published Commission E monographs contain specific standards for assessing the quality of the herbal drug (Busse, 1996). These include the monographs for Ginkgo Biloba leaf dry extract, Horse Chestnut seed extract, and Lecithin. Since the early 1990s Commission E has issued an increasing number of monographs on specifically defined plant preparations. "This was due to further improvements in the analytical procedures applied for quality control of plant preparations (e.g., extracts). It was shown that differing methods of manufacturing (e.g., the use of different solvents for extraction, purification steps) resulted in extracts of different quality. The results from pharmacological and clinical trials with one extract could thus not automatically be transferred to another preparation." (Busse, 1996). A good example of this process is the Commission E monograph on Ginkgo Biloba leaf dry extract, based on several patented, standardized extracts of a 50 to 1 average concentration, with chemically defined standardization for ginkgolides (6 percent) and ginkgo flavonglycosides (24 percent), and a maximum level of ginkgolic acid (max. 5 ppm). In spring of 1997, the Bf ArM sent a letter to manufacturers of phytomedicines requiring proof that all ginkgo extracts have less than 5 ppm ginkgolic acid in order for products to receive license renewals, due to concerns about the potential allergenic effects of ginkgolic acid (Thiele, 1997).

Regarding research conducted on proprietary preparations like the ginkgo extracts described above, if a manufacturer is able to document the same bioequivalence (or phytoequivalence , as it is often called for plant medicines) in addition to the chemical profile, then these results may be transferable to a claim for a preparation (Schilcher, 1997b). No new pharmacological or clinical studies are required; however, the documentation must demonstrate phytoequivalence via in vitro pharmacokinetic studies (Schilcher, 1998a).