Ginkgo adulteration ‘very widespread’, say industry experts, so why is awareness low?


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“As a measure of cGMP it is the responsibility of the manufacturers to take adequate steps to address the quality and efficacy (and safety) of the nutraceutical ingredients used in formulation besides quantity” – Chandra et al. J. Funct. Foods.
“As a measure of cGMP it is the responsibility of the manufacturers to take adequate steps to address the quality and efficacy (and safety) of the nutraceutical ingredients used in formulation besides quantity” – Chandra et al. J. Funct. Foods.

Related tags Ginkgo Adulterant

Adulteration of Ginkgo biloba is ‘very widespread’, according to industry sources, but as the adulteration becomes more sophisticated new methods are emerging to help industry ensure the quality of this key herbal.

Ginkgo biloba​ is one of the herbal industry’s big players, with data from the ABC Herb Market Report for 2011 (using SPINS data for the sale of single ingredient Ginkgo extracts) putting the US Ginkgo market at an estimated $18.4 million ($4.1 million in the natural health foods channel, and $14.3 million in the food drug and mass market channel). The global market is reported to be worth $1 billion.

It is estimated that 50 kg of dried ginkgo leaf is required to make one kg of extract, and the extract is expensive and complex to manufacture. Since costs are so high, there have been numerous reports of adulteration of ginkgo extracts dating back decades. The most common form of adulteration has been the use of quercetin and rutin to artificially enhance the flavonol glycoside content. 

Ginkgo extracts are typically standardized to contain a minimum of 24% flavonol glycosides, 6% terpene lactones, and less than 5ppm ginkgolic acids.

Japanese Pagoda

Roy Upton from the American Herbal Pharmacopoeia (AHP) said he believed the issue of ginkgo adulteration to be “very widespread”​, with a 30-50% cost difference between suppliers. “Adulteration with rutin or quercetin is very prevalent in the marketplace.”

While many in the industry are now aware of the rutin issue, a study by Amitabh Chandra from Amway Corp. et al. in the Journal of Functional Foods​ (2011, Vol. 3, pp. 107-114), highlighted the relatively new practice of using extracts from Sophora japonica​ fruit (Japanese pagoda tree).

“It is interesting to note that ginkgo extracts classified as ‘adulterated’ have a profile that is very similar to Sophora extracts,” ​wrote Chandra et al. “They both have quercetin and rutin as the only components. This makes Sophora extract a viable natural adulterant for ginkgo extracts.”

Under review

Surveys of the quality of ginkgo-containing products have found that as many of 70% of products may be adulterated, although Mark Blumenthal, Founder and Executive Director of the American Botanical Council (ABC), questioned how representative these samples were. Regardless of this, “any amount of adulterated products is unacceptable,”​ he said.

The Chandra article was the subject of an HerbClip from the ABC in April 2013. Blumenthal told us that the Council initially missed the 2011 publication, as its collaborative ABC-AHP-NCNPR Botanical Adulterants Program​ was just beginning at that time.

“We have over 5,300 Herbclips and they are focused on clinical trials and meta-analyses,”​ he said. “Because of our commitment to educate stakeholders regarding adulterants, we thought it appropriate to put the ginkgo issue back on the table.”

Ginkgo is being lined up as the focus of a review for the Botanical Adulterants Program later in 2013.

Blumenthal cautioned that the collaboration has not yet confirmed the use of Sophora​, but the data he has seen to date is “very suggestive and not inconsistent with economically motivated adulteration”.


Cal Bewicke, President of Ethical Naturals, Inc. (ENI), told us that the company has developed a method to detect adulteration with Sophora japonica​.

The company produced a PhytoReport​ in May 2013, which is being circulated within the industry. Bewicke said: "Ethical Naturals’ intention is help resolve this problem within our industry; to this end we are open to sharing our work and analytical method with other companies who share this goal."

The PhytoReport​ details a simple method to distinguish between pure Ginkgo extract, pure Sophora​ extracts, as well as Sophora​ and rutin adulterated Ginkgo extracts.

The method is very simple, said Bewicke, and is a HPLC analysis with an altered wavelength to optimize for genistein. This is done because the genistein peak in pure ginkgo extract is low (internal tests showed a range of 0.03% to 0.1%). However, for pure Sophora​ or Sophora​ and rutin adulterated Ginkgo extracts, the genistein is 8% and 3%, respectively.

ABC’s Blumenthal welcomed the ENI initiative: “Hopefully, the ENI method is repeatable and reasonable. If it is, this could be a significant contribution.”

‘Ignorance and cost’

If such simple methods are available, why isn’t this being done? “The simple reasons are cost and ignorance,” ​said AHP’s Upton.

“From a QC perspective, not everyone is doing the appropriate analysis, and it depends how the specs have been written. If it’s ‘ginkgo extract with 24% flavonol glycosides’ then that’s all will be tested for.

“If a lab is asked to test for 24% flavonol glycosides, an absence of Sophora, and test to ensure a lack of spiking with rutin and quercetin, then you have a much better chance of catching it.”

“I guarantee that a very small number of marketers of ginkgo include those disclosures,” ​he added. “They are asking for a test of 24% flavonol glycosides. If it passes, it passes.”

‘It will take a warning letter’

Upton said that he has been aware of Sophora​ spiking for three to four years, and it has been discussed in identity studies. “But there are never enough people talking about it.”

“The marketers are not necessarily reading the geeky analytical studies. Most companies buying ginkgo in the marketplace do not have the technical training.”

Some labs are already testing for the presence of Sophora​: Elan Sudberg, CEO of Alkemists Labs in California, told us that his lab does see ginkgo adulteration in the marketplace, although infrequently. Identification is done using HPTLC, he said.

“It is the case that other botanicals are used to bolster the rutin content to meet unreasonable and mostly irrelevant specs.  We combat this by running multiple accessions of authenticated Ginkgo leaf alongside the test sample and, on occasion, ​Sophora japonica fruit.” 

So what happens next? “It’s up to the FDA, I believe,” ​said Upton.

“As soon as the FDA takes appropriate action, the industry should be aware that ginkgo can be adulterated, therefore you must conduct the positive test to ensure it’s ginkgo and the negative tests to ensure absence of pure flavonol glycosides and/ or Sophora.

“I think it will take a warning letter,” ​he said.

ENI's Bewicke agreed that an FDA warning letter would go a long way to resolving the problem, "however fortunately there are many well-intended companies out there who strive to do the right thing by their customers, with or without an FDA warning, even if it puts them at a cost disadvantage"​, he added.

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