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Adulteration of Aloe Vera (Aloe vera) Leaf Ingredients
By Ezra Bejar, PhD
American Botanical Council, PO Box
144345, Austin,
TX 78714
Correspondence: email
Citation (JAMA style): Bejar E. Adulteration
of aloe vera (Aloe vera) leaf
ingredients. Botanical Adulterants
Prevention Bulletin. Austin, TX: ABC-AHP-NCNPR Botanical Adulterants
Prevention Program; 2019.
Keywords:
Aloe
vera, aloe vera, adulteration,
aloe vera gel, aloe vera fillet, aloe vera leaf dry juice, aloe vera inner leaf
juice, aloe vera whole leaf juice, aloe vera leaf, aloe vera mucilage, aloe vera
juice
Goal: The goal of this bulletin is to provide
timely information and/or updates on issues of adulteration and mislabeling of aloe
vera leaf juice ingredients that purport to meet the quality standard
established by the International Aloe Science Council (IASC), an international trade
association of aloe vera leaf juice ingredient producers and product
manufacturers based in the United States and founded in 1980, applicable for
use in dietary supplement, personal care, and cosmetic products. The bulletin may serve as guidance
for quality control personnel, the international herbal products industry, and
the extended natural products community in general. It is also intended to
present a summary of the scientific data and methods on the occurrence of
species substitution and adulteration, the market situation, and economic and
safety consequences for the consumer and the industry.
Definitions:
Aloe vera leaf: The aloe vera leaf in its entirety. It
can be used as the raw material for the manufacture of aloe vera leaf juice
ingredients.1
Aloe vera whole leaf: The use of the term ‘whole’ was
introduced to differentiate ingredients where the entire leaf is used as a
starting raw material to create aloe vera leaf juice (without the latex
component) from those that start with inner leaf as the raw material. However,
the use of this term has led to confusion since aloe vera whole leaf juice may
be mistaken for a material containing latex.
Aloe vera inner leaf: The inner leaf (the clear, central
parenchymatous tissues of the aloe leaf) that may be used as the raw material
for aloe vera inner leaf juices.1
Aloe vera leaf gel: In order to differentiate the inner
leaf gel-like starting material from finished products that are gels by virtue
of added jelling agents, the IASC defined aloe vera leaf gel as a liquid
product with or without added thickening agents.1,2 The World Health Organization (WHO)
defines aloe vera gel as the colorless mucilaginous gel obtained from the
parenchymatous cells in the fresh leaves of Aloe vera.3 This is also correct but is not generally found as
an ingredient in finished products unless present as pulp.
Aloe vera inner leaf juice: According to the IASC, aloe vera inner
leaf juice is manufactured by stripping off the outer leaf rind before further
processing.2 It may contain pulp or be pulp free.
When thickening agents are added, it may be called a gel.1 It may also have trace anthrones, which
— depending on the manufacturing steps — may be removed through further
processing. When dried, it is properly called aloe vera inner leaf dry juice
though common industry shorthand for this ingredient is 200x because 200 parts
of liquid inner leaf juice yields approximately one part dry juice.
Aloe vera leaf juice: According to the IASC, aloe vera leaf
juice is manufactured by first macerating the entire leaf, rind and all. The
bitter yellow anthrone-rich latex from the rind is removed by filtration, which
is often accomplished via absorption by activated charcoal.1 This process is known as decolorization
and is routinely done for finished ingredients that may be referred to as aloe
vera decolorized, charcoal filtered, purified, or filtered leaf juice. Common
industry shorthand for this ingredient when dried to a dry juice is 100x
because about 100 parts of aloe vera leaf juice yields approximately one part dry
juice.
The term juice
has also been used to refer to aloe latex (the WHO specifies aloe juice as the bitter yellow
exudate originating from the bundle sheath cells of the leaf) which when inspissated
(thickened) becomes the anthrone-rich laxative drug derived from some species
of Aloe.3
1 General
Information
1.1 Common names: Aloe vera, aloe, Barbados aloe, burn
plant, Curaçao aloe, lily of the desert, true aloe, medicinal aloe, West Indian
aloe.4-8
1.2
Other common names:
Afrikaans: Aalwyn9
Chinese: Luhui ye (蘆薈葉)
6-8
Danish: Laegealoe9
Dutch: Aalewee, aloe9
French: Aloès, aloe vera, aloès
vulgaire, aloès des Barbades6,9,10
German: Aloe, echte Aloe, Barbados
Aloe, Curaçao Aloe6,9-11
Italian: Aloe delle Barbados, aloe di
Curaçao, aloe mediterranea9
Japanese: Aroe (アロエ)9
Portuguese: Azebre vegetal, babosa, babosa-medicinal, erva-babosa, aloe dos Barbados6,9
Russian: Aлоэ (aloe), столетник (stoletnik)
Sanskrit: Ghrita kumara, kanyasara
(dried juice of leaf)7
Spanish: Acibar, aloe, penca sabila, sábila, sávila, zábila3,6,9,12
Swedish: Äkta aloe9
1.3
Accepted Latin binomial: Aloe vera (L.) Burm. f.
1.4 Synonyms
Aloe barbadensis Mill.6-8,12,13
Aloe vulgaris Lam.13
1.5
Botanical family: Xanthorrhoeaceae
(alternatively placed in Aloaceae and Asphodelaceae)3,6,8,13,14
1.6 Distribution: Aloe species are found in sub-Saharan
Africa, the Arabian Peninsula, on Madagascar, and some smaller islands off the
east coast of Africa. Aloe is a
diverse group of more than 600 species.8,9,13 Aloe vera is especially abundant in southern and eastern Africa,
and long thought to be a native there. From this area, it was subsequently
introduced into northern Africa and other parts of the world.3 In the United States it
grows in the southern states of Texas, Arizona, and Florida.6,8,14 In Mexico it is grown in
the Northeastern states of Tamaulipas, Durango, San Luis Potosi, and Zacatecas,
and also in Campeche and Yucatan.8,15 Aloe vera was also introduced and is cultivated in many tropical
and subtropical countries including Argentina, Belize, Bolivia, China,
Colombia, Ecuador, El Salvador, Guatemala, Honduras, India, the Dominican
Republic, North Africa, Saudi Arabia, Thailand, Yemen, and Venezuela.6,14 The plant grows in stony
outcrops and sandy plains, roadsides, and similar places, in full sun, from sea
level to 1,300 m (4,265 ft).6
1.7
Plant part and form: A
number of ingredients are made from aloe leaf, which include the two juices: aloe
vera inner leaf juice, and aloe vera leaf juice (generally decolorized). When
dried (freeze-drying is one technique), the dry juices have been commonly
called 200x and 100x aloe vera powders, respectively (see Definitions in the
introduction).
Aloe
for use as a laxative, defined by the USP monograph16 as the dried
latex of the leaves of A. vera—known in commerce as aloe vera, Curaçao aloe, or
Barbados aloe—or of A. ferox, or of hybrids of A. ferox
with A. africana
and A. spicata,
known in commerce as Cape aloe, is not within the scope of this document.
1.8
General use[s]: Aloe’s first known historic use dates
back almost 6,000 years. Its medicinal application was first documented on a
Mesopotamian clay tablet dating from 2100 BCE, and the Ebers Papyrus (ca. 1550
BCE), discovered in Egypt in 1873, listing at least 12 aloe-containing
preparations for treating internal and external ailments.14 Dioscorides, in De Materia Medica
(65 AD), listed 19 different uses and actions of aloe, including as a purgative
(for constipation) when drunk with water or milk, as a means to stop bleeding
hemorrhoids when used internally, and for the treatment of ulcers and wounds, skin
afflictions, and boils, when used externally.3,5,6,14,17
Contemporary uses of aloe vera gel, inner leaf juice, and decolorized leaf
juice include treatment of abrasions, burns, inflammation, insect bites,
psoriasis, skin irritations and fungal infections, UV-radiation damage; as an
emollient; as a common cosmetic ingredient, and as a wound-healing agent.3,5,6,14,17 The
use of the inner and decolorized whole leaf juices as commercial ingredients is
relatively new.
Internally, aloe vera leaf juices have been
used for diabetes, coughs and sore throat, kidney pains, digestive problems,
stomach ulcers, and jaundice. The yellow latex of the leaves is also used as a
laxative.3,5,17 Aloe
vera inner leaf is used as a general tonic for the circulatory, digestive, genitourinary,
and female reproductive systems, and in the treatment of fever, constipation,
obesity, conjunctivitis, joint inflammation, jaundice and hepatitis, menstrual dysregulation,
and tumors.6
1.9 Nomenclature considerations: The earliest confusion about the naming
of the aloe plant is described in the Old Testament. The name “tree aloe” refers
to a plant with an aromatic resin belonging to a different species in a
different family, Aquilaria agallocha (Thymelaeceae),
and the name “lign aloe” refers to A.
malaccensis.6,9 ‘Aloes’
in the New Testament (John 19: 39), however, refers to a material derived from
a true species of Aloe, Aloe perryi Baker (syn. Aloe succotrina Weston).9 Indeed, a number of aloe species were
used interchangeably in Europe to make purgative preparations.3,5,6,14,17 In the past 100 years, many aloe species were clumped
generically with the name “aloe” and considered synonyms. Socotrine aloe
(Socotra), Curaçao aloe, bitter aloe, and Cape aloe were interchangeable
vernacular names given to various species of Aloe including A. perryi,
A. vera, A. ferox and hybrids of A.
ferox, with A. africana and A. spicata considered synonyms in the
past.4
The United States Pharmacopeia (USP)
official Aloe monograph for over-the-counter stimulant laxative drugs still
includes several aloe species (A. vera, A. ferox, or hybrids of A. ferox
with A. africana
and A. spicata)
in its description,16 as do other pharmacopeias in Europe and
other parts of the world.5,17 In the American health food and cosmetic markets A. vera is the predominant species used.
The term “aloe vera” in this bulletin will be used generically in reference to the
Aloe vera species. The nomenclature
of ingredients used in labels of aloe products have lacked uniformity and
precision. The IASC suggests all aloe vera products must include the
Standardized Common Name “aloe vera” and specify the plant part/type of
ingredient (i.e., “leaf” if the leaf is used in its entirety or “inner leaf”).
2 Market
2.1
Importance in the trade:
In 2003, IASC estimated that raw material sales of aloe vera leaf and
leaf-derived ingredients were between $70-90 million globally with 35% growth
expected over the next five years. At that time, the United States was by far
the largest single seller of aloe vera as an ingredient with 60-65% of total
sales, with Latin America constituting another 20-25%, and Asia and the Pacific
Rim (Australia, China and India) together making up 10% of the market. Trade in
finished products containing aloe ingredients, was estimated to be over $35
billion globally in 2003.18 The importance of aloe vera as a source
for ingredients in the food, cosmetic, dietary supplement, and personal care
industries was emphasized by the market research company IMARC which reported
that the global market value for aloe vera ‘gel’ was US $507 million in 2017.19
2.2
Supply sources: Aloe vera
is extensively cultivated in many parts of the world, but Thailand, Mexico, and
the United States continue to be the largest producers of aloe vera ingredients.
According to two reports, Thailand is the biggest producer of aloe vera gel,
accounting for around one-third of the total global production. More recently,
China has emerged as an important supplier for aloe vera. Other leading
producers in the North, Central, and South American region include Mexico,
Dominican Republic, the United States, and Costa Rica.20 African countries with the largest aloe
vera production include Nigeria and Kenya.21
2.3
Market dynamics: A recent
report from the IMARC Group, a market research company, indicated that the
global aloe vera ‘gel’ market was worth US $465 million in 2016, growing at a
Compound Annual Growth Rate (CAGR) of around 11% during 2009-2016.20 The market seems to have been growing
steadily over the last decade, driven by varied and increasing usage of aloe vera
leaf juices in food, health care, and cosmetic industries with the healthcare
and personal care sectors being the two biggest drivers of aloe vera juice
ingredient consumption.20,22,23 (J. Wilson [IASC] email, June 28, 2017)
According
to Future Market Insights (FMI), a provider of syndicated marketing research
reports, the global aloe vera ingredient market is segmented, based on product
type into various forms: aloe vera leaf juice, inner leaf juice, and others. In
2015, the aloe vera leaf juices segment dominated the market in terms of value
and volume, and it is expected to remain dominant over the forecast period (up
to 2026). Meanwhile, the aloe vera (whole) leaf juice segment is expected to
expand at the highest CAGR in terms of value during the forecast period.21
3 Adulteration
3.1 Known adulterants: Materials used to adulterate aloe vera inner
leaf juice and juice powder include undeclared amounts of other aloe species
and juice made from whole aloe vera leaf. Substitution of dried powdered aloe
leaf juices with undeclared maltodextrin or sucrose has also been reported.6,24-27 (R. Gallego [Aloecorp] email to S. Gafner, April 2, 2019) The
AOAC Standard Method Performance Requirements (SMPR)® document for identification
of Aloe vera in dietary supplements and
dietary ingredients requires analysis for presence of undeclared carrageenan, gum
arabic (Acacia senegal and other Acacia spp., Fabaceae), and locust bean gum
(Ceratonia siliqua, Fabaceae) in
addition to maltodextrin. Despite their listing in the SMPR, the use of thickeners
like carrageenan, gum arabic, or locust bean gum as aloe vera adulterants has limited
evidence in the literature.28
According to IASC labeling guidelines, products
labeled “aloe vera inner leaf juice” should consist solely of the liquid from
the inner leaf from which the aloe exudate (latex) has been removed. Further,
IASC proposes that the concentration of aloins A and B (the primary aloe vera
anthrones) in aloe leaf dry juice be reduced to less than 10 ppm (parts per
million).2 Isocitrate (isocitric acid), which is
more abundant in the aloe rind than the inner leaf, was established by IASC as
a negative marker for the inner leaf. IASC also states that aloe vera leaf
juice products that contain more than 5% dry weight of isocitric acid should be
labeled as “aloe vera leaf juice,” not “aloe vera inner leaf juice”.1,6 While IASC has proposed definitions and
guidance for how aloe vera leaf-derived products should be described and
labeled, not all products claim compliance with IASC. IASC also is not a
regulatory body and so compliance with IASC guidelines is voluntary.
A number of other Aloe species are traded commercially and
are sometimes not accurately declared as to proper species. Aloe species traded
include A. ferox, A. arborescens, and A.
perryi according to the American Herbal Pharmacopoeia (AHP) monograph on
aloe.6 The American
Herbal Products Association’s Herbs of Commerce, 2nd edition,7 provides clear differentiation of
common names used for these species and include cape aloe (A. ferox), Aloe littoralis
(A. littoralis), Perry’s aloe (A. perryi), Aloe spicata (A. spicata),
and aloe vera (A. vera) as the aloes
in trade.
3.2
Additional IASC quality parameters: Low
quality aloe vera leaf and inner leaf juice ingredients may be due to
decomposition or dilution with water. IASC has established specific standards
of product strength. The minimum requirement for an aloe vera juice is 1% total
aloe solids in aloe vera leaf juice and 0.5% total aloe solids for inner leaf
juice ingredients.6,29 The soluble solids value is an
important quality indicator, because low values for solids suggest adulteration
by dilution with water.24 In addition, bulk aloe vera ingredients
need to contain a minimum of 5% acemannan calculated by dry weight.27
The
presence of acetic acid is indicative of the degradation of acetylated
polysaccharides. Lactic acid levels of more than 10% are indicators of
bacterial activity, likely due to contamination with Lactobacillus species. The presence of succinic and fumaric acids
indicates enzymatic degradation of the polysaccharides.27
3.3 Sources of information
supporting confirmation of adulteration: In the 1990s, spray-dried aloe vera juice with maltodextrin
was sold as 100% aloe vera juice, constituting a fraudulent misrepresentation.
This fraud was possible because many members of the industry promoted an
analytical method for aloe quality termed the Methanol Precipitable Solids (MPS)
test despite all scientific evidence that the test is not useful.24 (See section 3.7)
In the
early 1990’s IASC started channeling efforts to protect both the industry and
the consumer with the focus on the development of an aloe standard produced by
the Aloe Research Foundation (ARF), an industry-sponsored organization with the
goal to further research on aloe vera’s biological activities. Analysis of commercial
aloe vera ingredients was compared to the aloe vera ARF standard using a
chromatographic procedure developed by Pelley et al. in 1993.30 The first analysis indicated that the
quality of commercial aloe vera ingredients was variable and not always
accurately represented on the label or the certificate of analysis. Although no
details of the number of samples tested and degree of adulteration were
provided, the conclusion was that many commercial aloe ingredients in the
marketplace were adulterated with undeclared maltodextrin.24,30,31
In 1998,
18 commercially available aloe vera samples in the US marketplace were analyzed
at the University of Mississippi, School of Pharmacy, using size exclusion
chromatography. Half of the samples contained no or only trace amounts of the
main polysaccharide component in aloe vera.32
The same
year, Kim et al, analyzed 21 commercial aloe vera ingredients in Korea, also confirming
adulteration with undisclosed maltodextrin in over 30% of the samples.25
An investigative
report, published in 2003 by Nutraceuticals
World, concluded that adulteration was a serious problem in the aloe vera
business, detailing how adulteration of aloe vera ingredients occurs and the economic
incentive for such adulteration.18
In
Europe, aloe vera samples, obtained from pharmacies and other commercial venues,
were analyzed by the German Federal State of Baden-Württemberg’s food control
office.33 Their report confirmed that 17 out of
24 high-priced aloe vera products contained no significant amount of aloe vera ingredients
and were adulterated with large amounts of undisclosed sorbic and benzoic acids
while being marketed as “aloe juices and gels” dietary supplements.
An
analysis of 3 commercial aloe vera leaf solid raw materials and 12 commercial
aloe vera products, with a newly developed spectrophotometric method to assess
polysaccharide content, showed that 6 out of 12 commercial aloe vera products
contained less than 20% (range 0.58-18.83%) of the active original aloe vera polysaccharide
found in fresh whole aloe vera leaf.28
In
another study conducted in Switzerland, nine aloe vera ingredient samples of leading
international suppliers were examined by nuclear magnetic resonance (NMR) and
compared with fresh aloe vera leaf gel. Only three samples were found to have
acceptable levels of acemannan, the main aloe vera leaf polysaccharide.34
In another
NMR study, the authors commented on the large percentage of aloe vera products
adulterated with maltodextrin and suggested that NMR should be the method of
choice to assess quality control (QC) of the samples.35
The International
Agency for Research on Cancer (IARC) aloe vera monograph and the AHP Aloe vera leaf, Aloe vera leaf juice, Aloe
vera inner leaf juice standards of identity, analysis, and QC monograph describe
the use of maltodextrin in the manufacturing process and state that it is added
to artificially enhance polysaccharide content. They also state that this has historically
been one of the most common adulterants in aloe vera inner leaf juice products.6,36
In an article
published by Nutraingredients-USA on Npve,ber 12, 2012, and updated on September
26, 2016, Roy Upton (AHP) indicated in reference to aloe vera products in the
marketplace that: “results that come back from analytical labs show that a
number of ‘aloe’ products on the market contain little (in some case, none) of
the actual plant.”22
A Bloomberg News report of November 22,
2016 mentioned four samples of store-brand aloe gel purchased at national
retailers showed no indication of the presence of aloe vera compounds in
various lab tests. All products listed aloe barbadensis leaf juice — another
name for aloe vera — as either the No. 1 or No. 2 ingredient (on the label) after
water.37 Aloe vera’s three inner leaf chemical
markers — acemannan, malic acid, and glucose — were absent in the tests of three
products based on NMR tests conducted by an anonymous lab hired by Bloomberg News. The three samples analyzed
contained maltodextrin. The fourth aloe gel contained malic acid, but not acemannan
and glucose.37
After
this report, several law firms filed lawsuits against four retailers after
separate testing failed to find aloe vera chemical marker compounds in the
companies’ private-label products. The plaintiffs are seeking class-action
status and (asking for) restitution for all the customers who they say were
misled.37,38 One of the cases was dismissed at least
in part based on the argument that acemannan levels can decrease depending on
the storage conditions, which may not be under full control by the companies
selling the aloe vera products.39
Alkemist
Labs, a third-party contract analytical laboratory, shared a summary of their thin-layer
chromatography (TLC) reports of 2015-2017, indicating they have “failed”
samples because they contained a high content of maltodextrin. Sidney Sudberg,
president and CSO of Alkemist Labs, said “Most of the time, we do not get any
indication of whether the manufacturers use maltodextrin as an undeclared excipient,
so we may be failing samples when the maltodextrin appears to exceed the aloe (content),
chromatographically speaking.” (S. Sudberg [Alkemist Labs] email, June 29, 2017)
IASC
tests every aloe vera ingredient sold by an IASC member to ensure it has a minimum
of 5% acemannan content by dry weight, as well as the presence of markers
glucose and malic acid. A spokesperson states that IASC has not seen an adulteration
issue recently, but the problem seems to be frequent on products from companies
that are not IASC certified. (J. Wilson [IASC] email, June 28, 2017).
IASC
Executive Director Jane Wilson added: “I am not aware of any
recent reporting of adulteration with other aloe species. The responsible
industry continues to be concerned with suppliers marketing aloe raw materials
containing undeclared maltodextrin, as well as the use of poor quality aloe and
"fairy-dusting" in aloe finished products. IASC conducts its
certification program, and we have not had any products fail due to a
documented case of adulteration, but of course this may not be representative
of the market as a whole. Obviously companies who may want to cheat are not the
ones that subject themselves to outside scrutiny.” (J. Wilson [IASC] email, April 23, 2019)
3.4
Accidental or intentional adulteration: Both types (or means) of adulteration, accidental and
intentional, are known to occur in the marketplace. The use of undeclared maltodextrin
and preservatives is clearly intentional. Intentional adulteration is also easily
carried out through the addition of excess water to juices or powders. The
reasons for economically motivated adulteration are clearly stated in the
German report from 2003: “High quality Aloe
vera gel, containing 0.5-1.3% solid material, currently sells for $1.25 – $1.95
per kg (wholesale price) as non-concentrated pure juice. Whole leaf extract
(0.95-2.0% solid matter) is available for $2.00 – $4.00 per kg. Usually, 10x to
40x concentrated gel is supplied. Powder (200x concentrate) sells for $225 – $305
per kg for IASC-certified material. However, aloe vera juice powder can be
purchased for as little as $60, but it is likely to contain up to 60%
maltodextrin, which is acceptable as long as it is appropriately labeled.”18 High quality 1x (single strength - neither
diluted nor concentrated) aloe vera juice sold for approximately $1.45 – $2.00
per kg in 2018. Based on an informal investigation by this author, the spray-dried
powders coming from inner aloe juice are running from $235 per kg for small
amounts to about $140 for over 500 kg orders. Costs of (whole) aloe vera leaf juice
ingredients fluctuate greatly. Spray-dried aloe vera leaf juices range from $90
– $160 and unconcentrated decolorized aloe leaf juice can be priced as low as
$18.
3.5 Frequency of occurrence:
Several investigations
from 1998 to 2016 in different countries suggest that adulteration of aloe vera
inner leaf juice is very frequent.25,28,32,33 The quality of the products varied, with some studies
reporting that up to 50% of the commercial products tested are adulterated.32 However, recent results from testing
361 powdered aloe vera leaf juice products by high-performance liquid
chromatography (HPTLC) at Alkemist Labs, found that only 11 products (3%) were
clearly adulterated with maltodextrin, meaning that they consisted solely of
maltodextrin, or maltodextrin was present in amounts that made an accurate
identity determination impossible. (S. Sudberg [Alkemist labs] email, June 29,
2017 and January 7, 2019)
3.6 Possible safety/therapeutic
issues: Although anthrones
from aloe vera latex found in the rind of the aloe vera leaf or other aloe
species have a history of use for medicinal purposes, mainly as a laxative,
their presence at relatively high concentrations in aloe vera food and
supplement products may be responsible for some reported adverse effects.36,40,41 The main adverse effect is diarrhea with consequent loss
of fluid and electrolytes, but impacts on microbiota and mucosa architecture due
to the cytotoxicity, mutagenicity, and carcinogenicity of anthrones after
prolonged exposure have been observed in in
vitro and animal studies.40 The European Food Safety Authority
(EFSA) published a safety assessment of hydroxyanthracene derivatives,
including anthrones from aloe vera, used in food supplements in 2018, and based
on limited data collected and reviewed, EFSA Food Additives and Nutrition Sources
Panel concluded no safe intake levels can be established.42 While insufficient data are available to
assess the carcinogenicity of non-decolorized aloe vera leaf juice in humans,
IARC has classified non-decolorized aloe vera whole leaf extract as a possible
human carcinogen.36
In the United
States, aloe vera in food and supplement products is either derived from inner
leaf or decolorized leaf preparations in which anthrones are largely removed. It
is crucial to monitor the content of these compounds in aloe vera leaf juice ingredients.40,43 The IASC standard suggests a maximum allowable aloin
content in aloe vera-derived material for oral consumption of less than 10 ppm;
for non-medical use, the recommended limit is 50 ppm or lower.2,29
No
safety issues are known from adulteration of aloe vera with maltodextrin,
glucose, sucrose, glycerin, and/or malic acid or after decomposition of aloe
vera ingredients producing acetic, succinic, and/or lactic acids. However, some
of the purported benefits of aloe vera may be diminished by excessive dilution
of aloe vera polysaccharides with water, or the replacement of aloe vera
polysaccharides with maltodextrin.
3.7 Analytical methods to
detect adulteration: Several Aloe species
including A. ferox, A. arborescens, and A. perryi are traded commercially and sometimes they are marketed
as A. vera. The various species of
aloe that appear in trade are readily differentiated by the morphology of the
leaf and the color, size and location, of the “teeth,” and can be authenticated
macroscopically.6 In addition, the presence
of maltodextrin is readily detected by microscopic means. In cases where macro-
or microanatomical features are lacking, chemical and genetic testing methods
may be used to authenticate ingredients derived from aloe vera leaf (see
below).
Ionic
strength
A quick test to assess the
adulteration of an aloe vera juice ingredient is to measure its ionic strength
(conductivity). There is a direct correlation of the sum of the sodium,
potassium, calcium, and magnesium cations per mg/L and the ingredient’s
conductivity. Maltodextrin has a much lower conductivity than spray-dried aloe
vera powders.24 Therefore, conductivity measurements provide
a low-cost and rapid substitute for the analysis of the individual ions, e.g.,
by atomic absorption spectroscopy or inductively coupled plasma-mass
spectrometry (ICP-MS).24,30
Colorimetric assays
A colorimetric
assay can be used as an initial screening tool for identifying potentially
adulterated aloe vera juice ingredients with maltodextrin. This is a method commonly
known as starch detection method using an iodine/potassium iodide reagent. Depending
on the amount of maltodextrin present, the solution will turn medium to dark brown
or purple to black.6 Another quick quantitative colorimetric
assay was developed for the determination of acemannan in aloe vera ingredients
and products based on the formation between β-glucans and the azo dye Congo red.
The reaction between the dye and aloe acemannan leads to a substantially more
intense color reaction than with adulterating materials such as maltodextrin,
locust gum, or gum arabic.28 However, the method may be
fooled by addition of undeclared β-glucans from other sources.
A different
colorimetric approach takes advantage of the formation of a
ferric-acetohydroxamic complex after reaction of the aloe acemannan with
hydroxylamine and subsequent complex formation with ferric chloride. The submission of a validation
report enabled it to achieve AOAC Official Method First Action status with the
proviso that its use is limited to the analysis of processed raw materials and
not finished products.44 As with other colorimetric
methods, the hydroxylamine/ferric chloride method lacks specificity. The color
reaction is not only obtained with aloe acemannan, but also with other
acetylated substances, which could be used to manipulate the results.
Chromatographic
assays
The AHP and the HPTLC
Association provide details of an HPTLC method to distinguish A. vera leaf from leaves of A. ferox and A. arborescens.6,45 In addition, the AHP monograph includes
fingerprints for aloe vera leaf, outer leaf, inner leaf, and various
IASC-certified commercial aloe vera ingredients.6 TLC methods to authenticate aloe vera
leaf juice and ‘gel,’ and to detect adulteration in commercial products have
also been published by Kim et al. and Lachmeier et al.25,33
High-performance
liquid chromatography (HPLC) is most often used to quantify aloins A and B in
aloe vera leaf juice products. Two HPLC methods were subjected to a
single-laboratory validation according to guidelines of AOAC International, one
of which was approved as an AOAC Official Method First Action status.6,46,47 These methods allow to
evaluate compliance of aloe vera products with the IASC for anthrone content. Kim
et al. published an HPLC-refractive index (RI) method to determine maltodextrin
in 21 aloe leaf ‘gel’ products, and found undeclared maltodextrin (45.0-94.6%)
in eight samples.25 However, since the
maltodextrin peaks elute over a time span of about 16 minutes, the accurate
quantification of maltodextrin in aloe vera leaf samples using this method by
HPLC remains challenging. The determination of the isocitric acid contents can
be used to distinguish products made with aloe rind or whole leaf from those
made solely from the inner leaf.48
Another approach
to determine the presence of maltodextrin in aloe vera leaf ingredient samples
is the quantification of glucose, galactose, and mannose by gas chromatography
(GC) after hydrolysis of larger polysaccharides (separated using a molecular
weight filter of 5000 Da) and subsequent silylation.25 Large amounts of glucose
(relative to mannose) and absence of galactose are indications of materials
that contain large amounts of maltodextrin. A headspace-SPME-GC/MS method developed
by researchers in Germany has been used to evaluate 24 aloe vera beverages. The
report explains how to determine authenticity (identity, adulteration,
excessive dilution with water) undeclared preservatives, and quantify aloin in
aloe vera beverages.33
Two publications have
detailed methods to measure aloe vera polysaccharides in commercial
preparations using size exclusion chromatography (SEC) with refractive index
detection or multi-angle laser light scattering detection (MALLS).32,49 The peak distribution from the analysis of commercial aloe
vera liquids and powders provided highly variable results.49,50 Therefore, it is unclear if the published methods are
useful for the distinction among Aloe
spp., or for the detection of undeclared maltodextrin.
Methanol precipitable
solids
The MPS
test measures polysaccharides plus a complex of alcohol insoluble salts and
organic acids in aloe vera leaf juices gravimetrically after precipitation and
subsequent evaporation of the solvent. The values for
"polysaccharide" generated by this test are substantially higher than
the actual levels measured by other tests. Since the assay measures every
molecule that is precipitated with methanol, it is easily fooled by the
addition of extraneous materials, in particular other polysaccharides such as maltodextrin.24 Despite these limitations, many
companies may still rely on MPS values for quality control and even suggest their
products are better than others when their MPS value is higher.
Spectroscopic assays
Diehl and Teichmüller were
the first to suggest 1H NMR as a tool to assess identity and quality of aloe vera leaf preparations.31 A
single-laboratory validation of an NMR method for the determination of aloe
vera polysaccharides was published in 2009.35 In 2010, an 1H
NMR method for quality control of aloe vera products was developed and
validated by research groups from industry and academia.51 The procedure allows quantifying
acetylated polysaccharides, glucose, malic acid, lactic acid, and acetic acid
in aloe vera products to meet quality control specifications per IASC
requirements. The presence of degradation products (e.g., lactic acid, succinic
acid, fumaric acid, acetic acid, formic acid, and ethanol), preservatives
(potassium sorbate, sodium benzoate, and citric acid/citrate), and other
atypical impurities, additives, or adulterants (e.g., methanol, glycine,
glycerol, sucrose, maltodextrin, propylene glycol, ethanol) can also be
evaluated.
The method
published by Jiao et al.51 was expanded by adding
cesium-EDTA, which allows the determination of magnesium, calcium, and fructose
in addition to the compounds mentioned above.52 Most recently, the AOAC
SMPRs for identification of Aloe vera
in dietary supplements and dietary ingredients specifically listed four potential
aloe vera adulterants: maltodextrin, carrageenan, gum arabic, and locust gum.53 Using 1H NMR,
all four potential adulterants were detected at levels of 10% and above in
decolorized aloe vera leaf extract.54
NMR provides
advantages over separation-based test methods in that it is rapid, allows for
specific recognition of molecules, and requires minimal sample preparation.51 The disadvantage is that it
is not a testing platform that is integrated into most commercial laboratories.
An authoritative
reference for authentication and detection of adulterants of aloe vera leaf
derived ingredients, with a specific emphasis on aloe vera leaf juice products
that are compliant with IASC standards was produced by AHP in 2012. The AHP
Aloe monograph details a variety of analytical methods and standards to
authenticate ingredients made from aloe vera leaf, and to detect the most
common adulterants.6
Genetic Methods
Some
preliminary attempts are being made to develop DNA methodologies to detect aloe
vera adulteration. A test for identification of eight Aloe species, including A.
vera, A. arborescens, and A ferox, was developed using the Random
Amplified Polymorphic DNA (RAPD) technique.55 Using this technique may be useful in
combination with other analytical methods to help identify aloe samples
containing DNA, but may not be a solution for the evaluation of processed aloe vera
leaf ingredients if there is no DNA of sufficient quality to allow unambiguous
authentication.55
4 Conclusions
Aloe
vera leaf and inner leaf juice ingredient products are widely used for their
healing properties, both for internal use and in a wide array of topical products.
There is significant nomenclatural confusion among different aloe vera derived
materials. The IASC has attempted to establish a clear distinction between
unfiltered anthrone-rich aloe vera leaf products and those that are decolorized
to contain less than 10 ppm of aloins.21,22 The marketplace importance of aloe vera
products rich in aloins is low in the United States and internationally.
The
main motivation for aloe vera adulteration is economic, i.e., the dilution of leaf
and inner leaf powder with undeclared maltodextrin or sucrose, or of liquids with
excessive amounts of water. Also observed is the substitution/admixture of aloe
vera inner leaf with aloe vera (whole) leaf. Companies and individuals involved
in the purchase, trade, or quality control of aloe vera leaf ingredients should
be aware of the quality requirements and of existing adulteration issues, and take
the necessary precautionary measures to avoid purchasing, selling, or
manufacturing products made with adulterated aloe vera leaf materials.
5 References
- IASC
Labeling Guidance. The International Aloe Science Council (IASC); 2009. http://www.iasc.org/Portals/19/Documents/Members/10_0405_IASC_Labeling_Guidance_Definitions.pdf.
Accessed May 4, 2018.
- The
International Aloe Science Council presents: An aloe scientific primer. The
International Aloe Science Council (IASC); 2009. http://www.iasc.org/Portals/19/Documents/Scientific/IASC_Aloe_vera_A_Scientific_Primer.pdf.
Accessed February 13, 2019.
- Aloe
vera and aloe gel. WHO Monographs on Selected
Medicinal Plants. Vol 1. Geneva, Switzerland: World Health Organization;
1999.
- Youngken
HW. Textbook of Pharmacognosy, 6th ed. Philadelphia, PA: The Blakiston
Company; 1948.
- Blumenthal M, Busse WR, Goldberg A, Gruenwald J,
Hall T, Riggins CW, Rister RS, eds. Klein S, Rister RS, trans. The Complete German Commission E. Monographs—Therapeutic
Guide to Herbal Medicines. Austin, TX: American Botanical Council; Boston: Integrative
Medicine Communication; 1998.
- Upton
R, Axentiev P, Swisher D. American Herbal
Pharmacopoeia and Therapeutic Compendium: Aloe Vera Leaf, Aloe Vera Leaf Juice,
Aloe Vera Inner Leaf Juice, Aloe vera
(L.) Burm. f. Standards of Identity, Analysis, and Quality Control. Scotts
Valley, CA: American Herbal Pharmacopoeia; 2012.
- McGuffin
M, Kartesz JT, Leung AY, Tucker AO. Herbs
of Commerce. 2nd ed. Silver Spring, MD: American Herbal Products
Association; 2000.
- Tropicos.org.
Missouri Botanical Garden. https://www.tropicos.org/Name/34000217. Accessed
January 17, 2019.
- Olwen
MG, Ronell RR, Figueiredo E, Smith GF. The
Aloe Names Book. Pretoria, South Africa: National Biodiversity Institute, S
A N B I; 2011.
- Melzig
MF, Hiller K, Loew D. Aloe barbadensis.
In: Blaschek W, ed. Wichtl — Teedrogen
und Phytopharmaka. Stuttgart, Germany: Wissenschaftliche
Verlagsgesellschaft mbH; 2016:63-66.
- Mills
S, Bone K. Turmeric. Principles and
Practice of Phytotherapy: Modern Herbal Medicine. Edinburgh, Scotland:
Churchill Livingstone Elsevier; 2013:900-922.
- Aguilar
A, Camacho JR, Chino S, Jácquez P, López ME. Herbario medicinal del Instituto Mexicano del Seguro Social. Mexico
City, Mexico: Instituto Mexicano del Seguro Social; 1994.
- Aloe vera (L.) Burm.f. The Plant List.
Version 1.1. http://www.theplantlist.org/tpl1.1/record/kew-298116. Accessed
June 12, 2017.
- Engels
G. Aloe. HerbalGram. 2010;87:1-5.
- Medel
Zavala AE, Ortiz-Velazquez JR. Estudio de
factibilidad para el cultivo de sabila (Aloe vera) en San Luis Potosí. San Luis Potosí, Mexico: Facultad de
Economía, Universidad Autonoma de San Luis Potosí; 2006.
- Aloe.
USP 42-NF 37. Rockville, MD: United
States Pharmacopeial Convention; 2019:140-141.
- European
Medicines Agency. Community herbal monograph on Aloe barbadensis Miller and on Aloe
(various species, mainly Aloe ferox
Miller and its hybrids) London: European Medicines Agency Committee on Herbal
Medicinal Products (HMPC); 2006:1-9.
- Herzberg
F, Gruenwald J. Aloe vera: An
international success story. A glimpse of the international aloe market. Nutraceuticals World [online]: Rodman
Media; 2003.
- Aloe
vera gel market: Global industry trends, share, size, growth, opportunity and
forecast 2018-2022 [press release]. Arlington, VA: IMARC Group2018.
- IMARC,
2017 Aloe vera gel market: Global industry trends, share, size, growth,
opportunity and forecast 2017-2022. International Market Analysis Research and
Consulting Group; 2017:1-48.
- Global
demand for Aloe vera extracts to
reach 60,720 tonnes in 2016; Emergence of innovative, high-quality and
cost-effective products ramping up adoption. 2016; http://www.futuremarketinsights.com/press-release/aloe-vera-extracts-market.
Accessed January 10, 2018.
- Schultz
H. Global aloe market estimated at 13 billion. Nutraingredients USA [online]: William Reed Business Media, Inc.;
2012.
- Watson
E. Improve USA: Aloe is already the biggest botanical on the planet but it's
about to get even bigger. Nutraingredients
[online]: William Reed Business Media, Inc.; 2012.
- Waller
TA, Pelley RP, Strickland FM. Industrial processing and quality control of Aloe barbadensis In: Reynolds T, ed. Aloes, The Genus Aloe. Boca Raton, FL:
CRC Press LLC; 2004:139-205.
- Kim
KH, Lee JG, Kim DG, et al. The development of a new method to detect the
adulteration of commercial aloe gel powders Arch
Pharm Res. 1998;21(5):514-520.
- Yaron
A. Characterization of Aloe vera gel
before and after autodegradation, and stabilization of the natural fresh gel. Phytother Res. 1993;7(7):S11-S13.
- Certification
Program Policies & Operational Procedures. The International Aloe Science
Council (IASC); 2012. http://www.iasc.org/Portals/19/Documents/Certification/12_0312_IASC%20Certification%20Program_SOP_EDIT.pdf?ver=2016-06-30-215036-090.
Accessed May 8, 2018.
- Eberendu
AR, Luta G, Edwards JA, et al. Quantitative colorimetric analysis of aloe
polysaccharides as a measure of Aloe vera
quality in commercial products. J
AOAC Int. 2005;88(3):684-691.
- Aloe vera Quality Standard The
International Aloe Science Council (IASC); 2015. http://www.iasc.org/Portals/19/Documents/Certification/AloeVeraQualityStandard.pdf?ver=2015-09-01-113340-987.
Accessed May 8, 2018.
- Pelley
RP, Wang Y-T, Waller TA. Current status of the quality control of Aloe barbadensis extracts. SÖFW Journal 1993;119(5):255-268.
- Diehl
B, Teichmüller EE. Aloe vera, quality inspection and identification. Agro Food Ind Hi-Tech. 1998;9(1):14-16.
- Ross
SA, ElSohly MA, Wilkins SP. Quantitative analysis of Aloe vera mucilaginous polysaccharide in commercial Aloe vera products. J AOAC Int. 1997;80(2):455-457.
- Lachenmeier
K, Kuepper U, Musshoff F, Madea B, Reusch H, Lachenmeier DW. Quality control of
Aloe vera beverages. Electron J Environ Agric Food Chem. 2005;4(4):1033-1042.
- Bozzi
A, Perrin C, Austin S, Arce Vera F. Quality and authenticity of commercial aloe
vera gel powders. Food Chem. 2007;103(1):22-30.
- Davis
B, Goux WJ. Single-laboratory validation of an NMR method for the determination
of Aloe vera polysaccharide in
pharmaceutical formulations. J AOAC Int. 2009;92(6):1607-1616.
- Aloe Vera. Some drugs and herbal products: IARC monographs on the evaluation of
carcinogenic risks to humans. Vol 108. Lyon, France: International Agency
for Research on Cancer (IARC); 2016:37-71.
- Mulvany
L, Faux Z. No evidence of Aloe vera found
in the Aloe vera at Wal-Mart, CVS.
Wal-Mart, Target, CVS sell aloe without appearance of plant. Bloomberg News [online]. New York, NY:
Bloomberg L.P.; 2016.
- Patricia Bordenet vs CVS Health Corporation.
Case: 1:16-cv-06103, June 10, 2016 (Illinois Northern District Court).
- Family
Dollar aloe vera false advertising class action tossed, for now. Top Class
Actions, LLC; 2018. https://topclassactions.com/lawsuit-settlements/lawsuit-news/845951-family-dollar-aloe-vera-false-advertising-class-action-tossed-now/.
Accessed February 20, 2019.
- Boudreau
MD, Olson GR, Tryndyak VP, Bryant MS, Felton RP, Beland FA. From the cover:
Aloin, a component of the Aloe vera
plant leaf, induces pathological changes and modulates the composition of
microbiota in the large intestines of F344/N male rats. Toxicol Sci. 2017;158(2):302-318.
- Gardner
Z, McGuffin M. American Herbal Products
Association’s Botanical Safety Handbook. 2nd ed. Boca Raton, FL: CRC Press;
2013.
- Younes
M, Aggett P, Aguilar F, et al. Scientific opinion on the safety of
hydroxyanthracene derivatives for use in food. EFSA Journal. 2018;16(1):5090-5187.
- Shao
A, Broadmeadow A, Goddard G, Bejar E, Frankos V. Safety of purified decolorized
(low anthraquinone) whole leaf Aloe vera
(L) Burm. f. juice in a 3-month drinking water toxicity study in F344 rats. Food Chem Toxicol. 2013;57:21-31.
- Metcalfe
C. Quantitation of Aloe vera polysaccharides
by O-acetyl and UV-Vis spectrophotometry: First action 2018.14. J AOAC Int. 2019.
- Barbados
aloes (Aloe barbadensis). HPTLC
Association. Aloe_barbadensis_Barbados_Aloes_HPTLC_Association_31_Aug_17.pdf.
Accessed January 8, 2019.
- Brown
PN, Yu R, Kuan CH, Finley J, Mudge EM, Dentali S. Determination of aloin A and
aloin B in Aloe vera raw materials
and finished products by high-performance liquid chromatography:
Single-laboratory validation. J AOAC Int.
2014;97(5):1323-1328.
- Kline
D, Ritruthai V, Babajanian S, et al. Quantitative analysis of aloins and
aloin-emodin in Aloe vera raw
materials and finished products using high-performance liquid chromatography:
single-laboratory validation, first action 2016.09. J AOAC Int. 2017;100(3):661-670.
- Zhang
Y, Bao Z, Ye X, et al. Chemical investigation of major constituents in Aloe vera leaves and several commercial
aloe juice powders. J AOAC Int. 2018;101(6):1741-1751.
- Turner
CE, Williamson DA, Stroud PA, Talley DJ. Evaluation and comparison of
commercially available Aloe vera L.
products using size exclusion chromatography with refractive index and
multi-angle laser light scattering detection. Int Immunopharmacol. 2004;4(14):1727-1737.
- He
K, Mergens B, Yatcilla M, et al. Molecular weight determination of aloe
polysaccharides using size exclusion chromatography coupled with multi-angle
laser light scattering and refractive index detectors. J AOAC Int. 2018;101(6):1729-1740.
- Jiao
P, Jia Q, Randel G, Diehl B, Weaver S, Milligan G. Quantitative 1H-NMR
spectrometry method for quality control of Aloe
vera products. J AOAC Int. 2010;93(3):842-848.
- Monakhova
YB, Randel G, Diehl BWK. Automated control of the organic and inorganic
composition of Aloe vera extracts
using 1H NMR spectroscopy. J AOAC Int. 2016;99(5):1213-1218.
- Ingle
P, Barrett B, Betz JM, et al. AOAC SMPR® 2017.010. J AOAC Int. 2017;100(4):1187-1188.
- Lee
I, Vo J, Ma H, et al. Detection and determination of adulterants in Aloe vera using NMR and FTIR techniques.
132nd AOAC International Annual Meeting & Exposition; 2018; Toronto, ON,
Canada.
- Ezzat
SM, El Sayed AM, Salama MM. Use of random amplified polymorphic DNA (RAPD)
technique to study the genetic diversity of eight Aloe species. Planta Med. 2016;82(15):1381-1386.
REVISION SUMMARY
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Ezra Bejar
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