Botanical Adulterants Monitor: Issue 20, September 2020

Unclear Reason for Deviations in Ginkgo Leaf Extract Fingerprints

The American Botanical Council and BAPP have been alerted to the sale of ginkgo (Ginkgo biloba, Ginkgoaceae) leaf extracts with an uncharacteristic fingerprint in the region of flavonol aglycones (quercetin, kaempferol, isorhamnetin) prior to hydrolysis. The high-performance thin-layer chromatography (HPTLC) data, provided by Sidney Sudberg at Alkemist Labs, shows a chromatographic fingerprint that complies with authentic ginkgo reference standard, except for the zones of quercetin, kaempferol, and isorhamnetin, which is similar to Japanese sophora (Sophora japonica, syn. Styphnolobium japonicum, Fabaceae) flower extracts. According to the supplier of the material, this fingerprint is a result of the use of AB-8 resin to selectively concentrate flavonol glycosides.¹

Comment: This case illustrates the sometimes difficult task of authenticating ginkgo leaf extracts by chemical means. Adulteration of ginkgo leaf extracts with flavonoid-rich extracts, especially extracts from Japanese sophora, has been widely reported in the literature.² More stringent specifications, e.g., limits in the contents of rutin (< 4%) and quercetin (< 0.5%) prior to hydrolysis, and ratios of quercetin-kaempferol and quercetin-isorhamnetin in the United States Pharmacopeia (USP) monograph for ginkgo extracts³ are attempts to provide appropriate tools to prevent fraudulent suppliers to sell their materials. However, new manufacturing processes, and the natural variability in the composition of ginkgo leaves may lead to situations where authentic ginkgo leaf extracts are rejected, if they do not comply with the more stringent specifications. On the other hand, more sophisticated efforts to adulterate ginkgo leaf extracts may lead to situations where adulterated extracts still pass the USP monograph. At the end of the day, it is the product manufacturer’s responsibility to set ingredient specifications for the identity, contents of declared ingredients and marker compounds, and limits for contaminants as required by dietary supplement current Good Manufacturing Practices, and to verify that the purchased ginkgo extracts comply with the specified composition.

References

1. Zhang L, Wu T, Xiao W, Wang Z, Ding G, Zhao L. Enrichment and purification of total ginkgo flavonoid O-glycosides from Ginkgo biloba extract with macroporous resin and evaluation of anti-Inflammation activities in vitro. Molecules. 2018;23(5):1167.
2. Gafner S. Adulteration of Ginkgo biloba leaf extract. Botanical Adulterants Prevention Bulletin. Austin, TX: ABC-AHP-NCNPR Botanical Adulterants Prevention Program; 2018:1-8.
3. Powdered ginkgo extract. USP 43-NF 38. Rockville, MD: United States Pharmacopeial Convention; 2020:5038.