Please cite this article in press as: Wohlmuth, H., et al., Adulteration of Ginkgo biloba products and a simple method to improve its detection. Phytomedicine (2014), http://dx.doi.org/10.1016/j.phymed.2014.01.010 ARTICLE IN PRESS G Model PHYMED-51597; No. of Pages 7 Phytomedicine xxx (2014) xxx–xxx Contents lists available at ScienceDirect Phytomedicine jou rn al homepage: www.elsevier.de/phymed Adulteration of Ginkgo biloba products and a simple method to improve its detection Hans Wohlmuth a,b,∗ , Kate Savage c , Ashley Dowell c , Peter Mouatt a,c a Medicinal Plant Herbarium, Southern Cross University, PO Box 157, Lismore, NSW 2480, Australia b Integria Healthcare, Gallans Road, Ballina, NSW 2478, Australia c Southern Cross Plant Science, Southern Cross University, PO Box 157, Lismore, NSW 2480, Australia a r t i c l e i n f o Article history: Received 14 November 2013 Received in revised form 27 November 2013 Accepted 26 January 2014 Keywords: Ginkgo biloba Ginkgo extract Adulteration Quality control Ginkgo flavonol glycosides Genistein a b s t r a c t Extracts of ginkgo (Ginkgo biloba) leaf are widely available worldwide in herbal medicinal products, dietary supplements, botanicals and complementary medicines, and several pharmacopoeias contain monographs for ginkgo leaf, leaf extract and finished products. Being a high-value botanical commodity, ginkgo extracts may be the subject of economically motivated adulteration. We analysed eight ginkgo leaf retail products purchased in Australia and Denmark and found compelling evidence of adulteration with flavonol aglycones in three of these. The same three products also contained genistein, an isoflavone that does not occur in ginkgo leaf. Although the United States Pharmacopeia – National Formulary (USP-NF) and the British and European Pharmacopoeias stipulate a required range for flavonol glycosides in ginkgo extract, the prescribed assays quantify flavonol aglycones. This means that these pharmacopoeial methods are not capable of detecting adulteration of ginkgo extract with free flavonol aglycones. We propose a simple modification of the USP-NF method that addresses this problem: by assaying for flavonol aglycones pre and post hydrolysis the content of flavonol glycosides can be accurately estimated via a simple calculation. We also recommend a maximum limit be set for free flavonol aglycones in ginkgo extract. © 2014 Elsevier GmbH. All rights reserved. Introduction Extracts of ginkgo (Ginkgo biloba L.) leaf are sold worldwide as the active ingredient of numerous dietary supplements, botan- icals, herbal medicinal products and complementary medicines. Indeed, ginkgo is currently one of the most widely sold medici- nal plants, and the global market for ginkgo has been estimated at more than US$700 million (Euromonitor International Ltd., 2009). In the United States, the most recent (2012) data show the retail market for ginkgo products to be worth US$30 million (Lindstrom et al., 2013). Ginkgo is also one of the most intensely studied medicinal plants, with more than 3000 scientific papers published on the topic between 2001 and 2009 alone (van Beek and Montoro, 2009). Ginkgo leaf extracts are recommended for a range of conditions, including cerebral insufficiency, vertigo and tinnitus of vascular ∗ Corresponding author at: Integria Healthcare, Gallans Road, Ballina, NSW 2478, Australia. Tel.: +61 2 6620 5180; fax: +61 2 6622 3459. E-mail addresses: hans.wohlmuth@scu.edu.au, hans.wohlmuth@integria.com (H. Wohlmuth). origin, and peripheral arterial disease (Blumenthal, 2003; Bone and Mills, 2013). The pharmacologically active compounds in ginkgo leaf are considered to be flavonol glycosides (quercetin, kaempferol and isorhamnetin being the principal aglycones) and terpene lactones (bilobalide and ginkgolides). Most ginkgo leaf extracts on the mar- ket are produced by selective, multi-step extraction processes involving organic solvents and carry quantitative claims concerning their content of flavonol glycosides and terpene lactones. Accord- ingly, most ginkgo leaf extracts are more high-tech and high-cost than typical botanical extracts. Botanical raw materials including extracts present special chal- lenges in terms of quality control and assurance due to their chemical complexity and inherent natural variability. The most fundamental aspects of quality assurance for such materials are to ensure the correct morphological part(s) from the right botan- ical taxon is used, and that the material is not adulterated with other botanical or extraneous material. Adulteration, either acci- dental or intentional and economically motivated, is a well-known issue for botanicals, and one that potentially can jeopardise not only the quality but also the safety of the finished product (Khan, 2006; Walker and Applequist, 2012). The potential safety issues associ- ated with adulterated or sub-standard ginkgo extracts have been 0944-7113/$ – see front matter © 2014 Elsevier GmbH. All rights reserved. http://dx.doi.org/10.1016/j.phymed.2014.01.010