Ginkgo Quality Story

The ginkgo flavonglycosides (ginkgo flavone glycosides) of Ginkgo biloba, comprising quercetin, kaempferol and isorhamnetin are the phytochemicals most often referred to as indicators of quality and efficacy. However, these compounds are mainly marker compounds which are used to identify the extract. The clinically active ingredients are believed to include the ginkgolides and bilobalide, which cannot be tested by normal HPLC methods. They require more sophisticated methods of detection such as Refractive Index (RI), Evaporative Light Scattering Detectors (ELSD) or Mass Spectrometry (MS). MediHerb uses ELSD detection to accurately quantify the levels of these clinically important phytochemicals. The other important group of phytochemicals from Ginkgo are the ginkgolic acids (C13:0, C15:1 and C17:1 on the third figure). These compounds have been identified as contact allergens. The maximum level of ginkgolic acids in Ginkgo biloba extracts has been set by the European authorities at 5 ppm. Many poor quality extracts contain levels of ginkgolic acids which are many orders of magnitude higher than this recommended maximum.