Adulteration
of Grape Seed Extract (Vitis vinifera)
By Steve Kupinaa and Stefan
Gafner, PhDb*
aPolyphenolics, Madera, CA 93637 bAmerican Botanical Council, Austin, TX 78723
*Corresponding
author: email
Keywords:
Vitis
vinifera, grape seed
extract, adulterant, adulteration
Goal: The goal of this bulletin is to
provide timely information and/or updates on issues of adulteration of grape
seed extract (GSE†) to the international herbal products industry
and extended natural products community in general. It is intended to present the
available data on the occurrence of adulteration, the market situation, and
consequences for the consumer and the industry.
1
General Information
1.1
Common name: Grape2
1.2
Other common names:
English: European grape, wine grape2
Chinese: Pu tao (葡萄)
French: Raisin
German: Traube, Weintraube
Italian: Uva
Spanish: Uva
1.3
Accepted Latin binomial: Vitis vinifera L.2
1.4
Synonyms: Cissus vinifera (L.) Kuntze3,4
1.5
Botanical family:
Vitaceae
1.6
Plant part and extract production method: The seeds of grapes, obtained as a by-product from the
juice or wine industry, are used fresh, or more commonly dried, to produce a
liquid extract using a solvent (e.g., water, or mixtures of water with ethanol
or acetone), which is filtered, and may be subjected to further processing
before it is typically spray-dried to obtain a dry extract containing high
levels of naturally occurring grape seed phenolic compounds.
1.7
General use(s): GSE
is known as a dietary
ingredient and a number of commercial materials have received self-affirmed “generally
recognized as safe” (GRAS) status as a food additive; it contains phenolic
compounds with antioxidant properties for use in dietary supplements,
nutritionally enhanced beverages, and functional foods. The most significant application for
GSE is as an ingredient in dietary supplements (known as “food supplements” in
some countries outside the United States).
2
Market
2.1 Importance in the trade:
Due to the widespread history and
acceptance of grapes and wine, GSE has received acceptance almost globally as
an ingredient for human consumption. It is one of the more widely used
botanical extracts, due to increasing scientific findings supporting health
benefits. However, it remains a specialty item relative to global commodities. In
the United States, GSE has ranked among the top 20 best-selling dietary
supplements in the Food, Drug and Mass Market channel (excluding sales at
Walmart) from 2008-2011, but not in 2012, with sales between US $1.4 million and
$2.8 million.5-9 Sales in the Mainstream Multi-Outlet channel (the
new name for the Food, Drug and Mass Market channel) were down to US $1.1 million
and $0.9 million in 2013 and 2014, respectively, ranking GSE at 67th in 2014.
Sales in the Natural channel (excluding sales at Whole
Foods Market, a major natural products retailer in the US) were US $1.5 and $1.3 million in 2013
and 2014, respectively, with GSE ranking 59th in 2014 (T. Smith [American
Botanical Council] e-mail to S. Gafner, September 3, 2015). (See Table 1)
Table 1: Sales data for grape seed
extract dietary supplements in the United States from 2012-2014.
Channel
|
2011
|
2012
|
2013
|
2014
|
|
Rank
|
Sales [US$]
|
Rank
|
Sales [US$]
|
Rank
|
Sales [US$]
|
Rank
|
Sales
[US$]
|
Naturala
|
n/a
|
1,553,155
|
52
|
1,481,374
|
55
|
1,518,647
|
59
|
1,327,495
|
Mainstream
Multi-Outletb,c
|
17
|
1,261,907
|
37
|
3,468,122
|
64
|
1,075,951
|
67
|
900,560
|
aAccording
to SPINS (SPINS
does not track Whole Foods Market sales, which is a major natural products
retailer in the US) bAccording to SPINS/IRI
(the Mainstream Multi-Outlet channel was formerly known as food, drug and mass
market channel [FDM], exclusive of possible sales at Walmart, a major retailer
in the US and beyond). n/a: not available cData for 2012 are
according to Symphony/IRI and include Walmart, club stores (Sam’s, Costco),
military and dollar stores Source: T. Smith
(American Botanical Council) e-mails to S. Gafner, September 2, 2015 and
September 3, 2015, and reference 9.
2.2
Market dynamics: GSE was at the height of its popularity in the early 2000s,
with global sales of US $60 million in 2000.10 According to
data from Nutrition Business Journal,
sales in 2011 were approximately $25 million.10 The largest US
producer of GSE is Polyphenolics, a division of Constellation Brands. Other key
players in the market (in the United States and internationally) include
Indena, Naturex, and Nexira. A number of Chinese manufacturers, e.g., Skyherb
and JF Natural, are also active in the US GSE market. The primary application
for both Europe and United States is dietary/food supplements.
2.3
Supply sources: GSE is
supplied by all major grape-producing countries and regions; the main producers
are the United States, Canada, Europe, South America, South Africa, and Australia.
2.4
Raw material forms:
GSE is almost exclusively supplied to dietary supplement manufacturers
in the form of a dry extract. The extract contains phenolic compound concentrations
ranging from ca. 50-90% of the extract and sometimes there is further
characterization of the phenolic compounds. The main phenolic compounds are
flavan-3-ol monomers and polymers and their gallic acid esters. The polymers
are known as proanthocyanidins (PACs); the term oligomeric proanthocyanidin (OPC) is not well defined in the sense
that the number of monomer units in an oligomer varies among authors, but most
often it is limited to a maximum of 10 units. Grape seeds contain predominantly
B-type PACs, which are flavan-3-ol polymers where the units are linked by a
single bond (Figure 1). The extract has a characteristically bitter and
astringent taste. Various companies manufacture their own GSE from purchased
grape seeds. Intentional adulteration of GSE can occur at the extraction
facility in order to artificially increase the concentration in total phenols
and to increase the volume by using other PAC-rich substances (see Section 3
below). Contract manufacturers for the dietary supplement and food industries
purchase bulk dry GSE extract and produce dietary supplements and/or beverages.
Figure 1: Chemical structures of the predominant proanthocyanidins
in GSE12
3
Adulteration
3.1
Known adulterants: Peanut
(Arachis hypogaea, Fabaceae) skin
extract, pine (Pinus spp.,
Pinaceae) bark, green tea (Camellia
sinensis, Theaceae) extract, and PAC (proanthocyanidin)-rich (e.g.,
propelargonidin-containing) extracts from non-grape seed sources.1,13
Propelargonidins, a particular type of PAC, are found in the
following plants and plant materials: raspberry (Rubus idaeus subsp. idaeus
or R. idaeus subsp. strigosus, Rosaceae), strawberry (Fragaria vesca or F. virginiana, Rosaceae), common beans (Phaseolus vulgaris, Fabaceae), almond (Prunus dulcis, Rosaceae), cinnamon (Cinnamomum verum, Lauraceae), buckwheat (Fagopyrum esculentum, Polygonaceae), mountain ash (Sorbus aucuparia, Rosaceae) berries, hops
(Humulus lupulus, Cannabaceae), and green
tea.14-18 The fact that the species above contain propelargonidins
does not mean that they have been used as adulterant of GSE.
3.2 Sources of information confirming adulteration:
There are at least four reports (one publication and three conference
presentations) on GSE adulteration to date. Villani et al. analyzed the PACs in
authentic GSEs, pine (Pinus spp., Pinaceae) bark, and
peanut (Arachis hypogaea, Fabaceae) skin extracts, and in 21 commercial
GSE products that were obtained from a variety of sources, including
dietary supplement retailers, supermarkets, and online vendors.1 Overall,
in six of the commercial samples, GSE was considered to be substituted with
peanut skin extract, while an additional three samples showed evidence of admixture
of an ingredient containing A-type PACs, inconsistent with the chemical profile
of GSE. Based on the evaluation of the HPLC-LC/MS profile, the adulterant appears
to be peanut skin extract. Cases of adulteration of commercial GSEs with
peanut skin extracts were also presented by Sudberg et al. (2014)19 The results were similar
to those of the Villani study.1
In addition, evidence for GSE adulteration was presented in lectures at two
conferences. One lecture reported on the detection of PACs (e.g.,
propelargonidins) from non-grape seed sources in products labeled as GSE,13
while the other exposed a case of GSE spiking with gallic acid and
epicatechin.20
3.3 Accidental or intentional
adulteration: The motivation behind purposeful adulteration in commercial
products is financial gain and to increase the concentration in PACs (aka
economically motivated adulteration). Peanut skin extract, which
is a high-volume byproduct of the peanut industry, is less expensive and
typically available at a much greater volume than GSE. In the United States, a
typical peanut mill may produce up to 17 tons of peanut skins per week, and the
material sold for as little as US
$0.02/kg in 2009.21 For example, in China, in 2015, the price for peanut skin
extract was at US $10-13/kg, pine bark extract at US $20-22/kg, and GSE at US $30-35/kg,
although proprietary GSEs may be sold for up to US $110/kg (X. Jin, overseas
sales manager at the dietary supplement manufacturer Skyherb, e-mail to S.
Gafner, August 31, 2015). Thus, a bulk distributor of GSE or another
manufacturer along the value chain can take advantage of the chemical
similarity between GSE and peanut skin extract since the spectrophotometric
assays typically used in industry are not specific
enough to discriminate between grape seed PACs and PACs from other plant
extracts. Due to reliance on non-specific proximate assays across the
value-chain, adulteration can go undetected downstream in the commodity chain,
such as those involved in distribution, packaging, wholesale, and retail sales.
3.4
Frequency of occurrence:
There is limited data available on the extent of the adulteration from the available
studies. Villani et al., analyzed 21 commercial GSE
products that were obtained from dietary supplement retailers
and supermarkets in the United States, and from online vendors, and concluded
that nine products (43%) had evidence of adulteration with peanut skins.1
In the study by Sudberg et al., out of the five commercial GSEs analyzed by high-performance thin layer
chromatography (HPTLC, Figure 2), four extracts (80%) showed bands that
are characteristic of peanut skin extract.19 Using the same HPTLC
approach, testing of 254 commercial GSE samples performed by Alkemist Labs,
a contract analytical testing laboratory, between August 2014 and January 2016
found the presence of peanut skin extract in 67 (26%) samples (H. Johnson
e-mail to S. Gafner, January 22, 2016). This
suggests that GSE adulteration in the market is not uncommon.
3.5
Possible safety/therapeutic issues:
The
adulteration of GSE with peanut skin extracts has the potential to be damaging to
consumers and the dietary supplement industry. Peanuts are a common allergen worldwide.
Because of this, the US Food Allergen Labeling and Consumer Protection
Act requires that all packaged food products sold in the United States
that contain peanuts as an ingredient must list the word “peanut” on the label.
Any peanut-containing or peanut extract-containing product that is not labeled
accordingly creates a situation in which the consumer is not only deceived by
buying a product that is not what it is purported to be, but due to the
allergenic potential of peanuts in general (even if the allergenicity of
processed peanut skins is lower than that for peanuts themselves),22,23
it also represents a potential safety risk. In the United States alone, the
prevalence of people sensitive to peanuts or tree nuts was estimated to be 1.4%
in 2008.24 The self-determined prevalence of peanut allergies
worldwide ranges from 0% in 18-month-old children from Iceland to 15% for a
group of 15–17-year-olds from France.25 Considering that peanut
skin extract contains compounds similar to those in GSE, it is not known if
efficacy is compromised.
3.6
Analytical methods to detect adulteration: There are only a few published methods for the
detection of GSE adulteration. High-performance thin-layer chromatography (HPTLC)
was successfully used to detect adulteration with peanut skin extract.1,19
Figure
2: HPTLC analysis of authentic GSE (lanes 1-2), mixtures of GSE and peanut skin
extract (lanes 3-12), authentic peanut skin extract (lanes 13-14), and the
standard compound catechin (lane 20). Concentrations for extracts were ca. 100
mg/mL, and 0.5 mg/mL for catechin. Image courtesy Alkemist Labs; Costa Mesa,
CA.19
Villani et al., also used
high-performance liquid chromatography with ultraviolet and mass spectrometric
detection (HPLC-UV/MS) to obtain a chemical fingerprint of grape seed, peanut
skin, and pine extracts.1 While both analytical approaches
allowed the distinction between grape seed and peanut skin extracts, GSE and
pine bark extract were found to have a remarkably similar qualitative profile
of PAC monomers and dimers. However, GSEs were generally found to contain
larger amounts of PACs than pine bark extracts. The chromatograms were submitted to cluster analysis, and
while GSEs were easily distinguished from peanut skin extracts, the lower
quality GSEs (i.e., those extracts containing lower concentrations of PACs)
clustered with the pine bark extracts.1 HPLC and HPLC-MS analyses were
used by Kelm et al. to differentiate authentic and commercially obtained GSEs. Atypical
peaks observed in HPLC profiles were further evaluated by HPLC-MS/MS, allowing the
investigators to characterize structures that are un-characteristic of the PACs
found in grape seeds; therefore, this approach can be used to detect
adulteration.13
For other methods, such as testing for
peanut allergens, or genetic methods to detect peanut DNA, there are no
published data available that have verified their fitness for the purpose of
detecting GSE adulteration with peanut skin extracts.
3.7 Perspectives: Adulteration of GSE has been exposed only recently, but seems to be
widespread. According to GSE producers, many GSE products sold on the Chinese
market are adulterated (X. Jin e-mail to S. Gafner, October 2, 2015). Demand for
GSE is expected to continue to increase with more health benefits supported by human
clinical studies, increasing the demand in the extract, increasing the risk of
adulteration, and potentially eroding consumer confidence, safety, and efficacy
if adulterants are used.
4
Conclusions
Adulteration of GSE in commercial products appears to be
a significant problem. Villani et al., determined that out of the 21 commercial
products, six samples contained no detectable quantities of GSE, and were composed
primarily of peanut skin extract as determined by comparison to authentic
peanut skin.1 Adulteration with peanut skin extract represents a
significant safety concern due to the possibility of reactions to peanut allergens.
In addition, peanut skins are much less expensive than GSE and sale of
adulterated lower-cost material has a significant economic impact. Companies
producing authentic GSE cannot compete with adulterated products and lose sales
due to consumers making a price-oriented purchasing decision. More importantly,
those manufacturers that unknowingly buy adulterated products and perform
analytical tests that are easily fooled are being defrauded and at risk of
regulatory actions due to their GSE products being non-compliant with current
Good Manufacturing Practice (cGMP) requirements.
One of the primary reasons
that adulteration goes undetected is due to manufacturers relying on unspecific
spectrophotometric methods for quality control of their materials. While
spectrophotometric assays can provide reliable results for the contents in
total phenolics, HPTLC and HPLC-UV/MS are more appropriate for the purpose of GSE
identification
†The acronym GSE should not be confused with acronym GFSE,
referring to Grapefruit Seed Extract, which is an entirely different material.
In some original publications on GFSE adulteration, the authors use “GSE” to
refer to grapefruit seed extract.
5 References - Villani
TS, Reichert W, Ferruzzi MG, Pasinetti GM, Simon JE, Wu Q. Chemical investigation of commercial
grape seed derived products to assess quality and detect adulteration. Food
Chem. 2015;170:271-280.
- McGuffin M, Kartesz JT, Leung AY, Tucker AO. American Herbal Products Association’s Herbs
of Commerce. 2nd ed. Silver Spring, MD:
American Herbal Products Association; 2000.
- The
Plant List. Version 1.1 (September 2013). Available at: http://www.plantlist.org.
Accessed August 18, 2015.
- Tropicos.org. Missouri Botanical Garden.
Available at: http://www.tropicos.org. Accessed August 18, 2015.
- Cavaliere
C, Rea P, Blumenthal M. Herbal supplement sales in United States show growth in
all channels. HerbalGram. 2010;78:60-63.
Available at: http://cms.herbalgram.org/herbalgram/issue78/article3263.html.
Accessed October 1, 2015.
- Cavaliere
C, Rea P, Lynch ME, Blumenthal M. Herbal supplement sales experience slight
increase in 2008. HerbalGram.
2009;82:58-61. Available at: http://cms.herbalgram.org/herbalgram/issue82/article3400.html.
Accessed October 1, 2015.
- Cavaliere C,
Rea P, Lynch ME, Blumenthal M. Herbal supplement sales rise in all channels in
2009. HerbalGram. 2010;86:62-65.
Available at: http://cms.herbalgram.org/herbalgram/issue86/article3530.html. Accessed October 1, 2015.
- Blumenthal M,
Lindstrom A, Lynch ME, Rea P. Herbs sales continue growth – up 3.3% in 2010. HerbalGram.
2011;90:64-67. Available at: http://cms.herbalgram.org/herbalgram/issue90/MarketReport.html. Accessed October 1, 2015.
- Blumenthal M,
Lindstrom A, Ooyen C, Lynch ME. Herb supplement sales increase 4.5% in 2011. HerbalGram. 2012;95:60-64. Available at:
http://cms.herbalgram.org/herbalgram/issue95/hg95-mktrpt.html. Accessed October 1, 2015.
- Dry Creek Nutrition, Inc. Acquires ActiVin(TM) Grape Seed Extract; Grape
Seed Extract Positioned as Next Powerful Antioxidant to Grow Nutraceutical
Category [press release].
Modano, CA: PRNewswire; April 10, 2001. Available at: http://www.prnewswire.com/news-releases/dry-creek-nutrition-inc-acquires-activintm-grape-seed-extract-grape-seed-extract-positioned-as-next-powerful-antioxidant-to-grow-nutraceutical-category-82362632.html. Accessed April 21, 2016.
- Polyphenols
Forecast 2013-2014. Engredea/Nutrition Business Journal monograph. Boulder, CO:
New Hope Media. 2013:13.
- Sun C, McIntyre
K, Saleem A, Haddad PS, Arnason JT. The relationship
between antiglycation activity and procyanidin and phenolic content in
commercial grape seed products. Can
J Physiol Pharmacol. 2012;90(2):167-174.
- Kelm MA, Kupina
S, Shrikhande A. Grape seed extract authentication. Oral presentation AGFD 22,
250th American Chemical Society National Meeting & Exposition,
Boston, MA, August, 2015.
- Gu L, Kelm MA, Hammerstone JF, et al. Concentrations of proanthocyanidins in
common foods and estimations of normal consumption. J Nutr. 2004;134(3):613-617.
- Olschläger C, Regos
I, Zeller FJ, Treutter D. Identification of galloylated propelargonidins and
procyanidins in buckwheat grain and quantification of rutin and flavanols from
homostylous hybrids originating from F.
esculentum x F. homotropicum. Phytochemistry. 2008;69(6):1389-1397.
- Hellström JK, Törrönen AR, Mattila PH. Proanthocyanidins in common food
products of plant origin. J Agric Food
Chem. 2009;57(17):7899–7906.
- Li HJ, Deinzer ML. Structural identification and
distribution of proanthocyanidins in 13 different hops. J Agric Food Chem. 2006;54(11):4048-4056.
- Kalili KM, de Villiers A. Off-line comprehensive
two-dimensional hydrophilic interaction x reversed phase liquid chromatographic
analysis of green tea phenolics. J Sep
Sci. 2010;33(6-7):853-63.
- Sudberg É,
Sudberg S, Nguyen J. Validation of a high performance thin-layer chromatographic
fingerprint method for the simultaneous identification of grape seed and peanut
skin and the adulteration of commercial grape seed extract with peanut skin.
AHPA (American Herbal Products Association) Botanical Congress, Las Vegas, NV.
October 10, 2014.
- Pais P. Botanical extract adulteration in the US market. Presented at: SupplySide West; November
2012; Las Vegas, NV.
- Reed KA.
Identification of phenolic compounds from peanut skin using HPLC-MSn.
PhD thesis. Blacksburg, VA: Virginia Polytechnic Institute and State
University; 2009. Available at: http://scholar.lib.vt.edu/theses/available/etd-12182009-214904/unrestricted/Reed_KA_D_2009.pdf. Accessed January 26, 2016.
- Constanza KE,
White BL, Davis JP, Sanders TH, Dean LL. Value-added processing of peanut
skins: antioxidant capacity, total phenolics, and procyanidin content of
spray-dried extracts. J Agric Food Chem. 2012;60(43):10776-10783.
- Nordlee JA,
Taylor SL, Jones RT, Yunginger JW. Allergenicity of various peanut products as
determined by RAST inhibition. J Allergy Clin Immunol.
1981;68(5):376-382.
- Sicherer SH,
Muñoz-Furlong A, Godbold JH, Sampson HA. US prevalence of self-reported peanut,
tree nut, and sesame allergy: 11-year follow-up. J Allerg Clin Immunol.
2010;125(6):1322-1326.
- University of
Portsmouth; Literature searches and reviews related to the prevalence of food
allergy in Europe. EFSA supporting publication 2013:EN-506. Available at: http://www.efsa.europa.eu/sites/default/files/scientific_output/files/main_documents/506e.pdf.
Accessed April 21, 2016.
Revision Summary
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