Ginkgo biloba L. (GB) is one of the top-selling herbal products in the world. The extract of GB
used in commercial preparation is often standardized to 24% of flavonol glycosides
and 6% terpene lactones. Being a high-value herbal (medicinal) product, GB extracts
may be a subject for economically driven adulteration.
In [1] we reported that of 35 GB products (containing extracts and plant material)
from the UK market only two show the HPTLC fingerprint that described in the Ph. Eur.
and USP monographs for Ginkgo extract. All others contain high levels of quercetin,
rutin, or additional zones not characteristic of GB.
Aiming at a better characterization of the adulterants, additional detection modes
were evaluated and another derivatization step was added to the original HPTLC method
for identification. Beside added rutin and/or quercetin, the modified method detects
added Buckwheat and Styphnolobium japonicum (L.) Schott (SJ – syn.: Sophora japonica L.) fruit prior to derivatization as well as SJ flower after derivatization. Additional HPTLC methods were established to verify
the levels of quercetin (NMT 0.5%) and the presence of genistein as marker for SJ fruit.
Samples were also assayed for total flavonoid glycosides by HPLC according to the
USP and Ph. Eur monographs on Ginkgo leaves and extract. Twelve samples were in compliance
with the total amount of flavonol glycoside specified in the monographs. However,
ten of those had elevated levels of quercetin in HPTLC fingerprint. This was confirmed
with an additional HPLC limit test for rutin and quercetin described in the ginkgo
extract monograph from USP.
With the proposed modified HPTLC method for identification of GB several types of
adulteration can be detected without additional chromatography. That significantly
saves cost in a routine setting.
[1] Booker A, Frommenwiler D, Reich E, Horsfield S, Heinrich M. J Herb Med 2016; 6:
79 – 87
