Adulteration of Rhodiola (Rhodiola rosea) Rhizome, Root, and Extracts

By Ezra Bejar, PhD,Roy Upton,b and John H. Cardellina II, PhDc

American Botanical Council, PO Box 144345, Austin, TX 78714
American Herbal Pharmacopoeia, PO Box 66809, Scotts Valley, CA 95067,
cReevesGroup, 1137 Treefern Drive, Virginia Beach, VA 23451*Corresponding author

Keywords: Rhodiola rosea, rhodiola, rhodiola root, rhodiola root extract, arctic root, arctic rose, golden root, adulterant, adulteration, substitution, Rhodiola crenulata, Crassulaceae

 

Goal: The goal of this bulletin is to provide timely information and/or updates on issues of adulteration, substitution, potential interchangeable use, and mislabeling of Rhodiola rosea rhizome/root, in particular with other species from the genus Rhodiola, e.g., R. crenulata. The bulletin may serve as guidance for quality control personnel, the international herbal products industry, regulators, and extended natural products community in general. It is also intended to summarize the scientific data and analytical methods on the occurrence of species substitution and/or adulteration, the market situation, and economic and safety consequences for the consumer and the industry.

1          General Information 

1.1 Common name for Rhodiola rosea: Rhodiola1

The American Herbal Products Association’s Herbs of Commerce, 2nd edition1 also applies the Standardized Common Name “rhodiola” to R. algida and R. kirilowii. (see section 1.10)

 

1.2 Other common names:

English: Arctic rose, king’s crown, roseroot, Arctic root, rosewort, snowdown rose, Tibeten rhodiola root1-4

Chinese: Hong jing tian (红景天)1,3,5-8

Danish: Rosenrod

Dutch: Rozewortel

French: Orpin rose, rhodiole, racine arctique, racine d’or

German: Rosenwurz

Italian: Rhodiola, rodiola, radice d’oro, radice ártica

Japanese: Iwa-benkei (イワベンケ)

Mongolian: Yagaan mugez, altan gagnuur9

Norwegian: Rosenrot

RussianRodióla rózovaya (Родиола розовая), zolotoy koren (золотой корень – golden root)

Spanish: Raíz dorada Siberiana, raíz del Ártico, rizoma de Rhodiola

Swedish: Rosenrot

1.3 Accepted Latin binomial: Rhodiola rosea L. 10

 

1.4 Synonyms: Sedum rhodiola DC., Sedum rosea (L.) Scop., Sedum roseum (L.) Scop. 10

1.5 Common names for Rhodiola crenulata:

 

English: Bigflower rhodiola root,11 Rhodiola crenulata1

 

Chinese: Da hua hong jing tian (大花红景天)5-7

1.6 Botanical family: Crassulaceae

1.7 Distribution: Rhodiola rosea is native to boreal areas of Eastern Europe, China, and North America; its range extends from China to Russia, US Northern states, northern Canada, and Alaska. In New England it occurs along the Maine Coast and in southern Vermont. Disjunctive populations extend from the southern Appalachians to North Carolina. Taxonomic lumpers include the genus Rhodiola in a broader concept ofSedum, though most modern floras follow Linnaeus in segregating Rhodiola from Sedum. It is important to be aware that some references to Rhodiola rosea may treat the species as Sedum rosea or Sedum roseum.In the Arctic, plants typically occur in crevices or among patches of moss and other vegetation, often near shores. 9,10 The highest plant densities are found on grassy or rocky slopes on the weather side of coasts (in the north) or mountains (in the south). Depending on the latitude, the plants grow at altitudes from 800–3000 m (2625–9843 ft). In China, Rhodiola rosea grows in the northern to central provinces of Xinjiang, Gansu, Shanxi, Hebei, and Jilin.

Rhodiola crenulata (J.D. Hooker & Thomson) H Ohba is native to the high mountains and plateaus close to the Himalayas of China, Bhutan, Nepal, and the Indian province of Sikkim. In China, R. crenulata is found in the southwestern provinces of Xizang (Tibet), Qinghai, Sichuan, and Yunnan.12,13

1.8 Plant part and form: Rhodiola rosea raw material is sold in the United States in bulk, either in the form of dried rhizome, dried rhizome/root, or standardized extracts of dried rhizome or dried rhizome/root. According to the United States Pharmacopeia (USP), the raw plant material consists of the dried roots and rhizomes of R. rosea L. containing not less than (NLT) 0.3% of the phenylpropanoid glycosides rosarin, rosavin and rosin (these three compounds are also collectively referred to as ‘rosavins’) calculated as rosavin, and NLT 0.08% of salidroside, calculated on a dry weight basis.8 Hydro-alcoholic extracts of R. rosea roots and rhizomes should contain NLT 90.0% and not more than (NMT) 110.0% of the labeled amount of the above-mentioned phenylpropanoid glycosides (rosavins), and NLT 90.0% and NMT 110.0% of the labeled amount of salidroside.7 In Canada, R. rosea is sold as the dried root/rhizome, as an extract (standardized to contain 1-6% rosavins, or 0.8-3% salidroside), or as a tincture.14 Rhodiola rosea is sold in the EU as dried root/rhizome, an herbal tincture or dry extract, (drug:extract ratio 1.5-5:1, extraction solvent 67-70% ethanol, v/v).10

1.9 General use(s): Rhodiola rosea has a long history of use as a medicinal plant, appearing in the body of collected knowledge (materia medica) of many European countries15 and included in several traditional herbal systems in Asia and North America.5,6,14 Between 1748 and 1961, diverse medicinal applications for R. rosea have been reported in the scientific literature of Sweden, Norway, France, Germany, Iceland, and the Soviet Union, principally considered as an adaptogen, or an agent stabilizing physiological processes and promoting homeostasis, with various health-promoting effects.2,15 In Europe it is considered a traditional herbal medicinal product used for temporary relief of stress symptoms, such as fatigue and sensation of weakness.5,16 Uses in the European Union (EU), Australia, and New Zealand include support of cognitive function, such as mental focus and mental stamina, a source of antioxidants, and a source of immune function-enhancing constituents. In North America and Brazil, it is primarily used as an adaptogen, and to improve athletic performance by reducing recovery time after prolonged exercise. 2,14,17-19 In Central Asia, R. rosea was used traditionally as a remedy for the prevention and treatment of cold and flu.2 In Mongolia, R. rosea is traditionally used for fever, lung inflammation, and strengthening of the body, as well as a mouthwash for bad breath. 62

The genus Rhodiola has about 90 species possibly having originated in the mountainous regions of southwest China and the Himalayas. Altogether, over 20 species are used throughout Asia, in some cases interchangeably. Specific uses are given today in traditional Chinese medicine (TCM) to R. crenulata, R. kirilowii, R. quadrifida, R. sacra, and R. yunnanensis; the last four species have been often used as a substitute and even sold as R. crenulata in the Chinese markets.9 Rhodiola crenulata uses include tonification of qi, activation of blood circulation, and unblocking the meridians.11 Other species also mentioned as being used in TCM include R. atuntsuensis, R. algida, R. coccinea, R. himalensis, and R. subopposita. In Tibetan medicine, species such as R. alsia and R. chrysanthemifolia have also been used as a substitute to the more popular R. crenulata.9

According to traditional Chinese medicine expert Subhuti Dharmananda, PhD, of the Institute for Traditional Medicine in Portland, Oregon, the herb entered into some folk applications (local uses, not tied to the theoretical framework of TCM), but it was not an herb commonly recorded in standard Chinese materia medica. Hong jing tian is the Chinese denomination given to the root and rhizome of several Rhodiolaspecies. It is described as an adaptogenic herb that regulates physiological functions, and is believed to have a central stimulant action. Its general tonic actions are similar to those of ginseng (Panax ginseng, Araliaceae) and root and rhizome of Eleutherococcus senticosus (Araliaceae). [email to S. Gafner, May 5, 2017]

1.10 Nomenclature considerations: In the United States, many rhodiola products in the marketplace bear the R. rosea binomial in the nutritional/supplement facts panel listing ingredients on the label. Due to this species-specific statement, any mixing, dilution, substitution, or replacement with other Rhodiolaspecies will lead to a product’s being considered misbranded. Regardless of the law, the interchangeable use of different species within the same genus may create some variations in chemical composition, which could affect quality, safety and efficacy.

The first edition of Herbs of Commerce (1992),20 formerly the basis for standard nomenclature for herbal dietary supplements in the United States and the official document for commercial nomenclature cited in the Code of Federal Regulations (CFR), does not include any Rhodiola species. The second edition of Herbs of Commerce (2000)1 includes R. algida, R. kirilowii, and R. rosea under the standardized common name “rhodiola”, which means these species should be labeled as “rhodiola” or with the correct scientific name. The roots and rhizomes of these species are also assigned the Chinese pinyin name hong jing tian. Rhodiola crenulata is listed separately with the standardized common name of “Rhodiola crenulata” and the Chinese pinyin name da hua hong jing tian. However, the CFR codification was not updated to include this second edition of Herbs of Commerce. In the Pharmacopoeia of the Peoples’ Republic of China (2010 Edition – Part I), the officially accepted species is Rhodiola crenulata and the medicinally used part is the dried root and rhizome. However, the Chinese pharmacopoeia lists hong jing tian rather than da hua hong jing tian as the common name of R. crenulata.

2          Market

2.1 Importance in the trade and market dynamics: The use of R. rosea as an ingredient in dietary supplements is quite extensive. According to the market research company SPINS, sales of R. rosea in the natural channel in the United States have been stable for four consecutive years from 2013-2016 (Table 1). Rhodiola rosea ranked #35 in 2013, and #36 in 2016, with sales in the range of US $2.2-2.5 million in the years 2013-2016. However, in the Mainstream Multi-outlet channel, R. rosea ranked #11 in 2013 with $17.7 million in sales, sliding to #28 in 2016 with $10.1 million in sales. The decrease in the Mainstream Multi-outlet channel is thought to be multifactorial.21

As noted above, the sales data for 2013-2016 (Table 1) indicate a gradual decrease in sales of R. rosea-based products in the United States. Retail pricing for the rhizome is in the range of US $30-100/kg dried rhizome, according to an informal Internet search conducted in September 2016. However, standardized R. rosea extract (3% rosavins/1% salidroside) is sold by suppliers to dietary supplement manufacturers in a price ranging from 80-110 €/kg in the EU and US $70-100/kg, depending on the extract quality. (A. Bily [Naturex] oral communication to E. Bejar, October 5, 2016)

Table 1. Rhodiola Dietary Supplement Sales in the US from 2013-2016

Channel 2013 2014 2015 2016
Rank Sales [US$] Rank Sales [US$] Rank Sales [US$] Rank Sales [US$]
Naturala 35 2,214,255 32 2,561,873 35 2,461,235 36 2,588,730
Mainstream Multi-Outletb 11 17,716,775 17 14,188,978 27 10,624,592 28 10,080,448

aAccording to SPINS (SPINS does not track sales from Whole Foods Market.)
bAccording to SPINS/IRI (The Mainstream Multi-Outlet channel was formerly known as the Food, Drug, and Mass Market channel [FDM], exclusive of possible sales at Walmart, a major retailer in the US and beyond.)
Sources: Smith T, et al.22; T. Smith (American Botanical Council) e-mail to S. Gafner, September 2, 2015 and September 3, 2015. K. Kawa (SPINS) e-mail to S. Gafner, July 11, 2016.

2.2 Supply sources: The largest natural resources for R. rosea are in Russia. The major part of the growing range cannot be exploited due to difficulties in access or sparse populations. Most R. rosea raw material is collected in China by wildcrafters, whose subsistence depends on selling their fresh produce at regional collection sites. Most of the root plant material is gathered in the summertime from a minimum of four-year old plants by digging under the plant, removing most of the rhizome/root and (hopefully) leaving a part of the rhizome/root for the plant to regenerate over the next years. Rhodiola crenulata is often collected for the Chinese market in some regions in China and Mongolia where both species may share ecological niches. Wildcrafters should be able to distinguish R. rosea from R. crenulata easily during the collection season, since R. rosea has yellow flowers with yellow to reddish buds, while R. crenulata flowers are purple.12

The Xinjiang region is one of the most prolific producers of R. rosea with 4-5 collection sites selling about 500 tons of dry rhizomes annually. The dried roots/rhizomes are cleaned, dried, and sold to one of several East China extract manufacturers; most such extracts are sold abroad. Other regions of China, Mongolia, Kazakhstan, Russia, and North America have a more limited supply of R. rosea, and their contribution to the US market is small, except for a few select products. Most Mongolian and Kazakhstani R. rosea end up in the Russian market at a higher price. (A. Bily and C. Pierron [Naturex] oral communication to E. Bejar. September 29, 2016).

Projects for cultivation of R. rosea exist in Denmark, Germany, Canada, Alaska, Bulgaria, Switzerland, and Norway. Production in the latter two countries is small and limited to supply local and regional markets.

2.3 Raw material forms: Dried rhizome/root is sold in whole or powdered form, or after extraction with alcohol-water mixtures and subsequent spray-drying. The extract may contain suitable added substances as carriers. Various lots of extracts are often mixed to meet standardization requirements of the USP monographs.7,8

Because wildcrafters collect the rhizome (with root material) exclusively, and leave parts of the root with the aerial parts of the plant behind to regenerate, it is rare to find adulteration of R. rosea rhizome with aboveground plant parts. However, suppliers from China sell R. rosea aerial plant (herb), flowers, and stems according to their certificates of analysis. The sale of R. rosea herb and flower extracts, correctly labeled as such, is not within the scope of this bulletin.

3          Substitution

3.1 Known substitutes and adulterants: The main concern regarding the authenticity and quality of R. rosea is the admixture of, or substitution with, rhizome/root material from other Rhodiola species. Over 90 Rhodiola species have been documented in the world and in China 73 different Rhodiola species have been reported, mainly in the northwest and southwest regions, such as Tibet and the Sichuan province.19 ManyRhodiola species have similar pinyin names (hong jing tian)23 and are used interchangeably in China and other parts of Asia, including R. crenulata R. heterodontaR. kirilowiiR. quadrifida, and R. semenovii.1,15,19However, R. crenulata is the only species formally accepted in the PPRC.11 Because of the number of imports from Asia, mainly from China, to the United States and to the European herbal supplement industry, R. rosea raw materials are often mixed or interchanged with other Asian species, including R. crenulata, but also other Rhodiola species.19,23 Adulteration with materials other than those from the Rhodiola genus, e.g., with 5-hydroxytryptophan, has been described by Booker et al.,19 but seems to be infrequent.

Herbal medicine experts have expressed contrasting views about the interchangeable use of R. rosea and other Rhodiola species in standard-setting documents and reference textbooks. The European Medicines Agency’s community herbal monograph specifies the use of R. rosea for rhodiola-containing products that are marketed as an herbal drug for temporary relief of symptoms of stress.4,5  Similarly, the highly regarded German textbook Wichtl – Teedrogen und Phytopharmaka24 indicates that rhizomes from other Rhodiola species may appear as adulterants of R. rosea. However, the USP Herbal Medicines Compendiumlists R. crenulata, R. kirilowii, R. sacra, R. sachalinensis, and R. yunnanensis, as confounding materials for R. rosea rhizome.8 This is a more accurate way to characterize the substitution or admixing of related species within a genus. In the United States, by regulatory definition, replacement by, or admixing with a species that is listed under the same common name in the American Herbal Products Association’s Herbs of Commerce, 1st edition,20 is considered substitution, unless the product label notes a particular species in the ”active ingredients” section. Hence, products labeled to contain “rhodiola”, but not specifying a particular species of Rhodiola, may be derived from a number of Rhodiola species (see section 1.1).

3.2 Sources of information supporting substitution of rhodiola and frequency of occurrence: With the use of a rapid resolution liquid chromatography (RRLC, a variation of high-performance liquid chromatography [HPLC]) method, Ma et al. found that approximately one-third of the commercial rhodiola rhizome powder extract samples they tested did not show a consistent RRLC profile and lacked the characteristic peaks of rosarin, rosavin, and rosin present in authentic R. rosea rhizome.25 However, absence of rosavins may not always be indicative of adulteration. If not handled properly, rosavins may be subject to enzymatic degradation and thus not be present in a finished product (Y-C Ma email to S. Gafner, May 26, 2017).

Booker et al. analyzed 39 raw materials of products from different vendors in the United Kingdom (UK) labeled as R. rosea. Most products were sold without any registration (i.e., generally unlicensed food supplements available on the internet or from retail outlets), although the researchers included two Traditional Herbal Medicine products registered under the traditional herbal medicine products directive (THMPD).19 Registration of a product under the THMPD requires the submission of appropriate data supporting the safety of the product (qualitative and quantitative composition, manufacturing process and controls, potential risks to the environment, therapeutic benefits and dosage, contraindications and known adverse reactions, pharmacovigilance data, and packaging information), but does not include the need for preclinical or clinical data. Products were compared to R. rosea crude drug reference material and two bulk powders. The samples were analyzed by 1H-NMR (nuclear magnetic resonance) spectroscopy and high-performance thin-layer chromatography (HPTLC). Results from 1H-NMR were evaluated statistically using principal component analysis (PCA). Rhodiola rosea products registered under the THMPD were confirmed to contain authentic R. rosea, but seven (about 25%) unregistered food supplements labeled as R. roseaproducts were determined to be substituted with various other Rhodiola species, and in one instance adulterated with synthetic 5-hydroxytryptophan (5-HTP). The PCA model used to analyze 1H NMR spectroscopy data appeared to discriminate poorly between dietary supplement products containing R. rosea extracts and those extracts containing R. crenulata or other Rhodiola species when using the entire NMR spectrum, likely due to the presence of excipients. Restricting the 1H NMR spectrum to the aromatic region allowed the distinction among R. rosea and various other Rhodiola species. The HPTLC method detected both admixed/substituted and adulterated samples effectively.19

Several analyses of crude samples of R. crenulata rhizome confirmed that the rhizome does not contain rosavin, but does contain salidroside and other p-tyrosol derivatives, a class of compounds also found in R. rosea.15,26 Salidroside is associated with increase of exercise tolerance.27 Another Rhodiola species, R sachalinensis, was found to contain both rosavin and salidroside, but at lower concentrations than R. rosea;23,29 contrarily, a TLC analysis by Kurkin et al.28 did not find any rosavins in R. sachalinensis.23,29Booker et al. verified the identity of 45 commercial samples (labeled to contain R. rosea [N = 11], R. crenulata [N = 7], R. sachalinensis [N = 4], R. quadrifida [N = 3] or Rhodiola spp. [N = 20]), collected from retailers, local markets, and the internet in China and the United Kingdom, by HPTLC and 1H NMR with subsequent statistical analysis. An analysis of the 11 samples labeled to contain R. rosea indicated that eight (72.7%) contained other Rhodiola species, with four samples containing R. crenulata and one R. serrata23,29 Three of the seven purported R. crenulata samples were also composed of the incorrect species, containing either R. serrata (N = 2) or an unknown material (N = 1).

An unpublished investigation from 2008 by researchers of the University of Ottawa and the Montreal Botanical Garden of the quality of 20 commercial products sold as tablets, capsules, or liquid extracts on the North American market found salidroside (14.4-45.7 mg/g of product) and rosavins (6.1-68.5 mg/g of product) to be present in every sample. The data, obtained using HPLC-UV, suggest that these products contained authentic R. rosea rhizome and root (A. Cuerrier [Montreal Botanical Garden] email to S. Gafner, November 8, 2016).

3.3 Accidental vs intentional substitution: Both intentional and accidental Rhodiola substitution seems to occur during collection based on anecdotal (A. Bily and C.Pierron [Naturex], oral communication to E. Bejar, September 29, 2016) and scientific evidence. 23,29,30 This has been confirmed in a systematic field collection study, which identified several factors contributing to a substitution of Rhodiola species: (1) the lack of genuine raw material, (2) confusion over the (vernacular) Chinese pinyin name of the plant when sourcing from China, and, (3) deliberate substitution during the (collection and) manufacturing of a dietary supplement. 23 In the Altai region, an area in southern Siberia in Russia, there are 24 different species of the genus Rhodiola that could be misclassified as R. rosea by collectors.15

Resource depletion and habitat destruction have led to the disappearance of Rhodiola species in many locations, as most raw materials are wildcrafted and the plant needs several years to regenerate. In some geographical areas, the two most frequently used species, R. crenulata and R. rosea, are becoming vulnerable or at-risk (one source uses the terms “threatened” and “critically endangered” when referring to specific areas),31 making them more expensive to obtain. 23,30,31

Lack of proper collection procedures and the possible interchangeability of Rhodiola species may also contribute to R. rosea and/or R. crenulata being frequently substituted by or accidentally substituted with other Rhodiola species. The fact that most Rhodiola species (in particular, R. rosea and R. crenulata) are morphologically distinct suggests that the lack of raw material definitions and collection guidelines leads collectors to pick or substitute with whatever Rhodiola is locally available. After removal of the aboveground parts, the similarity in the root/rhizome morphology makes it practically impossible to distinguish one species macroscopically from the other and separate them before processing, although they can be distinguished chemically.

Different Rhodiola species, including R. rosea and R. crenulata, can be found on the Chinese market. Often, these are neither sold separately nor well-identified; therefore, there is a high potential of substitution and admixing among these species. While R. crenulata root/rhizome is preferred over R. rosea in TCM, this species is sometimes substituted with R. rosea, R. serrata, or other Rhodiola species. 23,30

The prevalence of R. crenulata on the Chinese market is most likely due to its greater abundance; it is not considered to be a substitute or an adulterant for R. rosea. Overall, the Chinese market is driven by Chinese names, not Latin names, and the Chinese name hong jing tian as an umbrella term generally refers to multiple species of Rhodiola, of which R. crenulata is the most abundant in trade. In China, it is rare for vendors to differentiate the various species, and most vendors have little knowledge about rhodiola because it has a short history of use in TCM and trade. They sell it because it is popular as a general health food item but most vendors know little about it beyond its province of origin, which does not always correlate to the species or morphological form.

As certain Rhodiola species, e.g., R. rosea and R. crenulata, are becoming scarce in the field, other Rhodiola species such as R. fastigiata, R. quadrifida, R. sacra, and R. serrata appear to be replacing them in the market. 32 For example, in a recent analysis of raw material samples purchased from drug stores and hospitals in China, only 40% of the samples labeled to contain R. crenulata were conclusively identified as such, while 40% were replaced with R. serrata, and the remaining samples with other Rhodiola species. 32As demand for the rhizome of R. rosea and R. crenulata increases, so does the cost, creating a greater risk that species substitution will occur.

Although substitution of R. rosea products with R. crenulata is considered the main problem with respect to authenticity of R. rosea species, 19,29 field work data suggest that other species are being implicated. A particular case is R. sachalinensis, a species that has a similar composition to R. rosea, containing rosavins (the marker compounds used to identify R. rosea), as well as salidroside, and is considered by some botanists to be the same species as R. rosea.23,32,33 To complicate matters, different populations of R. sachalinensis may display differences in their high-performance liquid chromatography-ultraviolet detection (HPLC-UV) fingerprints, making accurate species identification based on chemical analysis difficult.32However, substitution with R. sachalinensis may become less of a concern, since its growing range has decreased significantly and it is now considered to be critically endangered in China.Conversely, as the various species of Rhodiola are used interchangeably within traditional systems, differentiation may be necessary only when claiming to sell a specific species.

3.4 Possible safety issues: According to an assessment report by the European Medicines Agency and a more recent safety review, ingestion of R. rosea is considered safe.4,34 Although no assessments of R. crenulata or other Rhodiola species that might be used as substitutes have been published, there are no apparent health concerns when R. rosea is substituted with other materials from the same genus. There is a report about herb-drug interactions based on the fact that Rhodiola species rhizomes contain various amounts of salidroside. Salidroside has been found to significantly inhibit CYP3A4, which is an important drug-metabolizing enzyme. Although the potential for this interaction is based mostly on in vitro data, one clinical case report suggests this could be of clinical relevance leading to amplification of the effects of drugs with CYP3A4 mediated metabolism.34

3.5 Analytical methods to detect substitution: Roots and rhizomes of R. rosea can be distinguished from roots/rhizomes of R. crenulata and other Rhodiola species by trained experts using botanical, TLC, HPLC, NMR, and genetic methods. The color of the flower allows distinguishing R. rosea from R. crenulataand other purple-flowering species botanically.8,9,12,35 Dried rhizomes of various Rhodiola species, however, cannot be differentiated macroscopically from one another, but can be distinguished by chemical comparisons to authentic reference materials.

One of the approaches to distinguish R. rosea rhizome from other Rhodiola species is the presence/absence of rosavins by TLC. The first TLC method to detect rosavins was reported by Kurkin et al.28 Several other methods have been developed since then, including an HPTLC method with very clear criteria to distinguish R. rosea from other Rhodiola species.23,36,37

Kurkin et al. noted that salidroside was common in the genus Rhodiola, but among 11 Rhodiola species that were tested, only R. rosea contained the rosavins, allowing one to use the presence or absence of these compounds to possibly differentiate among species.28 The lack of rosavins in R. sachalinensis was later refuted by other researchers.23,29 Various HPLC methods have been reported in the literature to distinguish R. rosea chemically from other species. 38-40 The use of rosarin, rosavin, and rosin as marker compounds is critical to ensure identity of R. rosea products. Identification of R. rosea products containing other Rhodiola species may require not only identification of the presence of the rosavins, but also quantification of the amount of each and their ratios. Other methods have been suggested, including NMR-based metabolomics, 23,41 and HPTLC. The suite of methods appears to be helpful in detecting irregularities in commercial R. rosea products.

A DNA barcoding approach to identify Rhodiola species, based on 189 accessions representing 48 of the 55 species of Rhodiola described in the Flora of China,7 has been reported.42 The results suggested that the internal transcribed spacer (ITS) genomic region was best suited for use as a single-locus barcode, resolving 66% of the Rhodiola species. Combining five loci (rbcLmatKtrnH-psbAtrnLF, and ITS) increased the resolution to 81% of the species. However, the DNA method may not be considered adequate when used alone in quality control procedures, since close to 20% of species cannot be distinguished, and also due to the inability to discern the plant part. Various DNA-based approaches have also shown little success in species identification of highly processed botanical ingredients, e.g., extracts.

4          Conclusions

Substitution or mixing of R. rosea root/rhizome raw material and extracts with other species, especially R. crenulata, remains an issue of regulatory concern for manufacturers and marketers of products labeled as R. rosea. Substitution of R. rosea with other Rhodiola species can be detected botanically and through chemical analysis (e.g., HPTLC, HPLC and NMR). The increasing scarcity of wildcrafted R. rosea and R. crenulata, as well as reliance on complex supply chains involving many stakeholders (especially many collectors in diverse regions, particularly in China), is increasing the likelihood for substitution and admixing with other Rhodiola species, particularly R. fastigiata, R. quadrifida, R. sacra, and R. serrata.

5                 References

  1. 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.
  2. Brown R, Gerbarg P, Ramazanov Z. Rhodiola rosea – a phytomedicinal overview. HerbalGram. 2002;56:40-52.
  3. Moran RV. Rhodiola rosea. Flora of North America. Vol 8. New York, NY and Oxford, United Kingdom: Flora of North America North of Mexico. 20+ vols.; 1993-2017:167.
  4. Assessment report on Rhodiola rosea L., rhizoma et radix London, United Kingdom: European Medicines Agency Committee on Herbal Medicinal Products (HMPC); 2011:1-32.
  5. Community herbal monograph on Rhodiola rosea L., rhizoma et radix. London, United Kingdom: European Medicines Agency Committee on Herbal Medicinal Products (HMPC); 2012:1-5.
  6. Rhodiola quadrifida Fisch & Mey and Rhodiola rosea L. Medicinal Plants in Mongolia. Geneva, Switzerland: World Health Organization (WHO); 2013:163-172.
  7. Powdered Rhodiola rosea extract. USP 40 – NF 35. Rockville, MD: United States Pharmacopeial Convention; 2017:6809-6810.
  8. Rhodiola roseaUSP 40 – NF 35. Rockville, MD: United States Pharmacopeial Convention; 2017:6805-6807.
  9. Cuerrier A, Tendland Y, Rapinski M. Ethnobotany and conservation of Rhodiola species. In: Cuerrier A, Ampong-Nyarko K, eds. Rhodiola rosea. Boca Raton, FL: CRC Press; 2014.
  10. Rhodiola rosea. Germplasm Resources Information Network [Internet]. United States Department of Agriculture, Agricultural Research Service; 1998. Available at: https://npgsweb.ars-grin.gov/gringlobal/taxonomydetail.aspx?31156. Accessed May 24, 2017.
  11. Rhodiola crenulataPharmacopoeia of the Peoples Republic of China. Vol 1. Beijing, China: China Medical Science; 2010:376-377.
  12. Rhodiola. In: Wu Y-Z, Raven PH, eds. Flora of China. Vol 8. Beijing, China and St. Louis, MO: Missouri Botanical Garden Press; 2001:251-268.
  13. Bohm BA. The Geography of Phytochemical Races. Dordrecht, Netherlands: Springer Netherlands; 2009.
  14. Rhodiola – Rhodiola rosea. Ottawa, ON, Canada: Natural Health Products Directorate, Health Canada; 2013.
  15. Panossian A, Wikman G, Sarris J. Rosenroot (Rhodiola rosea): traditional use, chemical composition, pharmacology and clinical efficacy. Phytomedicine. 2010;17(7):481-493.
  16. Hartwich M. The importance of immunological studies on Rhodiola rosea in the new effective and safe herbal drug discovery. Centr Eur J Immunol. 2011;35(4).
  17. Rhodiola rosea. Therapeutic Research Faculty; 2007.
  18. Anonymous. Rhodiola rosea. Monograph. Altern Med Rev. 2002;7(5):421-423.
  19. Booker A, Jalil B, Frommenwiler D, et al. The authenticity and quality of Rhodiola rosea products. Phytomedicine. 2016;23(7):754-762.
  20. Moley T, Foster S, Awang D, Hu SY, Kartesz JT, Tucker AO. Herbs of Commerce. 1st ed. Austin, TX: American Herbal Products Association; 1992.
  21. Smith T, Kawa K, Eckl V, Johnson J. Sales of herbal dietary supplement sales in US increased 7.5% in 2015. HerbalGram. 2016;111:67-73.
  22. Smith T, Kawa K, Eckl V. Herbal supplement sales in US increase 7.7% in 2016. HerbalGram. 2017;115:56-65.
  23. Booker A, Zhai L, Gkouva C, Li S, Heinrich M. From traditional resource to global commodities: a comparison of Rhodiola species using NMR spectroscopy-metabolomics and HPTLC. Front Pharmacol. 2016;7:254.
  24. Lichius JJ, Loew D. Rhodiola rhizoma et radix. In: Blaschek W, ed. Wichtl – Teedrogen und Phytopharmaka. 6th ed. Stuttgart, Germany: Wissenschaftliche Verlagsgesellschaft mbH; 2016:554-555.
  25. Ma Y-C, Wang X-Q, Hou F, et al. Rapid resolution liquid chromatography (RRLC) analysis for quality control of Rhodiola rosea roots and commercial standardized products. Nat Prod Commun. 2011;6(5):645-650.
  26. Ma C-Y, Tang J, Wang H-X, Gu X-H, Tao G-J. Simultaneous determination of six active compounds in Rhodiola L. by RP-LC. Chromatographia. 2008;67(5):383-388.
  27. Xu J, Li Y. Effects of salidroside on exhaustive exercise-induced oxidative stress in rats. Mol Med Rep.6(5):1195-1198.
  28. Kurkin VA, Zapesochnaya GG, Shchavlinskii AN, Nukhimovskii EL, Vandyshev VV. Method of analysis of identity and quality of Rhodiola rosea rhizome. Khim Farm Zh. 1985;19(3):185-190.
  29. Booker AJ, Zhai L, Heinrich M. A metabolomic and phytochemical based study of Rhodiola species sourced from Asia and Europe. Planta Med. 2015;81(16):SL3A_03.
  30. Xin T, Li X, Yao H, et al. Survey of commercial Rhodiola products revealed species diversity and potential safety issues. Sci Rep. 2015;5:8337.
  31. Allen D, Bilz M, Leaman DJ, Miller RM, Timoshyna A, Window J. European Red List of Medicinal Plants.Luxembourg, Luxemburg: Publications Office of the European Union; 2014.
  32. Zhao W, Shi X, Li J, Guo W, Liu C, Chen X. Genetic, epigenetic, and HPLC fingerprint differentiation between natural and ex situ populations of Rhodiola sachalinensis from Changbai Mountain, China. PLoS One. 2014;9(11):e112869.
  33. The Plant List. Version 1.1 Available at: http://www.theplantlist.org. Accessed May 19, 2017.
  34. Semple H, Bugiak B. Toxicology and safety of Rhodiola rosea. In: Cuerrier A, Ampong-Nyarko K, eds. Rhodiola rosea. Boca Raton, FL: CRC Press; 2014.
  35. Compositional guideline: Rhodiola rosea dried root (powdered) extract. In: Aging DoHa, ed. Symonston, ACT, Australia: Therapeutic Goods Administration; 2012:1-3.
  36. Rumalla C, Avula B, Ali Z, et al. Quantitative HPTLC analysis of phenylpropanoids in Rhodiola species. J Plan Chromatogr – Modern TLC. 2011;24(2):116-120.
  37. Rhodiola rosea root (Rhodiola rosea). HPTLC Association. Available at: http://www.hptlc-association.org. Accessed May 24, 2017.
  38. Ganzera M, Yayla Y, Khan IA. Analysis of the marker compounds of Rhodiola rosea L. (golden root) by reversed phase high performance liquid chromatography. Chem Pharm Bull 2001;49(4):465-467.
  39. Wang Q, Ruan X, Jin Z-h, Yan Q-c, Tu S-j. Identification of Rhodiola species by using RP-HPLC. J Zhejiang Univ Sci B. 2005;6(6):477-482.
  40. Avula B, Wang Y-H, Ali Z, et al. RP-HPLC determination of phenylalkanoids and monoterpenoids in Rhodiola rosea and identification by LC-ESI-TOF. Biomed Chromatogr 2009;23(8):865-872.
  41. Ndjoko Ioset K, Nyberg NT, Van Diermen D, et al. Metabolic profiling of Rhodiola rosea rhizomes by (1)H NMR spectroscopy. Phytochem Anal. 2011;22(2):158-165.
  42. Zhang JQ, Meng SY, Wen J, Rao GY. DNA barcoding of Rhodiola (Crassulaceae): a case study on a group of recently diversified medicinal plants from the Qinghai-Tibetan Plateau. PLoS One. 2015;10(3):e0119921.

Revision Summary

Version # , Author Date Revised Section Revised List of Changes
Version 1, E. Bejar, R. Upton, J.H. Cardellina II n/a n/a none
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Bulletin on Adulteration of Bilberry (Vaccinium myrtillus) Extracts

Goal:

The goal of this bulletin is to provide timely information and/or updates on issues of adulteration of bilberry extract to the international herbal industry and extended natural products community in general.

1 General Information

1.1 Common name: Bilberry3

1.2 Other common names:

English: European blueberry, whortleberry, huckleberry4

Chinese: Hei guo yue ju (黑果越桔)

French: Myrtille, ambroche, ambreselle, brimbelle, gueule-noire, raisin des bois, vigne des montagnes

German: Heidelbeere, Blaubeere, Schwarzbeere, Waldbeere, Bickbeere, Moosbeere

Italian: Mirtillo, ampulette, asaire, bagole, baggiole, cesarelle, giasine, lambrune, mirtillo nero, murucule

Spanish: Arándano azul, mirtilo

1.3 Accepted Latin binomial: Vaccinium myrtillus L.5,6

1.4 Synonyms: Vaccinium myrtillus var. oreophilum (Rydb.) Dorn, Vaccinium myrtillus subsp. oreophilum (Rydb.) Á. Löve, D. Löve & B.M. Kapoor, Vaccinium oreophilum Rydb.5

1.5 Botanical family: Ericaceae

1.6 Plant part and form: Bilberry extracts are made from fresh bilberry fruit.1 The extracts are often standardized to 25% anthocyanidins or 36% anthocyanins. Products that claim these levels of compounds may in actuality contain the same amount as the differences are most often due to different quantitative values obtained from using different analytical techniques. In the case of bilberry, high-performance liquid chromatography (HPLC) provides a lower quantitative value than ultraviolet-visible spectrophotometry (UV/Vis).7 Also found on the market are bilberry leaf extracts, or combinations of bilberry fruit and leaf extracts. Extracts made entirely from bilberry leaves and properly labeled as such are not within the scope of this document.

1.7 General use(s): The indications for bilberry fruit include the symptomatic treatment of dysmenorrhea associated with premenstrual syndrome, circulatory disorders in patients with capillary leakage or peripheral vascular insufficiency, and ophthalmic disorders.1,4,8 In addition, bilberry fruit is used topically for mild inflammations of the oral mucosa.4,8


2 Market

2.1 Importance in the trade: In the United States, bilberry was among the top 20 herbal supplements between 2007 and 2012 in the food, drug and mass market with annual sales above US $1.4 million in this channel.9-13 The market volume has been fairly steady in recent years (D. Stanek oral communication, January 23, 2015).

2.2 Supply sources: Commercial bilberries are sourced mainly from Scandinavian and Eastern European countries. The World Blueberry Acreage & Production report lists Poland as the major producer of bilberry, followed by Russia, Ukraine and Scandinavia. Commercial bilberry for the production of bilberry extracts is sourced mainly from Eastern European (Lithuania, Romania, Poland, Russia and Ukraine) and Scandinavian (Sweden, Finland, Norway) countries, but also from France, Italy, and the Netherlands. (D. Stanek oral communication, January 23, 2015; E. M. Martinelli e-mail, November 16, 2015)

2.3 Raw material forms: Bilberry extracts are prepared from fresh berries that are frozen and then extracted with aqueous ethanol or aqueous methanol, and further concentrated according to the manufacturer’s proprietary processes. Generally, the extract yield is approximately 100 times lower than the initial weight of raw material, i.e., 1 kg of fresh bilberry will provide ca. 10 grams of bilberry dry extract (D. Stanek oral communication, January 23, 2015). Dry extract materials using other manufacturing processes are also available.

2.4 Market dynamics: Tracking the bilberry harvest volume is difficult as the fruit is generally harvested by local people (i.e., wildcrafted) who then sell the fruit to brokers. A report from the North American Blueberry Council indicates that the total harvest for wild Vaccinium species (mostly bilberry, but other Vaccinium species, e.g., bog bilberry [V. uliginosum], are collected as well) in Europe was 11,340 metric tons (25 million lbs.) in 2008, 7,710 metric tons (17 million lbs.) in 2010, and 19,500 metric tons (43 million lbs.) in 2012.14

For 2012, the harvest in Poland was around 10,000 metric tons, but the harvest was mainly destined for the domestic market for confectionary and baked goods. Russia, Ukraine, and Scandinavia provided at least an additional 6,000 metric tons to the overall harvest.14 According to the report, the harvest in 2012 was particularly strong despite unfavorable weather conditions; since the economy was depressed in European countries, many people harvested wild blueberries for additional revenue.


3 Adulteration

3.1 Known adulterants: Materials that are used to adulterate bilberry extracts typically have an intensive dark blue color, such as anthocyanidin-containing extracts or red food coloring such as amaranth dye (FD&C Red 2, E 123). Anthocyanidin-rich extracts known to be used as substitute for bilberry include those from bog bilberry (Vaccinium uliginosum), lingonberry (V. vitis-idaea), blueberry species (V. angustifolium, V. corymbosum, V. floribundum), cranberry (V. oxycoccos and V. macrocarpon), raspberries (Rubus spp., Rosaceae), wild cherry (Prunus avium, Rosaceae), black chokeberry (Aronia melanocarpa, Rosaceae), European elder (Sambucus nigra, Adoxaceae) berry, black soybean (Glycine max, Fabaceae) hull, black rice (Oryza sativa, Poaceae), and mulberry species (Morus australis, M. nigra, Moraceae).2,15-18

The common names “blueberry” and “wild blueberry” have different meanings depending on the geographical location. In the US dietary supplement trade, the name “blueberry” is restricted to three species, Vaccinium angustifolium, V. corymbosum, and V. pallidum.3 In Europe, V. myrtillus is often called blueberry, though bilberry is the English word which refers to this species in the trade.3 The hybrid cultivated blueberries from which the majority of the commercial food supply is derived are generally called blueberries. North American wild blueberry, common blueberry, common lowbush blueberry, low sweet blueberry, and lowbush blueberry refer to V. angustifolium which grows in the Northeastern U.S. and is commercially harvested in its habitat. Velvet leaf blueberry (V. myrtilloides) is also traded as “wild blueberry,” and is mostly wild-harvested in the Canadian maritime provinces. It is safe to assume that “wild blueberry” in a commercial sense refers to both V. angustifolium and V. myrtilloides (Steven Foster, e-mail, July 1, 2015).

3.2 Sources of information confirming adulteration: There have been a number of publications on bilberry adulteration, such as the reviews by Foster and Blumenthal,2 Giacomelli et al.,16 Upton et al.,1 the presentation by Pace et al.,19 and the doctoral thesis by Primetta.20 Foster and Blumenthal distinguish between the deliberate adulteration of bilberry extracts by addition of extracts from anthocyanin-rich sources such as blueberry, cranberry, European elder, sweet cherry, and others, and the adulteration occurring in the markets in China, where extracts of lingonberry and bog bilberry are wild-harvested and offered as “homemade Chinese bilberry” and “Chinese domestic bilberry” extracts at prices as low as $10/kg.2 This is in contrast to the much more expensive authentic bilberry extract (see section 3.3 below). Two additional studies regarding adulteration of commercial bilberry extracts were published in 2013 and 2014.15,21 The investigation into the quality of 20 dietary supplements purchased in a store or over the Internet in Japan by ultra-high-performance liquid chromatography (UHPLC) with detection by visible light at 535 nm provided evidence for adulteration in one sample. The product in question was labeled to contain a mixture of bilberry and black currant (Ribes nigrum, Grossulariaceae) extracts, but instead consisted entirely of black currant.21 Gardana et al. analyzed 26 commercial bilberry materials including 14 bulk extracts, six food supplements, and six juices by UV/Vis spectrophotometry and by UHPLC using a photodiode array detector (DAD). The samples were purchased either directly from the supplier (bulk extracts), or from herbal shops and local markets in Italy. The authors found an admixture of black mulberry in five samples (two extracts, three food supplements), and substitution of bilberry with chokeberry in two extracts and with a material tentatively identified as blackberry (Rubus spp.) in one extract. One food supplement did not contain any anthocyanins at all. Five of the juices were consistent with products made from bilberry fruit, while one juice did not contain measurable amounts of anthocyanins.15

3.3 Accidental or intentional adulteration: The limited supply and high commodity prices of bilberry raw materials have created an incentive for economically-motivated adulteration. In 2015 authentic bilberry extracts sold for a price of US $600-800/kg extract (D. Stanek oral communication, January 23, 2015). More easily accessible anthocyanin-containing fruit species can be collected in larger amounts than bilberry in a comparatively short time since many of these are readily available from cultivated rather than more expensive wild sources. The fruit from these other species can be made into extracts at a significantly lower cost than bilberry and can be priced below bilberry market rates while producing a profit for the producer/seller.

3.4 Frequency of occurrence: There are very little data on the extent of adulteration of commercial bilberry extracts and dietary supplements. A presentation by Pace et al. suggested that “adulteration of bilberry is rampant”;19 Roberto Pace, PhD, Director of Quality Control at Indena S.p.A. (Milan, Italy), the world’s leading marketer of bilberry extract whose use has been confirmed in clinical trials, commented that “bilberry is one of the most economically adulterated ingredients of the health food market” (R. Pace oral communication, November 5, 2015). As noted above, one study included results of 20 commercial products purchased in Japan, with only 13 of the products labeled to contain bilberry. Of these 13 products, one was found to be entirely composed of black currant, while the remainder did contain authentic bilberry.21 Another study looked at bilberry extracts from different manufacturers and supplements purchased on local markets in Italy. The results indicated that six out of 14 extracts and four out of six supplements were adulterated.15 Lee analyzed 15 commercial bilberry supplements purchased in the states of Washington and Idaho in the United States. Five products contained authentic bilberry material, and two samples could not be evaluated because they were composed of a mixture of anthocyanin-containing fruits, including bilberry. The remaining eight products were found to be adulterated.18 Based on the limited published data available, it is not possible to come to any conclusions about the frequency of bilberry adulteration, but it is accurate to say that it is not uncommon.

3.5 Possible safety/therapeutic issues: Most of the known adulterants of bilberry have a long-standing history of safe use in food and therefore do not represent a safety concern. However, adulteration of bilberry extracts with amaranth dye is of possible safety concern. Amaranth dye has been prohibited for use by the US Food and Drug Administration (FDA) since 1976 due to concerns about carcinogenicity, which are mainly based on two controversial studies in rats.22,23 The use of amaranth dye is still permitted in Europe but is limited to 0.15 mg/kg per day.24 Most botanical adulterants are cultivated plants and might be potentially contaminated by pesticides, largely used in the growing of berries. Conversely, pesticides are not an issue with wild-harvested bilberry.

3.6 Analytical methods to detect adulteration: The most suitable way to authenticate bilberry extracts and detect adulteration is by chemical analysis based on the specific anthocyanin fingerprint using either high-performance thin layer chromatography (HPTLC) or high-performance liquid chromatography (HPLC) with ultraviolet/visible (UV/Vis) and/or mass spectrometric (MS) detection. The monograph of the United States Pharmacopeia (USP)26 recommends use of HPLC, while that of the American Herbal Pharmacopoeia (AHP)1 and European Pharmacopoeia (EP)27 utilize the UV/Vis method after adequate identification tests have been performedThe use of UV/Vis spectrophotometry alone will allow measurement of total anthocyanins in bilberry extracts, but is not specific enough as an identity test. It can be applied as a quantitative tool only after the identity of the raw material has been assured. A comprehensive evaluation of 39 publicly available methods for the authentication and detection of adulterants in bilberry extracts, the Bilberry Extract Laboratory Guidance Document, is available through the ABC-AHP-NCNPR Botanical Adulterants Program.25

3.7 Perspectives: Don Stanek, US Sales Director at Linnea Inc., a European producer of bilberry extract, commented that adulteration of bilberry extracts is likely to persist, since the authentic material is so expensive (oral communication, January 23, 2015). Furthermore, explains Giovanni Appendino, PhD, professor of pharmaceutical sciences at the University ofEastern Piedmont (Novara, Italy) and consultant to Indena, the leading producer of bilberry extract, the price of the berries is subjected to significant variations due to the effect of climate on the labor-intensive harvest (e-mail, July 20, 2015).


4 Conclusions:
The adulteration of bilberry extracts continues to afflict the natural products industry. Since the raw material is harvested in the wild, the control of the supply chain is more challenging and adequate testing of the incoming raw material is crucial. Test methods outlined, e.g., in the USP,26 the EP,27 or in the AHP1 are able to detect adulteration of bilberry extracts and should be in place in every quality control laboratory to prevent manufacturers of bilberry extract products from becoming victims of companies providing fraudulent ingredients.


5 References

  1. Upton R, Graff A, Petrone C, Swisher D. American Herbal Pharmacopoeia and Therapeutic Compendium: Bilberry Fruit. Vaccinium myrtillus L.: Standards of Analysis, Quality Control and Therapeutics. Scotts Valley, CA: American Herbal Pharmacopoeia; 2001.
  2. Foster S, Blumenthal. The adulteration of commercial bilberry extracts. HerbalGram. 2012;96:63-74. Available at: http://cms.herbalgram.org/herbalgram/issue96/hg96-feat-bilberry.html. Accessed February 14, 2015.
  3. 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.
  4. Blumenthal M, Goldberg A, Brinckmann J (eds). Herbal Medicine: Expanded Commission E Monographs. Austin, TX: American Botanical Council; Newton, MA: Integrative Medicine Communications; 2000:16-21.
  5. The Plant List. Version 1.1 (September 2013). Available at: http://www.theplantlist.org. Accessed February 24, 2015.
  6. Tropicos.org. Missouri Botanical Garden. Available at: http://www.tropicos.org. Accessed February 24, 2015.
  7. Artaria C, Pace R, Maramaldi G, Appendino G. Different brands of bilberry extract: A comparison of selected components. Nutrafoods. 2007;6:13-18.
  8. World Health Organization: WHO monographs on selected plants, Volume 4. Fructus Myrtilli. WHO Press 2009;210-225.
  9. Cavaliere C, Rea P, Blumenthal M. Herbal supplement sales in United States show growth in all channels.HerbalGram. 2008;78:60-63. Available at: http://cms.herbalgram.org/herbalgram/issue78/article3263.html. Accessed February 14, 2015.
  10. 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 February 14, 2015.
  11. 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 February 14, 2015.
  12. 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 February 14, 2015.
  13. 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 February 14, 2015.
  14. Brazelton C. 2012 World Blueberry Acreage and Production Report. North American Blueberry Council. 2013.
  15. Gardana C, Ciappellano S, Marinoni L, Fachechi C, Simonetti P. Bilberry adulteration: identification and chemical profiling of anthocyanins by different analytical methods. J Agric Food Chem. 2014;62(45):10998-11004.
  16. Giacomelli L, Appendino G, Franceschi F, Togni S, Pace R. Omne Ignotum pro Magnifico: characterization of commercial Bilberry extracts to fight adulteration. Eur Rev Med Pharmacol Sci. 2014;18(24):3948-3953.
  17. Filippini R, Piovan A, Caniato R. Substitution of Vaccinium myrtillus L. for Aronia melanocarpa (Michx.) Elliott in acommercial batch. Plant Biosyst. 2011;145(1):175-181.
  18. Lee J. Anthocyanin analyses of Vaccinium fruit dietary supplements. Food Sci Nutr. 2016. doi: 10.1002/fsn3.339.
  19. Pace R, Morazzoni P, Appendino G. Omne ignotum pro magnifico: Getting bilberry out of the adulteration swamp. Talk presented at: 9th Oxford International Conference on the Science of Botanicals; April 14, 2010; Oxford, MS.
  20. Primetta A. Phenolic compounds in the berries of the selected Vaccinium species – the potential for authenticity analyses. PhD thesis. Kuopio, Finland: University of Eastern Finland; 2014.
  21. Yamamoto M, Yamaura K, Ishiwatari M, et al. Degradation index for quality evaluation of commercial dietary supplements of bilberry extract. J Food Sci. 2013;78:S477–S483.
  22. Andrianova MM. Carcinogenous properties of red food pigments – amaranth, SX purple and 4R purple, Vop. Pitan. 1970;29:61-65.
  23. Baigusheva MM. Carcinogenic properties of the amaranth paste, Vop. Pitan. 1968:27:46-50.
  24. European Food Safety Authority. Scientific Opinion on the re-evaluation of Amaranth (E 123) as a food additive. EFSA Journal. 2010;8(7):1649.
  25. Gafner S. Bilberry Extract Adulteration Laboratory Guidance Document. ABC-AHP-NCNPR Botanical Adulterants Program, Austin, TX. 2015. http://cms.herbalgram.org/BAP/LGD/BilberryLabGuidanceDocument.html. Accessed August 25, 2015.
  26. United States Pharmacopeial Convention. Powdered Bilberry Extract. In: USP 37-NF 32. Rockville, MD: United States Pharmacopeial Convention. 2014.
  27. The European Directorate for the Quality of Medicines. European Pharmacopoeia (EP 7.5). Myrtilli fructus recentis extractum siccum raffinatum et normatum. Strasbourg, France: Council of Europe; 2012:1130-1132.