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Stability of the main Aloe fractions and Aloe-based commercial products under different storage conditions


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Aloe-based household preparations and commercial products are used worldwide as a source of nutraceutical compounds, among which anthraquinones and acemannan are the most known. However, it is reported that improper storage conditions could lead to significant degradation processes, resulting in a low content of active substances. The aim of this work was to study the stability of aloin and β-polysaccharides in aloe-based products during storage, as a function of temperature and chemical agents added. Generally, aloin degradation in whole leaf homogenate was fast, and neither ascorbate nor the antimicrobial agents could increase stability; a lower temperature slightly improved stability, (DT50 up to 26 days at +4 °C). Regarding the stability of β-polysaccharides, a strong influence of the storage temperature was observed, while antimicrobial agents did not show significant reduction of degradation. For both compounds, household and commercial products were significantly more stable.
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Stability of the main Aloe fractions and Aloe-based commercial
products under different storage conditions
Institute of Environmental and Agricultural Chemistry, Università Cattolica del Sacro Cuore, via Emilia
Parmense, 84, 29122 Piacenza, Italy
Keywords: Anthraquinones, antimicrobial agents, antioxidant agents, degrada-
tion, nutraceuticals, β-polysaccharides
I. – Aloe barbadensis Miller (Aloe vera L.) and Aloe
arborescens Miller are members of the Liliaceae family which are
widely used as source of functional foods, for the application of health
drinks and for pharmaceutical and cosmetic purposes (G and
C-V, 2006; R and S R, 2008).
Many studied have reported that biological activity of Aloe includes pro-
motion of wound healing, antidiabetic, antimicrobial, immunomodulatory,
antioxidant and gastroprotective properties (L and C,
2001; H 2008). Some characteristic polysaccharides seem to pos-
sess the most of pharmacological and physiological properties besides a
synergic action between different components is reported by other authors
(R and S R, 2008; L, 1978). Among these
further active compounds, hydroxyanthraquinones are the most important.
Among polysaccharides, some acetylated mannans, namely aceman-
nan, are the main active compounds (H, 2008; MA,
1993). Acemannan has a backbone of β-1,4-D-mannosyl and β-1,4-D-
glucosyl residues, acetylated at the C2 and C3 positions on the mannose
residues, and some side chains of D-galactose attached to its C6.
Anthraquinones are secondary phenolic metabolites including
C-glucosyl derivatives such as barbaloin (10-glucopyranosyl-1,8-di-
hydroxy-3-hydroxymethyl-9-10H-anthracenone), a mixture of the two
diastereoisomers aloin A and B, as well as glucose-free compounds such
as aloeresin, aloenin and aloe-emodin (F et al. 2010). They were
found in the yellowish bitter exudate seeping out from freshly cut leaves
Agrochimica, Vol. LV - N. 5 September-October 2011
* Corresponding author:
Received XX Xx 2011 – Received in revised form XX Xx 2011 – Accepted XX Xx 2011
and were reported to have cathartic effects, anti-inflammatory effects in
vivo, to increase the peristaltic movements of the intestinal musculature
and also prevent the colon from reabsorbing water (G and
C-V, 2006; MA, 1993).
The acemannans are stored in the inner mucilaginous parenchyma of
the leaves, while anthraquinones are mainly localized in the outer rind
of leaves.
Processing of Aloe leaves, and in particular leaf pulp of A. bar-
badensis, has become a big industry worldwide due to the application in
the food industry (R and S R, 2008). Besides
a rapid degradation of the active compounds in different conditions
was described, the real content of aloin and acemannan in commercial
products is not usually declared (G and C-V,
2006; R and S R, 2008).
Industrial processes often involve heating, dehydration and grind-
ing, which may cause irreversible modifications to the active substances,
promoting important changes in the physiological and pharmaceutical
properties (T et al. 1992). Because of these improper process-
ing procedures, many Aloe products contain very little active ingredients
R and S R (2008). Improper storage conditions
can lead to degradation processes as well, as a consequence of tempera-
ture, light and humidity (G and C-V (2006).
In fact, leaves loose their biological activity at room temperature starting
from 6 hours from harvest (R and S R, 2008).
At present, few and discrepancy information is available on aloin
and polysaccharides content in Aloe-based commercial products and on
the stability of bioactives during storage. On this basis, our aim was to
investigate the stability of anthraquinones and acemannans during stor-
age at different conditions. With this purpose, whole leaf homogenate,
leaf gel homogenate, a very common household preparation from folk
medicine (father Zago’s recipe) and two commercial products (one
based on the whole leaf and another based on the sole leaf gel), were
considered. The stability of β-polysaccharides and aloin were investi-
gated in all the matrices considered as a function of temperature, oxygen
and addition of antimicrobial and antioxidant agents.
M  . – Leaves of A. barbadensis and A. arborescens were
taken randomly from three years old plants supplied by Dester Garden, Brescia, Italy.
Plant materials were immediately stored in freezer at -30°C until the beginning of the
experimental phase.
Preparation of test items. – Gel and whole leaf homogenates. – Leaf gel was gained
from A. barbadensis plants according to industrial applications for gel-based products.
Three fresh leaves from a basal, central and apical position were taken from 3 different
plants, and after manual removal of the peel, the gel fractions were pooled and homog-
enized by a blender.
As far as concerns A. arborescens, however, three fresh leaves from the central
and three fresh leaves from the lateral stem were taken from 3 plants. The leaves were
pooled and homogenized by a blender to prepare a representative sample of whole leaf
Samples with antimicrobial or antioxidant agents. To inhibit microbial growth,
a preservative of either 0.1% sodium azide or 0.1% of benzoate were added to different
samples of A. arborescens whole leaf homogenate and A. barbadensis gel.
In order to test the effect of antioxidants, samples of A. arborescens whole leaf
homogenate were prepared by adding 0.05% and 0.005% of ascorbate.
In both cases, an aqueous solution of each agent was prepared and then a volume
added to an accurate weight of matrix.
Commercial and household prepared products. – The most common worldwide
household preparation (father Zago’s recipe) was prepared by mixing in a blender 350 g
of A. arborescens whole leaf homogenate, 40 mL of grape brandy and 500 g of honey.
Furthermore, an A. barbadensis stabilized gel and a whole leaf homogenate (again
prepared according to father Zago’s recipe) commercial products were bought in a local
Test conditions.All samples were stored for 65±5 days in sealed glass tubes and
in dark. The quantitative analysis of aloin and β-polysaccharides was carried out at 5 dif-
ferent time points as minimum and the concentration values were compared with those
at the beginning of the test.
The tests with A. barbadensis gel and A. arborescens whole leaf homogenate with
the addition of an antioxidant agent were done at two different temperature conditions:
in refrigerator (+4°C) and at room temperature (+22°C). Those with the addition of anti-
microbial agents were instead carried out at room temperature (+22°C) only, in order to
enhance the effect of benzoate or sodium azide in a shorter time. As far as the oxygen
conditions are concerned, a further test with A. arborescens whole leaf homogenate to
which the antimicrobial agents were added, was done after an initial removal of air by
degassing with nitrogen.
Regarding the commercial products, the stability tests were carried out according to
the recommended or actual storage conditions. Tests with the preparation done accord-
ing to father Zago’s recipe was carried out stored at refrigerator temperature (+4°C)
while those with the stabilized gel was done at both refrigerator (+4°C) and room tem-
perature (+22°C). These different temperature conditions were chosen in according to
information in commercial labels.
Determination of anthraquinones and acemannan content. – Prior to be analysed,
each sample was visually examined in order to evaluate changes in appearance: color,
consistency, moulds development were checked at each sampling point. Anthraquinones
were then determined in each sample by liquid chromatography followed by tandem
mass spectrometry with electrospray ionisation source (LC-ESI/MS/MS) in the negative
mode, and quantified by the external standard method. A 1200 series liquid chromato-
graph system was used, equipped with quaternary pump, electrospray ionization system
and coupled to a G6410A triple quadrupole mass spectrometer detector (all from Agilent
technologies, Santa Clara, CA, USA). The plant material (2 g) was extracted by Ultra-
Turrax in 8 + 4 ml of ethyl acetate / methanol mixture (9:1 by volume) after adding 4 ml
of a 20% NaCl aqueous solution. After centrifugation (2000 g for 15 min) the extract
was diluted with methanol, filtered through a 0.45 m membrane and then analysed
by reversed phase LC-MS/MS using a Zorbax Eclipse plus C18 column (300 mm, 3.5
m) from Agilent. The solvent system used was water (solvent A) and acetonitrile (sol-
vent B) at a flow rate of 0.3 ml min-1; the gradient was designed to decrease solvent A
from 35% at 0 min to 20% at 2.5 min. The injection volume was 10 l and the drying gas
was nitrogen at 5 l min-1. Data handling was performed by ChemStation software under
Multiple Reaction Monitoring (MRM) acquisition: aloin transition was from m z-1 417
(M-H)- to 297 (collision energy 15 V).
Polysaccharides were instead determined colorimetrically at 540 nm, after binding
with the Congo red dye, on the basis of the work described by Eberendu et al. (2005).
Colorimetric measurements were done using a Perkin Elmer UV/VIS spectrometer
lambda 12. Aloe pulp (4 g) was extracted in 10 ml of double distilled water, on a hori-
zontal shaker for 2 h; 500 l of 1.3% KOH was added to the solution and then 2 ml
of Congo red solution (obtained diluting a saturated aqueous solution by a factor 50)
was also added. The solution was left for 1 h in dark and then analysed at λ = 540 nm.
Semi-quantitative determination of the solutions was carried out using a pure β-glucan
standard. Three measurements on three different extracts were performed for each leaf
pulp sample.
Raw data elaboration. – Single first order kinetic models were applied to describe
the degradation curves of bioactive substances in different Aloe products. Logarithmic
transformation of the measured concentrations was done and then the different log
concentrations were included in graphics in connection of the time, and modeled using
linear functions. Sufficient and adequate time points were chosen to ensure a robust esti-
mation of parameters; five points were used in all cases as minimum. Regression linear
coefficients (R2) were calculated to each linear regression curves.
The time for decrease in the concentration of β-polysaccharides and aloin from
100% to 50% (DT50) and to 10% (DT90) of the initial amount corresponding for each
analyte were numerically obtained through mathematical elaboration of different linear
regression curves slopes (k). The DT50 and DT90 were calculated as ln2/k and ln10/k
R  . The regression linear coefficients
showed a good correlation, ranging between 0.766-0.999 for the stability
of aloin and between 0.798-0.999 for β-polysaccharides. A worst corre-
lation (R2 = 0.502) was observed regarding the stability of the gel-based
commercial preparation only.
As far as visual assessments are concerned, the colour of Aloe gel
after preparation changed slightly from whitish to brownish after only
2 days of storage, and red mildews growth was observed after 7 days of
storage at room temperature. A similar behaviour was observed in Aloe
gel stored at +4°C, although the brown colouring occurred after 7 days of
storage and red mildews growth was observed after 14 days. Stabilised
gel commercial preparation stored at room temperature showed colour
alteration after 22 days of storage and any mildew grown for the whole
test period. Analogously, mildew growth was not observed in samples
with antimicrobial agents.
Regarding the whole leaf homogenate, a colour change from natural
dark green to light green was observed in all preparations, including
those with antioxidant agents. White mildews growth was observed in
all the preparations without antimicrobial agents, starting from 12 and
21 days of storage for room and refrigerate conditions respectively. The
colour of whole leaf based commercial product and that of the household
preparation (Father Zago’s recipe) stored at refrigerator temperature
remained stable and any microbial growth was observed.
The whole data concerning the stability of preparations, expressed
as DT50 and DT90, together with the corresponding correlation coef-
ficients, are presented in tables 1 and 2 for aloin and β-polysaccharides
respectively. The aloin content in the household preparation stored at
+4°C resulted more stable (DT50 = 108 days) than in all the whole leaf
homogenates tested, including those with antimicrobial or antioxidant
agents. Additionally, the samples at +4°C were more stable than those
at room temperature.
The aloin content in whole leaf based commercial product was
stable for the whole 70 days of testing, and therefore DT50 and DT90
T 1. – Stability of aloin in whole leaf homogenate and in the Father Zago’s household preparation.
Test item Storage conditions Additives Correlation
T (°C) Atmosphere
Whole leaf homogenate +22 air* - 0.924 20 66
Whole leaf homogenate +22 Air 0.1% Na benzoate 0.766 11 37
Whole leaf homogenate +22 Air 0.1% Na azide 0.760 11 38
Whole leaf homogenate +4 Air 0.005% ascorbate 0.960 14 45
Whole leaf homogenate +22 air 0.005% ascorbate 0.944 14 47
Whole leaf homogenate +4 air 0.05% ascorbate 0.999 26 86
Whole leaf homogenate +22 air 0.05% ascorbate 0.930 12 41
father Zago’s preparation +4 air - 0.889 108 360
* degassed with N2 immediately after homogenization
were not calculated. Regarding aloin stability in whole leaf homogenate
stored under vacuum conditions, the concentration was stable for 20
and 40 days at +22 and +4°C respectively. Hence, DT values were not
calculated because a linear disappearance trend could not be accurately
The stability of aloin in homogenates with antimicrobial agents
(DT50 = 11 days) was not significantly different from those without these
additives. Furthermore, there was no difference in stability between the
use of sodium azide and sodium benzoate.
In all cases, aloe emodin was detected in traces and sporadically,
proving that it is not the direct oxidative or microbial degradation prod-
uct of aloin.
As far as the stability of β-polysaccharides is regarded, the whole
gel samples stored at +4°C was more stable (DT50 = 11 days) than those
conserved at room temperature (DT50 = 2-3 days). The addition of either
sodium azide or sodium benzoate did not affect significantly the stability
of β-polysaccharides in the preparations, without significant differences.
However, the stabilised gel commercial preparation DT50 ranged from
12 days at room temperature to 44 days at +4°C, proving a higher stabil-
ity. Hence, the stability of β-polysaccharides is strongly affected by the
temperature of storage, while antimicrobial agents did not show signifi-
cant reduction of degradation. Similar results were achieved by Yaron
(1993), who evidenced changes in rheological properties at 40°C even
with antimicrobial agents, and by Chang et al. (1993) who observed a
relationship between degradation and temperature.
Generally, aloin stability in whole leaf homogenate was poor, and
neither ascorbate nor the antimicrobial agents could increase disappear-
T 2. – Stability of β-polysaccharides in aloe leaf gel and stabilised gel commercial.
Test item Storage conditions Additives Correlation
T (°C) Atmosphere
Leaf gel +4 air - 0.818 11 36
Leaf gel +22 air - 0.999 3 9
Leaf gel +22 air 0.1% Na benzoate 0.798 3 10
Leaf gel +22 air 0.1% Na azide 0.831 2 7
Commercial preparation +4 air - 0.502 44 148
Commercial preparation +22 air - 0.847 12 41
ance time. Temperature seemed to be quite more effective in reducing
aloin degradation, although storage at +4°C alone could not provide
acceptable stability as well. The results are in contrast with the findings
from Gutterman and Chauser-Volfson (2006) who observed a stability
of aloin in leaf exudate aqueous suspension at +4°C. The difference
may account in the different matrix from our study. On the other hand,
Chang et al. (2006) reported that Aloe polysaccharides stability was
higher at 70°C, do decrease at both lower and higher temperature; they
also described that aloin degrades quickly in these conditions. A further
evidence on aloin degradation when temperature increases has been
given by direct observations from Gulia et al. (2010) and by indirect
evaluations from Miranda et al. (2009).
F. 1. Representative regression lines through which degradation times of aloin (upper) and
β-polysaccharides (lower) were calculated.
Generally, the poor stability observed for both aloin and
β-polysaccharides in most of the conditions tested, helps to explain the
findings of Ramachandra and Srinivasa Rao (2008) who found a very
little amount of active ingredients in several aloe products.
Concluding, the preparation done according to Father Zago’s
recipe and the commercial one (prepared in a very similar recipe)
were stable at +4°C; all the other preparations showed a poor stability.
The improved stability might arise from the components of the recipe
different from Aloe components; the commercial product contained
citrate, ascorbate and sorbate which could affect the stability of the
preparation. Generally, the degradation of aloin does not seem to be
related to antioxidant or antimicrobial agents, albeit its degradation
mechanism is no clear yet.
The stability of β-polysaccharides is strongly affected by the tem-
perature of storage, while additives such as antimicrobial agents did not
lead to significant reduction of degradation. The stabilized gel commer-
cial preparation, is instead stable; although benzoate is reported among
ingredients, this might be due to the patented stabilization process.
Therefore, albeit temperature has been proved to play a major role
in aloin and β-polysaccharides stability, further attempts still need to be
done to clarify the key factors affecting the stability of Aloe fractions.
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S. – Aloe-based household preparations and commercial products are used
worldwide as a source of nutraceutical compounds, among which anthraquinones and
acemannan are the most known. However, it is reported that improper storage conditions
could lead to significant degradation processes, resulting in a low content of active sub-
stances. The aim of this work was to study the stability of aloin and β-polysaccharides
in aloe-based products during storage, as a function of temperature and chemical agents
Generally, aloin degradation in whole leaf homogenate was fast, and neither
ascorbate nor the antimicrobial agents could increase stability; a lower temperature
slightly improved stability, (DT50 up to 26 days at +4°C). Regarding the stability of
β-polysaccharides, a strong influence of the storage temperature was observed, while
antimicrobial agents did not show significant reduction of degradation. For both com-
pounds, household and commercial products were significantly more stable.
... It has found to be effective against various diseases like wound healing, asthma, HIV infections, teeth and gum protection and genital herbs. Also shows good results against anticancer, antioxidant, antidiabetic and anti inflammatory activities [15]. Bashir et al [16] denoted that aloe vera extract showed 100% active against all gram negative isolates and 75.3% active against gram positive pathogens. ...
Background Wet wipes have been commercially used for various purposes, to clean hard surfaces such as floors or kitchen surfaces including personal cleansing. Wet wipes were impregnated with a synthetic lotion for cleaning the skin, these wipes are hygienic because they are disposable and are normally discarded after their first use. Commercially available antiseptic Wet wipes have strong antimicrobial agents Triclosan and other chemicals. The present objective is to alternate the strong antimicrobial agents by using Herbal formulation in Wet wipes. With Aloe barbadensis miller gel and essential oils based antimicrobial formulation was used to prepare antiseptic wet wipes. Methods Antimicrobial (Agar well diffusion method), antioxidant (DPPH assay), toxicity studies (using Zebra fish embryo) were carried out in this study. Results The 0.5-2µg/ml of essential oil showed promising antimicrobial activity against standard routine bacterial pathogens, and also for Mycobacterium smegmatis wild strains. 100µg/ml of Tea tree oil and cinnamon oil were toxic to zebrafish embryo. However, sub-lethal doses of oils is (100 μg/mL) against Zebrafish embryo. Conclusion Thus, an eco-friendly, safe, low-cost herbal hand wipes are formulated for human use for prevention and protection against microbial infection and for maintaining personal hygiene.
... The techniques used include capillary electrophoresis [15] and High-Performance Liquid Chromatography (HPLC) with ultraviolet-visible detection [16]- [21]. The solvents used include water, isopropyl alcohol [20], phosphate buffered saline [22], ethyl acetate [23], ethanol [16] and methanol [24], though the methanol is more frequently used. The utilization of an ultrasensitive ionic liquid microextraction procedure has also been exploited [25]. ...
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Aloe barbadensis Miller (A. barbadensis) has been reported for use in the traditional management of malaria in Kenya. Aloin (an anthraquinone-C-gly-coside) is one of the therapeutic molecules in Aloe species that is responsible for their antimalarial effect. However, there is no report on the aloin content of A. barbadensis leaves latex and gel from Kenya. This study, therefore, isolated and quantified aloin levels in Phosphate Buffered Saline (PBS) extracts of A. barbadensis leaf gels and latexes sampled from Kisumu, Elgeyo-Marakwet and Baringo Counties of Kenya. Aloin was isolated by preparative thin layer chromatography and then subjected to thin layer chromatography and quantified using High-Performance Liquid Chromatography (HPLC). Results showed that the highest aloin content of 237.971 ± 5.281 mg aloin/g DW was for dry latex from Elgeyo-Marakwet followed by those from Baringo (198.409 ± 2.000 mg aloin/g DW) and then Kisumu (40.760 ± 0.088 mg aloin/g DW). Latexes had comparatively low aloin contents, and followed the order Kisu-mu > Baringo > Elgeyo-Marakwet. The HPLC method validation was satisfactory and exhibited adequate linearity, repeatability and accuracy. The HPLC method developed for identification and quantification of aloin in A. barbadensis leaves had high sensitivity, is specific, and the mobile phase systems and sample preparation method are simple. This can be used for quality control of Kenyan Aloe extracts. The results indicated intraspecific variation in aloin content of A. barbadensis leaf gels and latexes from different regions of Kenya.
... Despite the exceptional healing properties of the aloe vera plant, there are several limitations with keeping these active ingredients stable. The bioactivity of the plant decreases approximately 6 hours after harvesting [1,5]. Exposure to light, humidity and temperature can also diminish these significant properties. ...
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Nanofibers have been used with increasing success for drug delivery and various biomedical engineering applications. The mixture of 13% pullulan-aloe vera can be pumped with a minor effects on the flow behavior. The fiber is then characterized by SEM, shear viscosity, storage and loss moduli. The oscillatory shear data is employed. The mixture has a complex rheological properties that includes extreme shear-thinning as well as viscoelastic properties and yield stress. The rheology of the pullulan-aloe vera nanofber was characterized, the measurement method may influence the results, it is unclear how the behavior near walls influence the measurement method, Parallel-plate rheometer is used to measure rheological properties. The data and rheological parameters should facilitate a better understanding of the process-ability characteristics of the mixture. The cross model provides a simple way of quantifying the viscosity/shear rate profile for a shear thinning mixture. SEM images are carried out.
... Establishment of preservation conditions and manufacturing process of aloebased products must consider this degradation of aloin (Ramachandra and Rao 2006). Pellizzoni et al. (2011) have evaluated the stability of the main Aloe fractions and aloebased commercial products under different storage conditions. It was mentioned that aloin stability was not increased by ascorbate nor by the antimicrobial agents used. ...
... 10-Hydroxyaloins A and B were formed under any condition except at pH 2.0 and 3.0, and they were mainly formed under high temperature and at any light conditions. Pellizzoni et al. (2011) investigated the stability during storage at different conditions of anthraquinones and acetylated mannans (acemannans) in prepared and commercial gel and whole leaf homogenates from A. barbadensis and A. arborescens and in common household preparations from traditional medicine (Father Zago's recipe). The aloin content in the household preparation stored at +4°C resulted more stable (degradation time, DT 50 = 108 days) than in all the whole leaf homogenates tested, including those with antimicrobial or antioxidant agents. ...
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The Panel on Food Additives and Nutrient Sources added to Food (ANS) was asked to deliver a scientific opinion on the safety of hydroxyanthracene derivatives and to provide advice on a daily intake that does not give rise to concerns about harmful effects to health. Hydroxyanthracene derivatives are a class of chemical substances naturally occurring in different botanical species and used in food to improve bowel function. The ANS Panel reviewed the available scientific data on a possible relationship between hydroxyanthracene derivatives exposure and genotoxic and carcinogenic effects. On the basis of the data currently available, the Panel noted that emodin, aloe-emodin and the structurally related substance danthron have shown evidence of in vitro genotoxicity. Aloe extracts have also been shown to be genotoxic in vitro possibly due to the presence of hydroxyanthracene derivatives in the extract. Furthermore, aloe-emodin was shown to be genotoxic in vivo and the whole-leaf aloe extract and the structural analogue danthron were shown to be carcinogenic. Epidemiological data suggested an increased risk for colorectal cancer associated with the general use of laxatives, several of which contain hydroxyanthracene derivatives. Considering the possible presence of aloe-emodin and emodin in extracts, the Panel concluded that hydroxyanthracene derivatives should be considered as genotoxic and carcinogenic unless there are specific data to the contrary, such as for rhein, and that there is a safety concern for extracts containing hydroxyanthracene derivatives although uncertainty persists. The Panel was unable to provide advice on a daily intake of hydroxyanthracene derivatives that does not give rise to concerns about harmful effects to health. © 2018 European Food Safety Authority. EFSA Journal published by John Wiley and Sons Ltd on behalf of European Food Safety Authority.
... Establishment of preservation conditions and manufacturing process of aloebased products must consider this degradation of aloin (Ramachandra and Rao 2006). Pellizzoni et al. (2011) have evaluated the stability of the main Aloe fractions and aloebased commercial products under different storage conditions. It was mentioned that aloin stability was not increased by ascorbate nor by the antimicrobial agents used. ...
... In numerous pre-clinical and clinical studies the Aloe gel has exhibited various pharmacological activities and therapeutic effects such as anti-inflammatory, antimicrobial, antiplasmodial, antimalarial, antioxidant and anticancer activity (Grace et al., 2008;Lucini et al., 2015a). It has been postulated that these biological properties of Aloe extracts can be ascribed to the synergistic action of several phytochemicals and antioxidants (e.g., phenolics, polysaccharides and vitamins) (Romani et al., 2008;Pellizzoni et al., 2012a;Lucini et al., 2015a). Among phenolic compounds, aloin was widely studied as one of the main biologically active components of Aloe exudates (Liao et al., 2006;Javed and Atta-Ur, 2014). ...
Over the past years, interest in the phytochemical profile of Aloe species (family: Xanthorrhoeaceae) has been on the rise, compelled by its popularity as an ingredient in cosmetic formulations, food supplements and drug design. It is surprising that only few Aloe spp. have been grown and commercialized; this might be due to the very limited knowledge of their potent bioactive compounds. The phytochemical profile of eighteen Aloe species was investigated using colorimetric assays, triple quadrupole and time-of-flight mass spectrometry, focusing on bioactive secondary metabolites in leaf exudates. The phytochemical profile of leaf exudates from different species was widely diverse and included free and glycosylated chromones (mainly aloeresins, with a content of aloeresin A up to 843.4 g 100 g⁻¹) followed by the anthraquinones aloin (0.66–4.96 g 100 g⁻¹) and hydroxyaloins. Among the examined species A. marlothii, and A. melanacantha were found to be richest in total polyphenols (14.3 and 6.4 g gallic acid equivalents 100 g⁻¹), flavonoids (up to 7.1 g rutin equivalents 100 g⁻¹), flavonols (up to 5.0 g rutin equivalents 100 g⁻¹), and presented the highest antioxidant activity (up to 810.3 μmol g⁻¹ trolox for DPPH, and 453.4 μmol g⁻¹ trolox for ORAC), aloin, and aloeresin A contents. A second cluster, including A. arborescens and A. nyeriensis, was characterized by high contents of total phenolics and aloenin. These findings highlight for the first time the complex profile of phytochemicals in aloe leaf exudates and open new horizons to the industrial use of these Aloe species, which could represent a smart approach to increase the growers’ income.
Barbaloin (10 – glucopyranosyl – 1,8 – dihydroxy – 3 – (hydroxymethyl) – 9(10H) – anthraquinone: aloin A), present in Aloe species, is widely used in food, cosmetic and pharmaceutical industries. Here we characterize its optical absorption and emission spectra in aqueous solution at different pH values. Through pH titration, using both absorption and fluorescence spectroscopy, two pKa values for Barbaloin were determined: pKa1=9.6±0.6 and pKa2=12.6±0.8. These acidity constants were found to be higher than those found for Emodin, a similar molecule which lacks the sugar moiety present in Barbaloin. Performing quantum mechanical calculations for non-ionized, singly, doubly, and triply deprotonated forms of Barbaloin in vacuum and in water, we assigned the positions of the site for the first and third deprotonation in the anthraquinone group, and the second deprotonation in the glucose group. The instability of Barbaloin in high pH solutions is discussed here, and the optical absorption and fluorescence spectra due to products resulted from Barbaloin degradation at high pH is well separated from the Barbaloin original spectra. Biological fluids have specific pH values to maintain homeostasis, hence determining the pKaof Barbaloin is important to evaluate the mechanism of action of this drug in different parts of an organism as well as to predict pharmacological relevant parameters, such as absorption, distribution, metabolism, and excretion.
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The present study explored the stability of extracted anthraquinones (aloin, aloe-emodin and rhein) from whole-leaf Aloe vera gel (WLAG), its freeze-dried powder (FDP) and spray-dried powder (SDP) under varying pH and temperature conditions during storage. Each anthraquinone behaved differently under different processing parameters. The amount of anthraquinones present in the gel was higher than in FDP and SDP. The aloin contents decreased by more than 50% at 50 °C and 70 °C, while at 25 °C and 4 °C, the decrease was moderate. A substantial reduction in aloin concentration was noticed at pH 6.7, whereas it remained unaffected at pH 3.5. The temperature and pH had no significant effect on the stability of aloe-emodin. Interestingly, a small quantity of rhein was detected during storage due to the oxidative degradation of aloin into aloe-emodin and rhein. These findings can provide significant insight into retaining anthraquinones during processing while developing functional foods and nutraceuticals to obtain maximum health benefits.
Aloin is an anthraquinone-C-glycoside present in Aloe vera This compound is extremely variable among different species and highly depends on the growing conditions of the plants. The quantification of aloin in different extraction preparations has been a frequent problem due to the high instability of the compound. The aim of the present study is to develop and validated an analytical method for aloin detection in fresh and dry samples of Aloe barbadensis gel and latex using high performance liquid chromatography coupled to a diode array detector (HPLC-DAD). Phosphate buffered saline (pH 3) was selected as the extraction solvent. The aloin was separated using a Zorbax Eclipse AAA column (4.6 × 150 mm) at 35°C, and water and acetonitrile were used as the mobile phase at a flow rate of 0.9 mL/min. The linearity was satisfactory with a correlation coefficient greater than 0.999. Under these conditions, the method precision (relative standard deviation) was 3.71% for FL, 4.41% for dry latex, 0.81% for fresh gel and 4.42% for dry gel samples. Aloe latex was determined to have a greater amount of aloin than aloe gel. The method validation was satisfactory and exhibited adequate linearity, repeatability and accuracy.
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Proper scientific investigations on Aloe vera have gained more attention over the last decade due to its reputable, medicinal, pharmaceutical and food properties. Some publications have appeared in reputable scientific journals that have made appreciable contributions to the discovery of the functions and utilizations of Aloe vera lacking processing of leaf gel. Present processing techniques aims at producing best quality aloe products but end aloe products contain very little or virtually no active ingredients. Hence, appropriate processing techniques should be employed during processing in order to extend the use of aloe vera gel. Further research needs to be done to unravel the myth surrounding the biological activity and the exploitation of aloe constituents.
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Many of the health benefits associated with Aloe vera have been attributed to the polysaccharides contained in the gel of the leaves. These biological activities include promotion of wound healing, antifungal activity, hypoglycemic or antidiabetic effects antiinflammatory, anticancer, immunomodulatory and gastroprotective properties. While the known biological activities of A. vera will be briefly discussed, it is the aim of this review to further highlight recently discovered effects and applications of the leaf gel. These effects include the potential of whole leaf or inner fillet gel liquid preparations of A. vera to enhance the intestinal absorption and bioavailability of co-administered compounds as well as enhancement of skin permeation. In addition, important pharmaceutical applications such as the use of the dried A. vera gel powder as an excipient in sustained release pharmaceutical dosage forms will be outlined.
Aloe vera leaves were dried at different temperatures in hot air oven and powdered. The percent powder yield was found 2.60%, 2.60%, 2.55% and 2.52% at 50, 60,70 and 80 degrees C respectively. Powder samples had the pH (1% solution) 3.51, 3.53, 3.52 and 3.53 with the rise of drying temperature in the selected range. Statistically, yield and pH indicated no significant difference (p < 0.5) due to drying temperature variation. Wettability of powder at 70 degrees C was 32 s as compared to 35, 35 and 37s in the samples obtained at 50, 60 and 80 degrees C respectively. Water absorption capacity of powder at 70 degrees C was 359% as compare to 351%, 354% and 356% of 50, 60, and 80 degrees C powder samples. The HPLC chromatogram obtained for the sample dried at 80 degrees C shows that as the temperature increased from 50 to 80 degrees C, aloin content decreased from 10.6 to 1.7 ppm. The "a" values were found 2.028, 2.226, -0.282 and 2.531 for the samples obtained after drying at 50, 60, 70 and 80 degrees C respectively. Samples obtained at 70 degrees C showed negative "a" value indicated that the sample was more greenish in colour as compared to other samples.
The polysaccharides present in Aloe vera gel are presumed to play a key role in the clinical activity of the gel. While clinical studies generally confirm the contribution of the gel to a reduction in inflammation and an acceleration of healing, in some cases the expected therapeutic activity is not observed. This variability could perhaps be attributed to differences in the source of the gel, horticultural conditions and/or post-harvest treatments. Accordingly, polysaccharide content and composition and gel consistency were studied as a function of growth conditions in gels obtained from shrubs of Aloe barbadensis Miller grown in the Negev region of Israel. Autodegradation of the polysaccharides in the freshly produced gel was also characterized, and a method was developed for retarding this process. The polysaccharides were found to consist of glucomannans. Polysaccharides constituted 0.2–0.3% of the fresh gel and 0.8–1.2% of the dry matter content. Irrigation had a greater influence on gel composition than leaf age or season. The fresh gel showed pseudoplastic behaviour, which became Newtonian as a result of post-production autodegradation. The polysaccharides remaining after degradation were mainly mannans. Addition of a natural polysaccharide extracted from a species of red microalgae produced a soft pseudoplastic gel with synergistic rheological properties. The addition of the algal polysaccharide preserved the physical properties of the natural aloe polysaccharides. Chemical means were used to retard microbial degradation.
Aloe arborescens is a very important plant used in the cosmetics and pharmaceutical industries. The main problem using this plant for medicinal and cosmetic purposes is the rapid destruction of the active compounds in aquatic solutions. By frequently pruning the leaves, the content of three secondary phenolic metabolites (SPhMs), barbaloin, aloeresin and aloenin, in the leaves can be increased dramatically. The changes in these SPhMs were studied in an aqueous suspension of leaf exudate powder and in harvested leaves after storage for 1–45 days at 4 °C in darkness. During storage in water there was rapid degradation of aloenin, but a gradual and slow degradation of barbaloin and aloeresin. In contrast, in stored leaves, the change in the relative amounts of the three SPhMs was similar, but the percentage of aloenin was higher even after 3.5 months. When these SPhMs are stored as dry powder they may last for some years.
The effect of air temperature on the physicochemical and nutritional properties and antioxidant capacity of Aloe vera (Aloe barbadensis Miller) gel was investigated. The following parameters were analysed: proximal composition, water activity (aw), pH, acidity, non-enzymatic browning, surface colour, vitamin content (C and E), mineral content, and antioxidant capacity. The drying kinetics of A. vera gel was modelled using the Wang–Singh equation, which provided a good fit for the experimental data. Analysis of variance revealed that the drying temperature exerted a clear influence on most of the quality parameters. A drying temperature of 80 and 90 °C resulted in significant variation in and/or loss of the physicochemical and nutritional properties of the gel; in addition, the antioxidant capacity of the gel was decreased at these temperatures. These effects were also observed as a result of a lengthy drying period (i.e., 810 min at 50 °C). However, minor alterations in the physicochemical and nutritional properties of A. vera gel were produced at drying temperatures of 60–70 °C, resulting in the production of a high quality gel.
Research was conducted on the gel juice from Aloe vera, a traditional medicinal plant, to investigate the effects of heat treatment on bioactive substances including polysaccharide and barbaloin. The effect of methanol solvent on compositional variations of barbaloin was also taken into consideration. Results show that the polysaccharide from Aloe vera exhibited a maximal stability at 70 °C decreasing either at higher or lower temperatures. Heating promoted a remarkable decrease in barbaloin content depending on temperature and time, more affected than polysaccharide of the gel juice from Aloe vera. Barbaloin is unstable when dissolved in methanol resulting in the transformation into a series of unidentified compounds, in addition to aloe emodin with the period of storage at 4 °C in refrigerator.
This article proposes a chromatographic method for the analysis of extracts of Aloe plants. The method was developed with a laboratory assembled nano-LC system coupled with a UV detector, followed by an IT-mass spectrometer. With a step gradient mode of ACN/H(2)O mixtures and employing a capillary column packed with C(18) (100 μm id), a complete separation of the following anthrones was achieved: aloin (in its two isomeric forms A and B), 5-hydroxyaloin and 7-hydroxyaloin (in its two isomeric forms A and B). The optimized nano-LC-MS method was validated for the quantification of aloin, the main component of Aloe with known pharmacological activities. RSD values obtained for retention time and peak areas were 1.3 and 12.1%, respectively. LOD and LOQ values of 0.4 and 1.5 μg/mL were obtained for each aloin isomer. The method was applied to the analysis of Aloe vera and A. ferox extracts in order to acquire a fingerprint, characteristic for each plant. Several phenolic compounds were detected by UV and identified by MS. A. vera and A. ferox showed different profiles and it was possible to discriminate them. Several commercial formulations, declared to contain Aloe extracts, were analyzed. Comparing their chromatograms with those obtained from A. vera and A. ferox, it was possible to recognize the Aloe species and to determine aloin.
The quinoid anthracycline-related anti-cancer agents represent an important group of anti-tumour drugs with a wide spectrum of activity. We review here some of the separation techniques used for the analysis of anthracyclines and related compounds. In this review we have covered a range of compounds from the early anthracycline antibiotics such as doxorubicin to the more recent anthracenediones and anthrapyrazoles such as mitoxantrone and losoxantrone, respectively. We also include novel compounds such as AQ4N and C1311, both awaiting clinical trial. Separations of the anthraquinone related anti-cancer agents are predominantly by HPLC. These separation techniques have been used for a variety of applications including drug stability, protein binding and therapeutic drug monitoring as well as detailed pharmacokinetic and metabolic studies. Pharmacokinetics, and therefore drug analysis, plays a central role in both the development of new agents and also leads to a better understanding of clinically established agents in this class. Sample preparation and extraction methods including solid-phase and liquid-liquid extraction have also been highlighted. Many anthraquinone related compounds are highly coloured and fluoresce. They are suitable for a range of detection methods including UV-Vis, electrochemical and fluorescence. The methods described are used for sometimes complex separations that are needed for the evaluation of such compounds in biological samples.