Gingko Adulteration: How to Detect It

Ginkgo for Tinnitus Series

By Barry Keate
Barry Keate, has lived with tinnitus over 40 years and has published 150+ research articles on numerous aspects of tinnitus. He is an expert on the condition and a well-known advocate for those with tinnitus.

Ginkgo biloba Extract (GbE) is one of the most highly valued herbal extracts in the world. It is one of the main active ingredients in Arches Tinnitus Formula for treating tinnitus. Premium-grade ginkgo is also fairly expensive and so has become one of the most adulterated extracts in the market, targeted by unscrupulous manufacturers and fast-buck artists.

Consumer Labs reported in 2007 that 75% of ginkgo products failed testing. The question for people buying ginkgo in the health food store is: How can you tell if you are buying a quality product? The simple answer is that it is not easy. This article will describe the history and composition of ginkgo, how it’s adulterated and how the adulteration can be detected.

The American Botanical Council’s Clinical Guide to Herbs cites tinnitus, vertigo, cerebral insufficiency, and peripheral vascular disease as the primary uses of ginkgo, with other uses including hypoxia (lack of oxygen, as following a stroke), acute cochlear deafness and sexual dysfunction associated with the use of SSRI antidepressant medications.

Ginkgo achieves these results by improving blood flow to tissues, including the ears and brain, by its powerful antioxidant properties, and by neuroprotection and enhanced cellular metabolism.

The root of these actions is in the flavonol glycosides and terpene lactones found in ginkgo leaves. The primary flavonol glycosides are quercitin (Q), kaempferol (K) and isorhamnetin (I). The terpene lactones include ginkgolides (A through J) and bilobalide.

The flavonol glycosides are responsible for ginkgo’s antioxidant actions. They also increase serotonin release and reduce uptake, indications that ginkgo helps fight depression. The ginkgolide fractions of the terpene lactones support blood vessel relaxation and inhibit platelet activating factor (PAF), which is responsible for platelet aggregation, an action that causes blood to clot in the veins potentially leading to heart attack and stroke. Bilobalide has been found to be a potent antagonist to glutamate release, one of the primary culprits of tinnitus. It has also been shown to reduce the rate of GABA uptake. This keeps GABA active in the system, helping to reduce the effects of glutamate. More information on GABA and glutamate can read in Arches Tinnitus  Formula: The Science Behind the Product.

What you don’t know about ginkgo

What we have come to know as standardized 24/6 Ginkgo biloba Extract (GbE) was created in 1965 by the Dr. Willmar Schwabe Co. in Germany. This large pharmaceutical company was the first to set the standards and make the extract. It focused on a minimum of 24% flavonol glycosides and 6% terpene lactones. What most people in America are not aware of is the standard also included minimum amounts of the specific terpene lactones ginkgolide A, B and C (2.8% to 3.4%), bilobalide (2.6% to 3.2%) and mandated that there be no more than 5 parts per million (ppm) of ginkgolic acid, a toxic compound that causes gastric upset and skin rashes. There was also a standardized amount of leaves from which the extract should be derived. It is set at 50:1, meaning from 50 kg of dried leaves only 1 kg of extract is obtained.

Regulations in the US have not caught up to the detailed level of the Germans and European Union on constituent content. GbE is sold as a medicine in Germany but as a dietary supplement in the United States.

Ginkgo Approved for Tinnitus

The German government set up the German Commission E, a panel of expert physicians and scientists knowledgeable in herbal medicine, to regulate and approve herbal medications when they were shown to be effective. This panel of experts approved GbE for the treatment of tinnitus for the German people. GbE won early approval from the German government as a pharmaceutical for the treatment of vertigo, poor circulation in legs, cerebral insufficiency – memory loss related to dementia or degenerative neurological diseases such as Alzheimer’s disease. The Commission E Monograph on Ginkgo biloba can be seen in our TinnitusLibrary.

Consumer Lab Testing on Ginkgo

GbE started picking up steam in the supplement market in the late 1990’s. Independent testing organization had a business model of gravitating to the supplements most popular with consumers, so ginkgo was one of the first herbs the lab tested for quality and safety.

In 1999, ConsumerLab held finished ginkgo products to the German standards, testing them for flavonol glycoside and terpene lactone content. Of the 32 products tested, 25 passed the content test. At almost 75%, the pass rate was considered pretty good, especially for an emerging supplement in a fairly new market. However, a follow-up round of testing in 2003 generated the opposite result, about 75% failed. For products claiming to be standardized to 24/6, a 25% success rate is abysmal.

The testing also looked at lead levels and other heavy metals. A few products contained small amounts however none even remotely reached the level of safety concern. Overall, what the testing revealed was not a safety concern but one of truth in labeling and product integrity.

Ginkgo Adulteration

Ginkgo leaves naturally contain more terpene lactones than flavonol glycosides so there is rarely a problem reaching the 6% lactone content needed for the 24/6 standard. But it requires more leaves to meet the 24% flavonol glycosides, which naturally increases cost, the primary driver of adulteration. Adulteration almost always occurs in the flavonol glycosides.

The flavonol glycosides can be separated from the terpene lactones during production, which makes it easier for unscrupulous companies to simply control the terpenes to 6% while boosting the glycosides to 24% by adding a cheaper source of quercitin (Q). The primary culprit in this adulteration is rutin, because it contains 98% quercitin, but from buckwheat, an ineffective and much less expensive source. Quercitin from rutin does not have the antioxidant and antidepressant characteristics of ginkgo-based quercitin. However, it is impossible to tell the two apart with standard testing methods. While added rutin quercitin can raise the total level of flavonol glycosides to 24%, a closer analysis of each glycoside can indicate potential adulteration.

The ratio of quercitin (Q) to kaempferol (K) in the standardized GbE created by Schwabe used in clinical research consistently tested for a tight ratio range, 1.25 to 1.65 Q to K. When measuring the third glycoside, isorhamnetin (I), the range was consistently about 5:5:1 (Q:K:I).

There are many factors that influence the ratios and total yields of both the terpene lactones and flavonol glycosides. These include geography, climate, processing and, especially, time of harvest. As a result of these natural changes, the American Herbal Pharmacopeia (AHP) felt safe proposing ratios in the range of 4:4:1 to 6:5:1. Notice that Q and K are still very close to even.

In 2006, GbE supplier Ethical Naturals contracted Eurofins, an FDA-certified, independent testing laboratory, to analyze 21 samples of raw material and finished ginkgo products that were randomly chosen. About half the samples were determined to be adulterated with added flavonoids. Some products were also low in total flavonoids or terpene lactones.

Based on these tests, AHP concluded it is clear spiking with pure flavonoids compounds can be suspected for samples with Q:K ratios higher than 2.00. Some Q:K levels found in the testing were as high as 4.6:1 to 6:1.

See the Certificate of Analysis (C of A) for the ginkgo used in Arches Tinnitus Formula®. Please note the close ratio of quercitin and kaempferol, the high concentration of bilobalide and the low level of ginkgolic acid.

Caveat Emptor – Let the Buyer Beware

How is a consumer to know which are the best ginkgo products on a store shelf? The Latin term for “Let the buyer beware” is applicable here. In most cases, this is impossible to tell. Retail stores don’t have access to certificates of analysis, the laboratory results that detail the components in GbE. It is also very difficult for a consumer to get this information from the manufacturer. The best policy is to purchase from someone you know and trust to supply the best ingredients. Barring that, the general rule is you get what you pay for. Those who purchase ginkgo based on the most affordable pricing will receive an inferior product.

Unprincipled suppliers of ginkgo count on the inexperience of uninformed consumers and feed oBottle of Arches Tinnitus Formula with Ginkgo Max 26/7ff the reputation of quality products. If sales drop due to bad press, then they simply move on to the next scam. However, based on the glut of “low-priced” ginkgo available on the market it appears they may be around for some time.

Taking quality GbE is of critical importance to those of us with tinnitus. It is essential that we take an extract containing high levels of bilobalide and low levels of ginkgolic acid. It is unlikely that such ginkgo will be found in your local wholesale membership warehouse. It is found however in the ginkgo used in Arches Tinnitus Formula.