Ginkgo
Adulteration and How to Detect It
By Barry Keate
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 Relief 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 Relief 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
GbE started picking up steam in the supplement
market in the late 1990’s. Independent testing
organization ConsumerLab.com 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 Relief Formula®. Please note the close
ratio of quercitin and kaempferol, the high concentration
of bilobalide and the low level of ginkgolic acid.
Caveat
Emptor
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,
parasitical suppliers of ginkgo count on the inexperience
of uniformed consumers and feed off 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 Relief Formula®. |