jaoac1741.pdf

Zhang et al.: Journal of AOAC International Vol. 101, No. 6, 2018 1741
Background: There are a substantial number of
papers in the scientific literature reporting on the
chemical composition of the Aloe vera plant. None
of these investigations are truly comprehensive nor
address the differences in composition that occur
through processing variations in fresh leaves and
commercially available product forms. Objectives:
This work was to analytically examine a range of these
forms and compile the findings. Methods: Fresh
A. vera leaves and a number of commercial aloe juice
powders were investigated for their major chemical
constituents. Samples included fresh leaves from
China and Mexico, plus commercial powders from
different manufacturers made from different plant
parts and/or manufacturing processes. The test results
include moisture, ash, fiber, protein, lipids, minerals,
organic acids, free sugars, and polysaccharides. The
analytical methods employed comprise inductively
coupled plasma-optical emission spectroscopy
for minerals, high-performance anion-exchange
chromatography equipped with pulsed amperometric
detection for free sugars, HPLC for organic acids, and
size exclusion chromatography (SEC)–multi-angle
laser light scattering (MALS)–differential refractive
index (dRI) for polysaccharide analyses. The absolute
MW and MW distribution were determined using MALS
measurement. Results: The major constituents of
A. vera fresh leaf are fibers, proteins, organic acids,
minerals, monosaccharides, and polysaccharides,
which accounted for 85–95% of the total composition
determined. In the commercial powdered aloe juice
samples, four major components—organic acids,
minerals, monosaccharides, and polysaccharides—
accounted for 78–84% of the total composition.
Apart from the four major components, products
manufactured by ethanol precipitation contained
high amounts of fiber and protein, while the free
sugars were removed. In ethanol-precipitated
Special Guest Editor Section
Guest edited as a special report on “Aloe vera: Chemistry, Major
Chemical Components, Quantification, and Molecular Weight
Determination of Polysaccharides” by Kan He.
Color images are available online at http://aoac.publisher.
ingentaconnect.com/content/aoac/jaoac
1
Corresponding author’s e-mail: qunyiz@herbalife.com
Chemical Investigation of Major Constituents in Aloe vera
Leaves and Several Commercial Aloe Juice Powders
Yuehong Zhang, Zhichao Bao, Xiaoyan Ye, and Zhaoyang Xie
Herbalife NatSource (Hunan) Natural Products Co. Ltd, Research and Development, 1318 Kaiyuan East Rd,
Xingsha, Changsha City, Hunan Province, People’s Republic of China, 410100
Kan He, Bill Mergens, Wenjie Li, Mike Yatcilla, and Qunyi Zheng
1
Herbalife Nutrition, Worldwide Research Development and Scientific Affairs, 950 West 190th St,
Torrance, CA 90502
DOI: https://doi.org/10.5740/jaoacint.18-0122
products, the polysaccharide MW was less affected
by manufacturing conditions and the concentration
of aloe polysaccharides was higher than in products
made in the nonethanol manufacturing processes. The
overall chemical profiles were found to be consistent,
except for the MW and content of polysaccharides in
the commercial aloe samples analyzed, which were
largely dependent on the types of manufacturing
processes employed. Conclusions: This present study
provides a comprehensive investigation of the major
chemical composition of A. vera leaf and commercially
derived products. The use of the SEC combined with
MALS and differential RI detectors has proved to
be an improved tool for the accurate determination
of polysaccharide MW and contents of the various
commercially available A. vera products in this study.
A
loe vera (L.) Burm.f. (Aloe barbadensis Miller) belongs
to Asphodelaceae family (1) and contains over 500 Aloe
species, but A. barbadensis and A. arborescens are the
two most popular commercially grown species in the world and
are widely used for various medical, cosmetic, and nutraceutical
purposes (2). Aloe leaves have a life span of about 12 years and
take approximately 4 years to reach maturity before harvesting
to be processed for aloe product manufacturing (3). The leaf
consists mainly of an outer green rind (skin) and an inner pulp or
mucilaginous gel.There is a vascular bundle in the leaf lining at the
junction between rind and inner pulp (4). The aloe leaf is the sole
plant component that has been used, and there are three aloe juice
products made according to the parts of the leaf used: juice from
entire leaf, juice from inner leaf, and latex from vascular tissue.
Whole leaf juice is manufactured by grinding and squeezing the
entire leaf to obtain the juice. The obtained juice then undergoes
sterilization, filtration, decolorization (activated charcoal
absorption), sterilization, concentration, and dehydration. The
inner leaf juice is obtained in a similar way as the manufacturing
of whole leaf juice, except that the outer rind is removed first (5).
Over 200 chemical constituents from aloe leaves have been
reported, including polysaccharides (6), minerals, sugars, organic
acids,vitamins,lignins,lipids,saponins,phytosterols,protein,and
amino acids (7–9). Of the latex derived from the vascular bundle,
over 100 compounds have been identified, which are mainly
chromones, anthraquinones, anthrones, tetrahydroanthracenones,
and anthrone/tetrahydroanthracenone glycosides, etc. (10–12).
Besides the latex, these composition studies have focused
Downloaded
from
https://academic.oup.com/jaoac/article/101/6/1741/5654109
by
guest
on
18
June
2023

1742 Zhang et al.: Journal of AOAC International Vol. 101, No. 6, 2018
on the active constituents in A. vera plant, such as acetylated
polysaccharides (acemannan); characteristic compounds, such as
organic acids including malic, citric, isocitric, and lactic acids,
for characterization and quality control of aloe ingredients; and
anthraquinones, mainly aloins A and B, which are considered
contaminants and must be removed from nonlatex aloe products.
A number of methods for aloe polysaccharide compositional
analyses have been published, which include colorimetric/
spectrophotometric, NMR spectroscopic, and gel permeation
chromatographic (GPC) analysis. A quantitative colorimetric
method using Congo Red dye (sodium 4, 4′-diphenyl-2,
2′-diazo-bis-1-naphtlamino-4-sulfonate) specifically measures
the β-linked glucomannan of A. vera with no need for prior
separation or chemical degradation of the polysaccharides. The
method is based on the interaction of the glucomannan with
Congo Red to form a characteristic color that can be assayed at
540 nm wavelength. The formed dye–polysaccharide complex is
proportional to the amount of glucomannan in the test sample and
is reported not to be interfered with by the other ingredients in
aloe product, such as, glycerin, ethanol, glucose, sodium chloride,
etc., nor by possible adulterants like maltodextrin, dextrin, guar
gum, locust gums, pectin, gum Arabic, arabinogalactan, inulin,
psyllium, etc. (13).Asimilar colorimetric method uses alizarin red
(1, 2-dihydroxyanthraquinone) to react with aloe polysaccharides
through the electrostatic and hydrophobic interactions and
produces a complex with maximum absorbances at 325 and
516 nm wavelength. Common impurities, such as guar gum,
locust gum, starch, or maltodextrin, or small molecules like
sucrose and glucose in commercial aloe products do not interfere
with the determination of aloe polysaccharides (14, 15).
One of the characteristic features of aloe polysaccharides is
that the polymer chain contains acetate groups on the mannose
moieties, acemannan.These acetate groups can be measured using
acolorimetricassay,inwhichtheacetylgroupsonpolysaccharides
are quantitatively reacted with alkaline hydroxylamine. The
formed acetohydroxamic acid is further reacted with ferric
trichloride giving ferric-acetohydroxamic acid complex, which
can be measured at 540 nm wavelength to determine the content
of acetyl groups (16). The resulting content of the acetate obtained
from the above method, however, comprises all the acetate groups,
not necessarily only those from the acetylated polysaccharides.
More selective and accurate results can be obtained by proton-
NMR spectroscopic measurement (1
H-NMR). In the
1
H-NMR
spectrum, the different acetate groups present signals that can be
utilized as the fingerprint of the A. vera. The content of acetyl
polysaccharides is measured by the determination of the content of
the acetates. Besides the acetylated polysaccharides, other major
components, such as malic acid, citric acid, isocitric acid, isocitric
acid lactone, lactic acid, glucose, fructose, and some minerals,
can also be assayed by 1
H-NMR. A recent publication reported a
method of using 1
H-NMR to quantitate two minerals, Mg
2+
and
Ca2+
, after addition of a Cs-EDTA solution into the aloe sample
and measurement of the signals derived from the mineral–EDTA
complex (17). The method validation and applications using
1
H-NMR on commercial aloe products can be found in literature
(18–22). While these methods are focused on the quantitation of
aloe polysaccharides, for the polysaccharide MW information,
size exclusion chromatography (SEC; or GPC) coupled with
different detectors, e.g., refractive index (RI) or light scattering,
are frequently employed to acquire such information. Analysis of
polysaccharide MW on 32 various A. vera samples from different
manufacturers using GPC coupled with an RI and a multi-angle
laser light scattering (MALS) detector were reported. Results by
MALS detection showed the MWs were from as low as 10 kDa to
a high of 740 kDa in the 32 measured samples (23).
For chemical compositions of A. vera leaf, a few publications
can be found in literature. Major chemical constituents of
A. vera plant in fillets, rind, and gel extracted from the fillets
were investigated. The main type of polysaccharides was
determined to be acetylated polysaccharides present in the
fillet and gel fractions. The rind tissue cell wall had a different
type of polysaccharide that contained a high level of mannosyl
and xylosyl residues. In addition to polysaccharides, the
distribution of other components, including lipids, proteins,
soluble sugars, fibers, ash, and major minerals in fillet, gel, and
rind, were reported (24). Another work reported the isolation of
components of cell wall, degenerated cellular organelles, and
liquid gel from the mesophyll cells of A. vera inner leaf. The
carbohydrate compositions of these components demonstrated
that the liquid gel mainly contained mannan, the microparticles
contained galactose-rich polysaccharide(s), and cell walls
contained an unusually high level of galacturonic acid (4).
The chemical compositions of commercial A. vera products
have been reported by several authors. One study examined
nine commercial A. vera gel powders to assess the quality
and authenticity by the analysis of acetylated polysaccharides,
free sugar, and organic acid profiles (19). Another work used
the 1
H-NMR spectrometry method to inspect five major aloe
markers—acetylated polysaccharides, glucose, malic acid, lactic
acid, and acetic acid—in 18 A. vera commercial products (21).
Despite the number of studies that have been published, an
integrated chemical composition analysis for aloe products has
been lacking. It would be helpful to know the major components
for the evaluation of the quality of aloe products. Because minor
constituents like anthroquinones must be removed during the
manufacturing process, the aim of the present work is to carry
out only major constituent characterization and quantitation.
Experimental
Fresh Aloe Leaves and Commercial Aloe Samples
Fresh aloe leaves were collected from Yunnan, China, and
Tamaulipas, Mexico, and used in the current study. Both sources
of aloe leaves were identified as A. vera by DNA barcoding
analysis. The aloe leaves collected from China were first cleaned
by water, and the leaf tip, butt, barbs, and edges were removed
using a knife. The whole aloe leaf sample was made by grinding
entire aloe leaves in a high-speed blender until the blend was
flowing smoothly and no large chunks remained. The blend was
then lyophilized to yield sample 1. The gel and rind samples were
prepared by filleting the cleaned leaves with a knife to separate
the rind (skin) from the inner leaf (gel). The rind and gel were
thoroughly washed with distilled water to remove any leftover
latex on the leaves and lyophilized to give gel powder 2 and rind 3.
The leaves collected from Mexico were prepared into four parts.
The butt and tip of the leaf plus barbs from the edges of the leaf
were trimmed with knife. The leaf was ground in a blender until
the blend was flowing smoothly and no large chunks remained.
The contents of the blender were extruded through a 4-ply bedding
of cheesecloth and the soluble portion was lyophilized to give
whole leaf juice powder 4. The inner leaf was filleted from the
Downloaded
from
by
guest
on
18
June
2023

rind and was ground in the blender until no chunks remained and
the contents were flowing smoothly. The blend was centrifuged
at 4000 rpm for 5 min and the supernatant was transferred and
lyophilized along with the washings of the insoluble fraction to
give soluble gel 5a. The insoluble residue was rinsed with water
two times (the washings added to the soluble fraction as indicated
above) and lyophilized to produce gel insoluble sample 5b. The
rind was rinsed under water to remove any remaining inner gel
plus as much of the vascular component as possible and was then
diced into small cubes and lyophilized to give sample 6. Samples
1–3 were freeze-dried using a SCIENTZ-12N lyophilizer.
Samples 4–6 were freeze-dried on a Virtis Genesis 35-L pilot
lyophilizer. Commercial aloe powders were acquired from three
aloe manufacturers and were identified to be made from A. vera
by comparing their chemical profiles with authentic specimen.
The description for all the tested samples is given in Table 1.
Reagents
The organic acid standards, malic acid (99.9% pure) and citric
acid (99.9%), were purchased from Supelco (Bellefonte, PA).
Acetic acid, isocitric acid trisodium salt hydrate (≥97%), and
isocitric acid lactone (97%) were purchased from Sigma-Aldrich
(St. Louis, MO). Fumaric acid (99.0%) was purchased from
Aladdin (Shanghai, China). Lactic acid (91.2%) was purchased
from Dr. Ehrenstorfer Gmbh (Augsburg, Germany). Oxalic acid
(≥99.5%),tartaricacid(≥99.5%),formicacid(≥98%),andsuccinic
acid (≥99.5%) were from Sinopharm Reagents (Sinopharm,
Shanghai, China). Narrow pullulans (MW 10.0, 21.7, 48.8, 113,
200, 366, and 805 kDa) and broad dextrans (MW50, 80, 150, 410,
670, and 1500–2800 kDa) were purchased from Sigma (Sigma-
Aldrich) and used as testing standards for MALS recovery
measurement. Each standard was dissolved in 0.1 M NaCl to
make concentrations of 125, 250, 500, and 1000 μg/mL and were
filtered through 0.45μm Xiboshi mixed cellulose esters (MCE)
syringe filter (Tianjin Fuji Science and Technology Co., Tianjin,
China) before injection. HPLC grade acetonitrile was purchased
from Merck (Darmstadt, Germany). ELGA PURELAB®
water
(Veolia Water Solution & Technologies, High Wycombe, United
Kingdom) was used during the entire experiment for sample and
standard preparations and chromatographic mobile phase.
Moisture
Moisture content was determined by drying the sample
in a forced convection oven at 105°C to a constant weight
(GB 5009.3–2010 Determination of Moisture in Foods; 25).
Total Ash
Total ash content was determined by the ignition method. The
sample was charred first and then placed in a muffle furnace
at 550°C and dried to a constant weight according to AOAC
INTERNATIONAL, 2012, Method 923.03 (26).
Lipid Analysis
Lipid content was measured by extracting the samples with
hexane in a Soxhlet assembly following the procedure of
AOAC, 2012, Method 2003.06 (27).
Protein Analysis
Protein content was determined based on the amount of
nitrogen that was obtained by Tecator Kjeltec 8400 Analyzer
(FOSS Analytical A/S, Hillerod, Denmark) and then converted
to protein by multiplying the nitrogen content by 6.25 (AOAC,
2012, Method 2001.11; 28).
Fiber Analysis
The dry sample was digested with 1.25% H2SO4 under
boiling for 30 min and then filtered through 300 mesh nylon net
(Jufeng Screen, Dongguan, Guangdong, China), followed by
washing with boiling water until pH 7 was reached. The residue
was digested with 1.25% NaOH under boiling for 30 min,
filtered through 300 mesh nylon net, and washed sequentially
with boiling water, ethanol, and ether, respectively. The residue
was placed in a crucible and dried at 105 ± 2°C to a constant
weight. The crucible was then placed in a muffle furnace at
550°C for several hours until all the carbonaceous matter was
burnt off. The ash was weighed after the sample was cooled.
The crude fiber content was the weight of the difference between
the residue and ash (GB/T 5009.10-2003 Determination of
Crude Fiber in Vegetable Foods; 29).
Mineral Elements
Calcium (Ca), magnesium (Mg), potassium (K), sodium (Na),
and phosphorus (P) were measured using inductively coupled
plasma-optical emission spectroscopy (ICP-OES; iCAP 6300
Table 1. A. vera fresh leaf and commercial samples
analyzed
Sample
a
Aloe plants/products Process
b
1 Whole leaf FD
2 Inner leaf (gel) FD
3 Rind FD
4 Whole leaf juice FD
5a Inner leaf soluble gel FD
5b Inner leaf insoluble gel FD
6 Rind FD
7 Gel (200:1) SD
8 Gel (200:1) SD
9 Gel (200:1) FD
10 Whole leaf (100:1) FD
11 Whole leaf (100:1) FD
12 Whole leaf (100:1) SD
13 Gel (200:1) SD
14 Gel (200:1) SD
15 Whole leaf extract EP/FD
16 Inner leaf extract EP/FD
17 Whole leaf extract EP/FD
18 Inner leaf extract EP/FD
a

1–3: Fresh leaf from Yunnan, China; 4–6: fresh leaf from Tamaulipas,
Mexico; 7–11: from company A; 12–14: from company B; 15–18: from
company C.
b
FD=Freeze dried; SD=Spray dried; and EP=Ethanol precipitation.
Downloaded
from
by
guest
on
18
June
2023

solution was gently shaken to mix well, filtered through 0.45 μm
membrane filters, and stored in a refrigerator at 4°C before
injection. For rind samples, an extra step of extraction at 60°C in
a water bath for 1 h was included. The MW of polysaccharides
and quantitation were analyzed on an SEC system consisting
of a Waters 2695 separation module, a Waters 2414 differential
refractive index (dRI) detector (Waters Co.), and a DAWN-
HELEOS-II MALS detector (Wyatt Technology, Santa Barbara,
CA). The system set up was SEC-MALS-RI in series. The
polysaccharide solutions were separated on a Phenomenex
PolySep-GFC-P Linear column (7.8 × 300 mm) with a TSKgel
PWXL guard column (40 × 6 mm, 13 μm) in isocratic elution
using 0.1 M NaCl as mobile phase, which was filtered through an
inline 0.10 μm × 25 mm Durapore membrane filter (Millipore Co.,
Bedford, MA). The temperature of the column and RI detector
were operated at 35°C, the flow rate was 0.7 mL/min, and the
injection volume was 100 μL. Data analysis was performed on
ASTRAVersion 6.1.5 Software (Wyatt Technology) utilizing the
Zimm formalism and RI increment (dn/dc) of 0.14 mL/g.
Results and Discussion
Overall Chemical Composition
Three fractions of fresh Aloe vera plant from China (Figure 1a)
and four fractions from Mexico (Figure 1b) were prepared and
analyzed. In general, the matured aloe leaf plant is composed of
approximately 55–70% inner leaf and 30–45% rind by weight.
The inner leaf contains about 98.5–99.5% water and 0.5–1.5%
solids; the rind contains 88–91% water and 9–12% solids. The
whole leaf contains total solids of about 3.5-4.5%, while the
extractable solid of the whole leaf was approximately 1%.
The dry weight of the inner leaf soluble fraction to the insoluble
fraction is about 2:1 to 3:1. In the commercial aloe products
analyzed,accordingtotheinformationprovidedbymanufacturers,
the products comprised aloe juice powder manufactured
from different plant parts (i.e., whole leaf or inner gel)
and the products were made from different processes (i.e.,
ethanol precipitated or non-ethanol precipitated). Products made
from whole leaf are typically termed 100:1, meaning 100 parts
of whole leaf juice to make 1 part of juice powder. The inner gel
is called 200:1, meaning 200 parts of inner gel to make 1 part
of powder, considering 0.5% extractive solid from this source.
The main components in these analyzed samples were found
to be the ash, free sugars, organic acids, and polysaccharides.
The protein contents are relatively high in fresh plants, in the
range of 3.8–8.3%, and higher in rind than in gel. Protein content
is low in the juice powders, assuming proteins were removed in
the filtering and decolorization process. High protein contents
were found in the four ethanol-precipitated products (samples
15–18) because the proteins were insoluble in ethanol and
were precipitated out together with polysaccharides. The lipid
content of the ethanol-precipitated products was in the range
of 2.2–4.3% but was found to be less than 1% in commercial
juice powders. The reduction was most likely due to the non-
water-soluble lipids being removed by filtration during aloe
manufacturing process. Total ash and organic acids represent
major parts of the entire compositions, accounting for 33–58%
in most analyzed samples. Free sugars took another major part,
in the range of 6.9–37.7% of the total weight, except for the
ethanol-precipitated products, which contained only 0.1–0.2%.
This is because the free sugars are readily dissolved in the
Series, Thermo Scientific, Sunnyvale, CA) according to the
AOAC, 2012, Method 993.14 procedure (30).
Free Sugar Analysis
About 25.0 mg of dry powder was dissolved in 100 mL of
water and sonicated at room temperature for 30 min to extract
sugars.Theextractwasfilteredthrough0.45μmhydrophilicPTFE
membranefilters(XiboshiSyringeFilter,TianjinFujiScienceand
Technology Co.) and stored in refrigerator at 4°C before analysis.
Standardstocksolutionwaspreparedbyweighingabout100.0mg
of glucose, 50.0 mg of fructose, and 30.0 mg of sucrose,
mixing, and dissolving in 100 mL of ultrapure water as stock
solution, and storing in a refrigerator at 4°C before analysis.
The standard calibration solutions were prepared by diluting
the stock solution according to the factors of 10:1, 25:1, 50:1,
100:1, 250:1, and 500:1 for establishing standard curves. The
sugar analysis was carried out with Dionex high performance
anion exchange chromatography (HPAEC) equipped with pulsed
amperometric detection (PAD; Thermo Scientific). Glucose,
fructose, and sucrose were separated on a Dionex CarboPac PA10
(250 × 4 mm) chromatography column with a Dionex CarboPac
PA10 (50 × 4 mm) guard column. The solvent system was
35 mM sodium hydroxide and was run in isocratic conditions
with a flow rate of 1.0 mL/min. Both the column and detector
temperature were operated at 35°C. The injection volume was
25 μL, and data analysis was performed on Dionex Chromeleon
version 7.2.3.7553 software (Thermo Scientific).
Organic Acid Analysis
The samples were prepared by accurately weighing about
250.0 mg of powder into 50 mL of volumetric flask and mixing
with about 40 mL of water. The solution was sonicated at room
temperature for 30 min. The extract was allowed to cool to room
temperature before the final volume was brought to 50 mLand was
then filtered through a 0.45 μm hydrophilic PTFE membrane filter
before the HPLC injection. The mixed organic acid standards were
dissolved in ultrapure water, and stock solution was prepared at the
concentrations of fumaric acid, 10 mg/L; oxalic acid, 200 mg/L;
tartaric and formic acids, 1000 mg/L each; malic acid 5000 mg/L;
isocitric, lactic, acetic, citric, and succinic acids, 2500 mg/L
each; and isocitric acid lactone, 2500 mg/L. The stock solution was
further diluted by the factors of 1:1, 5:1, 10:1, 25:1, 50:1, 250:1,
500:1, and 1,000:1 for standard curves. Standard solutions were
stored at 4°C before analysis. HPLC was performed on a Waters
2695 separation module and a Waters 2998 photodiode array
detector (Waters Co., Milford, MA) with a Phenomenex Luna C18
(5 μm, 250 × 4.6 mm) column and aThermoAcclaimTM
OA(5 μm,
250 × 4.6 mm) column connected in series. The mobile phase was
0.2% phosphoric acid–acetonitrile (98 + 2), and chromatography
was run in isocratic elution mode. The column temperature was
operatedat20°C,theflowratewas0.4mL/min,theinjectionvolume
was 25 μL, and the detection wavelength was set at 210 nm. Data
analysis was performed with Empower 3.0 Software (Waters Co.).
MW of Polysaccharides and Quantitative Analysis
Polysaccharide sample solutions were prepared by accurately
weighing about 50.0 mg of powder and dissolving in 50 mL of
0.1 M NaCl solution at room temperature for 20–24 h.The sample
Downloaded
from
by
guest
on
18
June
2023

andKarepredominantinmostofthetestedsamples,accountingfor
67–91% of the five. Distribution of the minerals in gel and rind are
quitesimilar.Thetotalofthefiveminerals,exceptforinsample16,
were in the range of 6.3–13.5% and their corresponding total
ash contents were approximately double this quantity. Analysis
of the ash samples from the commercial aloe products by ICP-
OES indicated that the five minerals are still the major mineral
elements in the ash. The increased weight of the ash is due to
the formation of the mineral complex in combustion during ash
analysis, as KCl, CaCO3, CaMg(CO3)2, and so on were observed
by X-ray diffraction analysis of the ash samples (data not shown).
The mineral elements had historically been used as key parameters
by the aloe industry for quality control (31).
Organic Acids Analysis
The concentration of organic acids was measured by an in-
house developed method, which is a reversed-phase HPLC
method using two C-18 columns connected in series for full
separation and quantitation of aloe organic acids, including
oxalic, malic, isocitric, lactic, citric, fumaric, and isocitric acid
lactone, that have been reported in A. vera products made from
either whole leaf or inner leaf (Figure 2A–2D; 19). The results
of organic acids in the fresh and commercial aloe powders are
given in Table 4.
A total of eight organic acids were detected in the current
method, and their quantities were determined through
comparison with individual standards. Except for sample 16,
the sum of the total acids was in the range of 14.9–31.4%, and
malic acid has the highest concentration among these acids. It
has been reported that a high content of malic acid is typically
found in succulents, as it plays an important role in fixing carbon
dioxide during the night through crassulacean acid metabolism.
Plants utilize carbon dioxide in photosynthesis during the
daytime. Therefore, diurnal fluctuation of malic acid content
75–85% ethanol, which is the commonly used ethanol
concentration to make ethanol–precipitation products. Sample
16 contains low ash (6.7%) and organic acids (5.9%), but its
polysaccharide content is the highest among all the tested
samples, reaching to 40%, which is likely due to extensive
purification, with the ethanol precipitation removing more
minerals and organic acids while enriching polysaccharide
content. High fiber contents were found in whole leaf sample 1
and rind 3 and 6, which suggest that a significant amount of leaf
tissue structure was not removed during sample preparation. In
contrast to sample 1, only juice was obtained from the whole
leaf for sample 4, which used the same procedure of making
aloe leaf juice product, and very low fiber content was detected.
High fiber content was determined in inner leaf sample 6, about
21.8%, deriving mainly from the inner gel cell wall. When the
soluble gel 5a was separated the from the insoluble gel 5b,
most fibers remained in insoluble gel (45.8%). The overall
carbohydrate compositions of the fresh leaf obtained from the
present work are close to the published data (4).
That the water-insoluble fibers are removed by filtration in
typical aloe manufacturing processing was confirmed by only
trace amounts of fiber content being detected in commercial
aloe juice powder samples 7–14, whereas considerable amounts
of fiber were seen in the ethanol-precipitated samples 15–18.
As fibers do not dissolve in ethanol, they are not able to be
separated from other ethanol-precipitated substances like poly
saccharides. The analyses on the major components of A. vera
presented above allowed 85–95% of the total composition to be
determined, and the results are shown in Table 2.
Major Mineral Analysis
Mineral analysis of the samples showed that the Ca, K, Mg,
Na, and P were the major minerals in both the fresh aloe leaves
and commercial samples (Table 3). Among the five elements, Ca
A. vera fresh leaves from China A. vera fresh leaves from Mexico
Trim
(a) (b)
Trim
Leaves 1kg, 3.7% solids
Filet
Rind 335g,
9.8% solids
Gel 630g,
0.9% solids
Grind
Lyophilize
Rind powder
33g, 3
Gel powder
5.7g, 2
Whole leaf
powder
22g, 1
Grind
Lyophilize
Leaves 0.6kg Leaves 5.6kg Leaves 3.9kg
Fileted Grind
Centrifuge
Lyophilize
Whole leaf
powder
26.9g, 4
Gel
Grind, centrifuge
Lyophilize
Gel insoluble
7.6g, 5b
Gel soluble
22.7g, 5a
Rind powder
220g, 6
Cut
Lyophilize
Figure 1. Preparation of aloe juice powders from different A. vera plant parts (a) from Yunnan, China, and (b) from Tamaulipas, Mexico.
Downloaded
from
by
guest
on
18
June
2023

has been observed in aloe plants (32). The fresh whole aloe leaf
contained malic, citric, and isocitric acids and a small amount
of isocitric acid lactone in the concentrations of 10.6, 2.8, 5.8,
and 0.61%, respectively, while filleted inner leaf contained
malic acid (22.7%) as the only major acid. Malic, isocitric, and
citric acids and isocitric acid lactone were found to be the major
Table 2. Major chemical composition of A. vera samples (g/100g on dry basis)
Sample LOD
a
Ash Fiber Protein Lipids
Organic
acids
Free
sugars
Polysacch-
arides Sum
b
1 5.7 14.9 23.8 7.7 2.2 19.9 11.3 8.8 86.9
2 5.2 16.0 18.8 4.7 2.7 22.8 18.1 8.1 88.4
3 6.0 14.1 27.5 8.3 2.2 19.8 6.9 9.3 86.6
4 5.1 28.6 1.2 4.5 4.3 29.6 21.8 8.1 88.1
5a 6.4 28.8 4.5 3.8 4.2 25.6 22.5 11 92.5
5b 6.8 12.9 45.8 3.8 3.8 8.7 6.6 6.9 88.7
6 5.3 16.8 21.8 5.0 3.9 22.9 7.1 10.4 84.6
7 6.2 16.2 tr
c
1.2 0.45 24.7 37.7 8.3 85.7
8 3.3 16.5 tr 1.2 0.32 27.0 34.8 12.5 87.5
9 7.0 15.3 tr 0.9 0.28 27.0 37.7 7.1 87.2
10 5.9 18.1 tr 1.1 0.34 31.4 34.5 7.5 89.4
11 2.6 14.8 tr 0.7 0.50 22.4 37.7 15.4 86.8
12 2.9 20.8 tr 1.8 0.55 27.1 29.6 16.1 88.0
13 5.2 27.7 tr 2.0 0.43 22.6 30.7 11.8 86.1
14 2.6 24.1 tr 2.8 0.21 28.0 31.2 12.2 89.0
15 8.0 21.6 7.3 4.6 2.9 26.4 0.1 33.6 90.4
16 5.3 6.7 22.6 8.8 2.4 5.9 0.2 45.4 94.4
17 5.2 14.6 36.7 9.8 3.7 14.9 0.1 14.2 90.9
18 5.7 16.8 29.8 7.4 2.0 18.9 0.1 21.7 95.1
a
LOD=Loss on dry.
b
Sum of LOD, fibers, proteins, lipids, organic acids, free sugars, and polysaccharides, plus five major minerals. Ash contents are not included.
c
tr=Trace.
Table 3. Concentration of major minerals in A. vera leaf
and commercial samples (g/100g on dry basis)
Sample Ca K Mg Na P Sum Ash
1 2.8 3.7 0.6 0.3 0.1 7.5 14.9
2 2.5 4.3 0.6 0.4 0.2 8.0 16.0
3 2.3 3.7 0.5 0.2 0.1 6.7 14.1
4 4.5 5.8 0.8 2.1 0.3 13.5 28.6
5a 4.4 6.9 0.8 2.2 0.2 14.5 28.8
5b 2.9 2.1 0.3 0.8 0.1 6.3 12.9
6 4.3 2.4 0.6 0.8 0.2 8.2 16.8
7 4.3 0.8 1.4 0.3 0.4 7.2 16.1
8 5.1 1.2 1.1 0.4 0.8 8.4 16.5
9 4.4 0.4 1.6 0.1 0.6 7.2 15.3
10 5.3 1.3 1.6 0.3 0.3 8.7 18.1
11 5.0 0.4 1.4 0.5 0.4 7.5 14.8
12 2.7 5.2 1.0 0.5 0.5 10.0 20.8
13 3.1 7.4 1.3 1.3 0.2 13.3 27.7
14 2.9 7.3 1.2 0.5 0.2 12.1 24.1
15 6.0 0.4 0.2 0.8 0.2 7.6 21.6
16 2.4 0.3 0.1 0.7 0.3 3.8 6.7
17 4.1 1.4 0.5 0.2 0.1 6.3 14.6
18 7.1 1.7 0.5 0.1 0.3 9.7 16.8
Figure 2. HPLC chromatograms of (A) organic acid standards;
(B) whole leaf juice powder (sample 1); (C) gel juice powder
(sample 2); and (D) rind (sample 3). Peak 1 = oxalic acid; peak
2 = tartaric acid; peak 3 = formic acid; peak 4 = L-malic acid; peak
5 = isocitric acid; peak 6 = lactic acid; peak 7 = acetic acid; peak
8 = isocitric acid lactone; peak 9 = citric acid; peak 10 = succinic acid;
and peak 11 = fumaric acid.
Downloaded
from
by
guest
on
18
June
2023

of freshness of aloe leaf (35). It is suggested that aloe leaves be
processed as quickly as possible after harvesting to minimize any
enzymatic reactions. A trace amount of acetic acid was detected
in two aloe samples, 7 and 9. It is generally agreed that acetic
acid is derived from the aloe acetylated polysaccharides, which
can be a sign of degraded acetylated polysaccharides in aloe
products. However, it is difficult to correlate acetic acid content
to the quality of aloe product because the amount of acetic acid
is reduced during the aloe manufacturing process through the
heating and solvent evaporation processing steps.
Free Sugars Analysis
Free sugars in the aloe samples were measured by HPAEC-
PAD and the results are given in Figure 3A–3D and Table 5. Three
sugars, including glucose, fructose, and sucrose, were detected in
organic acids in the rind, with the concentrations of 7.4, 7.8, 3.8,
and 0.73%, respectively. Literature reported that a high amount
of isocitrate was shown in aloe green tissue (rind), while it was
lacking in the water tissue (inner leaf), where malate was the
dominant acid (33). Therefore, isocitric acid and isocitric acid
lactone have been used as marker compounds to distinguish aloe
gel from whole leaf in quality control by the aloe industry (5).
Although citric acid is not detected in gel, it is commonly used
as a flavor or pH adjustment agent in the food industry, which
makes it lack uniqueness as a marker for aloe identification.
All the tested whole leaf juice powders (samples 10–12, 15,
and 17) were found to contain high amount of isocitric acid.
In commercial aloe gel samples, trace amounts of isocitric acid
were still detected, which is supposed to be from the rind, as
gel and rind usually cannot be separated cleanly in large scale
production. In the aloe industry, ethanol-precipitated products are
made by treating aloe juice with aqueous ethanol. The high-MW
polysaccharides are not soluble in ethanol and precipitate from
the ethanol solution, where small molecules remain dissolved.
Theoretically, small molecule organic acids should be removed
by ethanol treatment, but a considerable amount of organic acids,
however, can still be seen in the ethanol-precipitated samples,
which might be due to the existing complex of polymers and
organic acids or ester bond of organic acid with polysaccharides.
For example, one paper reported the isolation of maloyl glucans
from A. vera gel, in which the malic acid was attached at each of
the C-6 hydroxyl group of a glucan (34).
Samples 7–14 contained a small amount of lactic acid, ranging
from 0.11 to 4.0%, while it was undetected in samples 1–6 made
fromthefreshaloeleaf.Researchhasindicatedthatthelacticacidis
produced from malic acid by lactic acid bacteria. The reduction of
the malic acid content and increase of lactic acid can be indicators
Figure 3. HPAEC-PAD chromatogram of (A) standards of free
sugars; (B) whole leaf (sample 1); (C) gel (sample 2); and (D) rind
(sample 3). Peak 1 = glucose; peak 2 = fructose; and peak 3 = sucrose.
Table 4. Concentration of organic acids in A. vera leaf and commercial samples (g/100g on dry basis)
Sample Oxalic L-Malic Isocitric Lactic Acetic
Isocitric acid
lactone Citric Fumaric Sum
1 0.13 10.56 5.79 NDa
ND 0.61 2.81 ND 19.90
2 0.07 22.73 ND ND ND ND ND ND 22.80
3 0.18 7.37 7.82 ND ND 0.73 3.69 ND 19.79
4 0.04 17.64 7.42 0.24 0.92 1.22 1.85 0.01 29.57
5a 0.03 22.40 0.82 0.22 0.05 0.17 1.79 0.01 25.63
5b 0.03 6.85 0.40 0.24 0.00 0.10 0.87 ND 8.66
6 0.04 6.34 11.66 0.13 1.10 2.14 1.40 ND 22.94
7 0.02 18.98 0.43 3.35 0.05 0.07 1.73 0.02 24.65
8 0.01 20.30 0.12 3.98 ND ND 2.59 0.01 27.01
9 0.02 22.70 0.43 2.10 0.07 ND 1.63 0.03 26.98
10 0.02 19.92 4.66 1.41 ND 0.90 4.42 0.04 31.37
11 0.01 12.83 2.57 2.89 ND 0.80 3.30 0.01 22.41
12 0.02 14.52 5.78 3.00 ND 1.15 2.64 0.01 27.12
13 0.01 20.94 1.01 0.11 ND 0.24 0.24 0.06 22.61
14 0.01 26.82 0.51 0.22 ND 0.11 0.24 0.05 27.96
15 0.03 7.33 11.39 ND ND ND 7.63 ND 26.38
16 0.07 4.01 ND ND ND 1.31 0.51 ND 5.90
17 0.06 5.69 5.23 ND ND 0.78 3.11 ND 14.87
18 0.07 15.95 0.37 ND ND 2.11 0.39 ND 18.89
a
ND=Not detected.
Downloaded
from
by
guest
on
18
June
2023

through the ethanol-precipitation process, were found to contain
very low amounts of free sugars, which can be understood
because free sugars are soluble in the aqueous ethanol and were
removed during the manufacturing process.
Polysaccharides Analysis
MWs and content of polysaccharides were determined
using SEC-MALS-dRI detectors, and the results are given in
Figure 4 and Table 6. The MW of tested polysaccharides by
MALS measurement is the weight-average molecular weight,
Mw. The resulting Mw found in fresh leaf samples 1–6 were
around 567–2613 kDa, corresponding to the result of 1200 kDa
from fresh leaf by MALS reported in literature (39). Decreased
polysaccharide MW was observed if the fresh leaf was
the commercial aloe juice powders. Glucose and fructose, but not
sucrose, were detected in the gel made from fresh leaf. In most
tested samples, glucose is predominant, with a ratio of glucose
to fructose of around 2:1 to 4:1. With respect to leaf parts, the
amount of glucose in gel is about 3 times of that in rind. High
glucose and fructose content, in the range of 22–26 and 5–12%,
respectively, were found in the commercial aloe juice products
(samples 7–14) verses 4–14 and 2–4%, respectively, found in
the original fresh leaf (samples 1–6). It cannot be determined if
the increasing amounts of glucose and fructose were generated
during the manufacturing process because of degradation of
plant polysaccharides, the use of the enzymes such as cellulase
for reducing the viscosity of viscous aloe juice, or the use as
additives to adjust taste. No detailed information was provided
by manufacturers. The increasing amount of fructose could be
the breakdown product of fructose polymer, as fructans have been
reported to be isolated from A. vera (36). Aloe leaf was reported
to contain eight enzymes, including cellulase (37), which is
responsibleforbreakingdowncellulosiccellwalls.Harvestedfresh
aloe leaf must be processed within a short period of time to avoid
degradation of polysaccharides by these endogenous enzymes.
Different MWs of polysaccharides were found in all the tested
samples, suggesting polysaccharide degradation occurs during
manufacturing. However, no mannose was detected in any of the
samples containing either higher- or lower-MW polysaccharides,
indicating that the breakdown of the polysaccharides might occur
between the glycosidic bonds of glucoses. In one patent, it was
believed by the authors that acemannans were connected to each
other, forming block polymer through mainly glucose-composed
oligosaccharides. Endogenous β-1, 4 glycosidases began to break
the linkage of the block polymer to liberate acemannan after aloe
leaf was harvested (38). More studies are needed to understand
structures of polysaccharides. The samples 15–18, manufactured
Table 5. Concentration of free sugars in A. vera leaf and
commercial samples (g/100g on dry basis)
Sample Glucose Fructose Sucrose Sum
1 8.0 3.3 NDa
11.3
2 14.2 3.9 ND 18.1
3 4.6 2.3 0.06 6.9
4 16.6 5.0 0.16 21.8
5a 18.8 3.7 0.00 22.5
5b 5.3 1.3 0.00 6.6
6 3.9 1.5 1.66 7.1
7 26.2 11.1 0.38 37.7
8 23.4 10.9 0.56 34.8
9 25.2 12.1 0.46 37.7
10 23.0 8.0 3.51 34.5
11 23.7 9.4 4.60 37.7
12 22.1 5.4 2.09 29.6
13 23.9 6.8 0.07 30.7
14 23.8 7.2 0.13 31.2
15 0.04 0.02 0.01 0.07
16 0.14 0.03 ND 0.17
17 0.05 0.02 0.02 0.09
18 0.10 0.02 ND 0.12
a
ND=Not detected.
Figure 4. GPC-MALS-dRI chromatograms of whole leaf (red trace),
inner leaf (green trace), and rind (blue trace).
Table 6. Weight-average MW (Mw), number-average MW
(Mn), and polydispersity (PD) by MALS measurement, and
concentration of polysaccharides (g/100g on dry basis), in
A. vera leaf and commercial samples
Sample Mw, kDa Mn, kDa PD
a
Polysaccharides, %
1 567 302 1.9 8.8
2 1101 782 1.4 8.1
3 937 459 2.0 9.3
4 1191 870 1.4 8.1
5a 2613 2329 1.1 11.0
5b 2144 1845 1.2 6.9
6 856 444 1.8 10.4
7 19 16 1.2 8.3
8 22 19 1.2 12.5
9 28 19 1.5 7.1
10 237 49 4.9 7.5
11 23 20 1.2 15.4
12 194 78 2.5 12.2
13 126 88 1.4 11.8
14 136 73 1.9 12.2
15 947 544 1.7 33.6
16 1591 1196 1.3 45.4
17 2641 2511 1.1 14.2
18 1944 1615 1.2 21.7
a
PD=Mw/Mn.
Downloaded
from
by
guest
on
18
June
2023

In the present study, quantitation of the polysaccharides
was achieved by mass recovery data obtained from SEC-
MALS-dRI. The accuracy of quantitation was confirmed
by injecting various known concentrations of pullulan
and dextran standards. The recovery data are calculated
by dividing the resulting concentration obtained from the
dRI detector over the injected mass, and the results are
given in Table 7. Recoveries are 92–102 and 84–101% for
pullulan and dextran, respectively. Quantitative results of
all the aloe polysaccharides are shown in Table 6. In fresh
leaves, they are in the range of 8.1–11.0%. There are about
6.9% polysaccharides in the insoluble inner gel, which
is likely from the residues of inner leaf gel because of the
difficulty of exhaustively extracting the polysaccharides from
the insoluble gel. Polysaccharides found in non-ethanol-
precipitated samples are in the range of 7.1–16.1%, while they
are higher in the ethanol-precipitated samples, in the range
of 14.2–45.4%, and especially high in samples 15 and 16.
Polysaccharides are generally dissolved in water and
precipitated in the presence of ethanol. When the ethanol
concentration increases, more polysaccharides are precipitated
because ethanol reduces the polarity of the solution. Once
ethanol concentration reaches about 80%, free sugars and
other small molecules still dissolve in the solution, while
the solubility of polysaccharides is poor. The polysaccharide
purities are enriched through filtration or centrifugation to
separate them from small molecules. It needs to be pointed
out that the polysaccharide concentration determined by SEC-
MALS-dRI is different from that determined by 1
H-NMR,
not processed timely, e.g., within hours (data not shown).
Endogenous or exogenous organisms of aloe can degrade
polysaccharides (40). Polysaccharides extracted from inner
leaf contained high Mw of 2613 kDa in sample 5a compared
with that from rind (856 kDa) in sample 6. The four samples,
15–18, made from ethanol precipitation keep the high Mw with
less degradation on the structure of polysaccharides, as ethanol
deactivated the enzymes that may potentially hydrolyze the
polysaccharides, and the time and condition to dehydrate the
precipitated polysaccharides were much shorter and milder
than those of the non-ethanol-precipitation process. In the non-
ethanol-precipitation conditions, the whole aloe leaf or inner leaf
was ground and pressed to release the juice. The juice usually
contains only 0.5–1.5% solids, and a significant amount of water
needs to be removed by evaporation.The MWof polysaccharides
underwent a certain degree of degradation in processes such as
heat. In addition, external enzymes, such as cellulase, are used in
some manufacturing processes to facilitate the extraction of the
gel from the leaf (40, 41), and the enzymatic treatment results
in the reduction of the polysaccharide MW (42, 43). In the non-
ethanol-precipitated products, the results of Mw measurement
were markedly lower (19–237 kDa) than in ethanol-precipitated
products, with Mw 947–2641 kDa. The commercial samples
tested herein are from three different aloe product manufacturers,
and even though no detailed manufacturing processes are
provided by these manufacturers, the results clearly demonstrate
that aloe products are manufacturing-process dependent and
the MW of the resulting aloe polysaccharides do vary among
different manufacturers and different manufacturing processes.
Table 7. Weight-average MW (Mw) and recovery of pullulans and dextrans by MALS measurement
Pullulan Dextran
Mw, kDa
Injected
mass, μg
Calc.
mass, μg
Mass
rec., % Mw, kDa
Injected
mass, μg
Calc.
mass, μg
Mass
rec., %
10 25 23.2 92.7 50 25 21.9 87.0
50 46.5 93.0 50 42.3 84.6
100 93.8 93.8 100 91.2 91.2
21.7 25 24.2 96.9 80 25 23.2 92.8
50 48.3 96.7 50 46.8 93.6
100 97.2 97.2 100 93.0 93.0
48.8 25 23.2 92.7 150 25 23.7 94.8
50 47.1 94.1 50 46.8 93.6
100 95.8 95.8 100 94.6 94.6
113 25 24.4 97.6 270 25 24.8 99.3
50 47.9 95.8 50 49.6 99.1
100 95.2 95.2 100 98.2 98.2
200 25 24.4 97.5 410 25 25.2 100.9
50 48.3 96.5 50 48.9 97.7
100 97.6 97.6 100 96.1 96.1
366 25 25.5 101.9 670 25 25.1 100.5
50 49.9 99.8 50 50.4 100.7
100 97.6 97.6 100 99.4 99.4
805 25 25.6 102.2 1950 25 25.1 100.2
50 50.3 100.6 50 49.4 98.9
100 101.0 101.0 100 97.2 97.2
Downloaded
from
by
guest
on
18
June
2023

References
(1) Grace, O.M., Klopper, R.R., Smith, G.F., Crouch, N.R.,
Figueiredo, E., Rønsted, N., van-Wyk, A.E. (2013) Phytotaxa.
76, 7–14. doi:10.11646/phytotaxa.76.1.2
(2) Sung, C.K. (2006) in New Perspectives on Aloe, Y.I. Park,
S.K. Lee (Eds), Springer Science+Business Media,
New York, NY, pp 7–17
(3) Moghaddasi, M.S., Verma, S.K. (2011) Int. J. Biol. Med. Res.
2, 466–471
(4) Ni, Y., Turner, D., Yates, K.M., Tizard, I. (2004)
Int. Immunopharmacol. 4, 1745–1755. doi:10.1016/j.
intimp.2004.07.006
(5) Jones, K. (2012) in Aloe Vera Leaf, Aloe Vera Leaf Juice, Aloe Vera
Inner Leaf Juice, Aloe vera (L.) Burm. f.: Standards of Identity,
Analysis, and Quality Control, R. Upton P. Axentiev (Eds),
American Herbal Pharmacopeia, Scotts Valley, CA, pp 13–16
(6) Ni, Y., Yates, K.M., Tizard, I.R. (2004) in Aloes: The Genus
Aloe, T. Reynolds (Ed.), CRC Press, Boca Raton, FL, pp 75–87
(7) Dagne, E., Bisrat, D., Viljoen, A., Wyk, B.-E. V.
(2000) Current Organic Chemistry 4, 1055–1078.
doi:10.2174/1385272003375932
(8) Hamman, J.H. (2008) Molecules 13, 1599–1616. doi:10.3390/
molecules13081599
(9) Javed, S., Atta-ur-Rahman (2014) in Studies in Natural
Products Chemistry, Vol. 41, Atta-ur-Rahman (Ed.),
Elsevier B.V., Amsterdam, Netherlands, pp 261–285.
doi:10.1016/B978-0-444-63294-4.00009-7
(10) Reynolds, T. (2004) in Aloes: The Genus Aloe, T. Reynolds
(Ed.), CRC Press, Boca Raton, FL, pp 39–74
(11) Reynolds, T. (1985) Bot. J. Linn. Soc. 90, 157–177.
doi:10.1111/j.1095-8339.1985.tb00377.x
(12) Wu, X., Wan, J., Zhong, J., Ding, W. (2015) Chinese Journal
of Tropical Crops 36, 1542–1550
(13) Eberendu, A.R., Luta, G., Edwards, J.A., Mcanalley, B.H.,
Davis, B., Rodriguez, S., Henry, C.R. (2005) J. AOAC Int. 88,
684–691
(14) Gu, W., Song, H., Wen, X., Wang, Y., Xia, W., Fang, Y.
(2010) Carbohydr. Polym. 80, 115–122. doi:10.1016/j.
carbpol.2009.10.074
(15) Gu, W., Wang, Y., Wu, T., Li, W., Wang, H., Xia, W. (2012)
Carbohydr. Res. 349, 82–85. doi:10.1016/j.carres.2011.11.026
(16) Light Industry Standards of People’s Republic of China (2007)
QB/T 2489 2007, Aloe Products for Raw Food Material, China
Light Industry Press, Beijing, China
(17) Monakhova, Y.B., Randel, G., Diehl, B.W.K. (2016)
J. AOAC Int. 99, 1213–1218. doi:10.5740/jaoacint.16-0020
(18) Diehl, B., Teichmuller, E.E. (1997) SOFW Journal 123,
1015–1018
(19) Bozzi, A., Perrin, C., Austin, S., Vera, F.A. (2007) Food
Chem. 103, 22–30. doi:10.1016/j.foodchem.2006.05.061
(20) Davis, B., Goux, W.J. (2009) J. AOAC Int. 92, 1607–1616
(21) Jiao, P., Jia, Q., Randel, G., Diehl, B., Weaver, S.,
Milligan, G. (2010) J. AOAC Int. 93, 842–847
(22) Edwards, J. (2012) in Aloe Vera Leaf, Aloe Vera Leaf Juice, Aloe
Vera Inner Leaf Juice, Aloe vera (L.) Burm. f.: Standards of Identity,
Analysis, and Quality Control. R. Upton P. Axentiev (Eds),
American Herbal Pharmacopeia, Scotts Valley, CA, pp 33–42
(23) Turner, C.E., Williamson, D.A., Stroud, P.A., Talley, D.J.
(2004) Int. Immunopharmacol. 4, 1727–1737. doi:10.1016/j.
intimp.2004.07.004
(24) Femenia, A., Sánchez, E.S., Simal, S., Rosselló, C.
(1999) Carbohydr. Polym. 39, 109–117. doi:10.1016/S0144-
8617(98)00163-5
(25) National Food Safety Standard (2010) GB 5009.3-2010
Determination of Moisture in Foods, Ministry of Health of
People’s Republic of China, Beijing, China
because the latter measures the amount of acetyl groups that
correspond to acetylated polysaccharides, whereas SEC-
MALS-dRI detection quantitates all the components that are
eluted from the SEC, including the acetylated polysaccharides,
non-acetylated polysaccharides, and proteins, etc. The
quantitative relationship between MALS measurement and
1
H-NMR has not been established in the present study.
Conclusions
In this study, comprehensive investigations on the aloe
chemical constituents were carried out on two sources of fresh
A. vera leaves and several commercial aloe juice powders made
by different manufacturers and different processes. The results
show that fresh A. vera leaf is mainly composed of organic
acids, minerals, proteins, free sugars, polysaccharides, and
insoluble fibers. In the analyzed commercial juice products,
the major constituents in non-ethanol-precipitated products
are organic acids, minerals, free sugars, and polysaccharides,
which account for greater than 90% of the entire composition
determined. As fresh aloe leaf juice contains over 98% water,
the juice preparation process is similar to a water extraction
and all the water-soluble components mentioned above are
extracted, while the water-insoluble substances, such as lipids,
are not favorable for extraction. The majority of phenolic
compounds existing in latex are removed through activated
charcoal absorption and filtration during the manufacturing
process because they are considered to be unwanted
compounds (e.g., anthraquinone aloins). Ethanol precipitation
increases the concentrations of polysaccharides and reduces
the presence of small molecule compounds. The main
components of the ethanol-precipitated products comprise
only organic acids, polysaccharides, minerals, and proteins.
The present work has provided the general composition
of A. vera products. Although the chemistry varies with
different manufacturing processes, the variations of ratios of
the individual components remain consistent for each type
of process. It is always a challenge to obtain accurate MW
and quantity of the polysaccharides. Aloe polysaccharides are
generally believed to be the main bioactive constituents of
the plant and responsible for a number of reported biological
activities and clinical effects. Quality control of aloe products
includes the determination of MW and quantitation of aloe
polysaccharides. It has been demonstrated that SEC-MALS-
dRI is an effective tool for polysaccharide characterization
without the need for actual aloe polysaccharide standards.
Future work will focus on widening the testing scope of the
polysaccharides, especially on the aloe polysaccharides with
high MW and high branching, as well as on the correlations
of the polysaccharide structures and their physical properties
in solutions.
Acknowledgments
We would like to express thanks to Christopher Thompson
and Zhengfei Lu for conducting DNA barcoding analysis.
Thanks also to Sarah Beamer at the University of West Virginia
for lyophilizing many of the aloe samples, and Jaimie Duensing
for preparing many of the samples for lyophilization.Additional
thanks to Jing Lan at Wyatt Technology, China, for technical
support on MALS analysis.
Downloaded
from
by
guest
on
18
June
2023

(26) Official Methods of Analysis (2012) 19th Ed., AOAC
INTERNATIONAL, Gaithersburg, MD, Method 923.03
(29) National Food Safety Standard (2003) GB/T 5009.10-2003
Determination of Crude Fiber in Vegetable Foods, Ministry
of Health of People’s Republic of China, Beijing, China
(31) Pelley, R.P., Wang, Y.-T., Waller, T.A. (1993) SOFW Journal
119, 255–258
(32) Black, C.C., Osmond, C.B. (2003) Photosyn. Res. 76,
329–341. doi:10.1023/A:1024978220193
(33) Kluge, M., Knapp, I., Kramer, D., Schwerdtner, I., Ritter, H.
(1979) Planta 145, 357–363. doi:10.1007/BF00388361
(34) Esua, M.F., Rauwald, J.W. (2006) Carbohydr. Res.
341, 355–364. doi:10.1016/j.carres.2005.11.022
(35) Tungala, A., Ajay, J.Y., Gajula, P.K., Dinesh, J., Deepak, K.J.
(2011) J. Phytol. 3, 01–11
(36) Salinas, C., Handford, M., Pauly, M., Dupree, P., Cardemil, L.
(2016) Plos One. doi:10.1371/journal.pone.0159819
(37) Surjushe, A., Vasani, R., Saple, D.G. (2008) Indian
J. Dermatol. 53, 163–166. doi:10.4103/0019-5154.44785
(38) Strickland, F.M., Pelley, R.P., Kripke, M.L. Cytoprotective
Oligosaccharide from Aloe Preventing Damage to the Skin
Immune System by UV Radiation. U.S. Patent 5, 824, 659A,
October 20, 1998
(39) Campestrini, L.H., Silveira, J.L.M., Duarte, M.E.R.,
Koop, H.S., Noseda, M.D. (2013) Carbohydr. Polym. 94,
511–519. doi:10.1016/j.carbpol.2013.01.020
(40) Waller, T.A., Pelley, R.P., Strickland, F.M. (2004) in Aloes:
The Genus Aloe, T. Reynolds (Ed.), CRC Press, Boca Raton,
FL, pp 139–205
(41) Ramachandra, C.T., Rao, P.S. (2008) Am. J. Agric. Biol. Sci.
3, 502–510. doi:10.3844/ajabssp.2008.502.510
(42) Qiu, Z., Jones, K., Wylie, M., Jia, Q., Orndorff, S. (2000)
Planta Med. 66, 152–156. doi:10.1055/s-2000-11125
(43) Im, S.A., Oh, S.T., Song, S., Kim, M.R., Kim, D.S., Woo, S.S.,
Jo, T.H., Park, Y.I., Lee, C.K. (2005) Int. Immunopharmacol.
5, 271–279. doi:10.1016/j.intimp.2004.09.031
Downloaded
from
by
guest
on
18
June
2023

jaoac1741.pdf

Recommended

Recommended

More Related Content

Similar to jaoac1741.pdf

Similar to jaoac1741.pdf (20)

Recently uploaded

Recently uploaded (20)

jaoac1741.pdf