Study finds widespread adulteration of grape seed extract

By Hank Schultz contact

- Last updated on GMT

Authentic grape seed extract is a side product of the wine industry.
Authentic grape seed extract is a side product of the wine industry.

Related tags: Grape seed extract, Adulterant

Grape seed extracts have been showing up in increasing numbers in the dietary supplements marketplace driven by their connection with blood pressure support and other health benefits. But are all of these extracts what they seem to be? A recent paper in the journal Food Chemistry raises serious doubts.

Titled “Chemical investigation of commercial grape seed derived products to assess quality and detect adulteration,” ​the paper looked at 21 commercially available grape seed extract (GSE) supplements. GSE is a complex mix of proanthocyanidin monomers and oligomers and other chemicals, the authors noted. “Given no standardized criteria for quality, large variation exists in the composition of commercial GSE supplements,”​ wrote the paper's authors.

The authors said that the paper arose out of wider effort to evaluate GSE for the treatment of Alzheimer’s disease and the mitigation of cognitive memory loss. A wide variability was found when vetting GSE vendors during that process. 

The authors set out to develop a TLC technique to look at the 21 extracts (purchased from a variety of outlets, including online) to see whether any of them were adulterated. Peanut skin extract and pine bark extract are two other materials that contain similar proanthocyanidins (PACs). Using reference materials for peanut skin extract and pine bark extract, the authors submitted the 21 samples to the test.  Their results were sobering.

Overall, the quality of commercially available GSE products was low.  “Very few of the commercial GSE samples contained an overall content of PACs and catechins at a level comparable to authentic GSE, which raises a serious concern,”​ they wrote.

And adulteration was rampant.  “Overall six of the commercial samples could be considered seriously adulterated, perhaps counterfeit, while another five samples contained considerably less PACs and catechins than the remaining commercial samples,”​ they wrote.

The six worst samples appeared to consist almost entirely of peanut skin extract. The adulteration issue notwithstanding, this could be a serious concern as peanuts are a very dangerous potential allergen, the authors wrote.

Surprising result

GSE adulteration has flown under the radar until recently, said Stefan Gaftner, PhD, chief science officer of the American Botanical Council.

“The first time I was made aware of that problem was early October at a botanical conference,” ​Gafner told NutraIngredients-USA. “I was surprised, because grape seed extract is already a side product of the wine industry, so I would think that plenty of grape seeds would be available.  But there must be a financial incentive, so my conclusion would be there must be an even greater abundance of peanut skins.”

ABC is a the forefront of industry stakeholders looking into the adulteration of botanical materials. ABC operates the Botanical Adulterants Program in conjunction with the American Herbal Pharmacopoeia and the National Center for Natural Products Research.

Gafner said that while the adulteration of GSE cannot be condoned, it’s not necessarily the case that the resulting product has no health benefits. “I would say based on the chemistry, some of the benefits you get from grape seed extract you might also get from peanut skin extract.  But with peanut skin extract, there are no studies I am aware of on their health benefits,” ​he said.

And, curiously, Gafner said that GSE has itself been used as an adulterant. A Spanish study found cranberry extract that was adulterated with grape seed extract, he said. “So it goes both ways;  grape seed extract can be adulterated and grape seed extract can itself be an adulterant,”​ he said.

More sophisticated tests

The paper’s authors said more sophisticated tests are needed to detect this type of adulteration. 

“Due to reliance on inferior proximate assays across the value-chain, adulteration can then go undetected by others downstream in the commodity chain, such as those involved in distribution, packaging, wholesale, and retail sales. The inherent problem is that many of these manufacturers, relying on inferior quality control procedures, do not know their products may be adulterated or counterfeit, leading to the perpetuation of low quality products in the marketplace.

“The purpose of this study is to demonstrate the necessity of chromatographic techniques (TLC, HPLC, etc.) for the screening of grape seed extract for quality and adulteration. Only with chromatographic techniques can one differentiate between the components common to GSE, and peanut skin extract,”​ they wrote.

Source: Food Chemistry
Volume 170, Pages 271-280
“Chemical investigation of commercial grape seed derived products to assess quality and detect adulteration"
Authors: Tom S. Villani, William Reichert, Mario G. Ferruzzi, Giulio M. Pasinetti, James E. Simon, Qingli Wu 

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1 comment

How to avoid adulteration in PFS: the PlantLIBRA Project

Posted by Chlodwig FRANZ, Prof. Dr.,

Within our EU-Project PlantLIBRA we dealt with identification and authentication of herbal materials for plant Food supplements and developed DNA as well as chromatographic methods for a high number of plants. Finally, the European Botanical Forum, now Food Supplements Europe, presented recently a Guideline (2 Vol.) 'Quality of Botanical Preparations' (Oct. 2014). Quality control of PFS is absolutely necessary!

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