Thursday, December 11, 2014

Gingko or not Gingko

For many centuries, leaves from the Ginkgo biloba tree have been a common treatment in Chinese medicine. Over the last few decades an increasing number of people started to take ginkgo supplements in the belief that they will improve memory and sharpen thinking. Sales of Ginkgo biloba herbal supplements, in the United States of America, totaled more than US$25.8 million during 2012  - making G. biloba the fifth best-selling herbal supplement.

Ginkgo improves blood flow to the brain and acts as an antioxidant. These effects may translate into some benefits for certain medical problems. Some studies have shown that it can help with memory problems caused by dementia or Alzheimer’s disease and sometimes it was found to modestly boost memory and cognitive speed in healthy people. It seems to help prevent the progression of dementia symptoms, especially if the dementia is thought to be the result of atherosclerotic vascular disease. However, it does not seem to prevent dementia or Alzheimer’s in general.

There also is solid evidence that ginkgo might ease leg pain caused by clogged arteries. It might also help with some other circulation problems. Ginkgo has been studied for many other conditions, including ADHD, depression and other psychological conditions, multiple sclerosis, tinnitus from a vascular origin and prevention of high altitude sickness. However, there are currently no conclusive results that show any related benefits.

We know from earlier studies that herbal supplements on the market are often subject to mislabeling, and therefore consumers may not be getting the products and benefits they are paying for. This is a rather serious problem as there are some potential dangers of mislabeled supplements. Some adulterants are either toxic alone or in combination with other substances that are part of the supplement product. Another problem is the fact that consumers may not receive the health benefit they seek from the supplements, which might worsen their health.

A new study that just appeared in Genome presents a novel mini-DNA Barcode assay for the authentication of Ginkgo biloba in herbal dietary supplements and the author used it to estimate the frequency of mislabeled ginkgo supplements on the market in the United States. A 166-bp matK mini-barcode was designed and it unambiguously differentiates Ginkgo biloba from all other gymnosperms by the presence of a C at nucleotide position 107. All other gymnosperms have a T at this position. This new mini-Barcode seems to work quite fine and here the short form of the results:

In total, 31 of 37 (83.8%) assayable herbal dietary supplements contained identifiable G. biloba DNA and six supplements (16.2%) contained fillers without any detectable G. biloba DNA.

For the supplements in which the author found no evidence of ginkgo, it cannot be ruled out that this is because the DNA was destroyed throughout processing for example by drying at very high temperatures. However, if I understood correctly these samples did contain DNA and filler species could be identified as well. Chances are high that the samples simply did not contain any ginkgo.

It is hoped that the matK mini-barcode assay described here will be used by supplement manufacturers to ensure that their supplements not only contain the classes of compounds used for standardization but also contain Ginkgo biloba.

For the sake of any customer I would indeed hope so.

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