Medical Attributes of Aloe vera - The Aloe Plant
by K-C-Ann Creque, Michelle Junker, and Mariana Yevtukh
Aloe vera, a member of the
Liliaceae (Lily Family), is commonly used in herbal medicine and is
believed to have originated in Northern Africa. The term ‘vera’,
meaning ‘true’, was coined by Linnaeus as the genus Aloe contains 250 species. However,
the particular species, Aloe vera,
is the best known of all the species (Neutraceutical, 1996). It can be
found growing in the tropical climates of the Southern United States,
India, South America, Central America, the Caribbean, Australia, and
Africa. Some taxonomists now refer to the species Aloe vera as Aloe barbadensis. This is somewhat
misleading as the plant is not believed to have originated in Barbados
(Ombrello 2009). Aloe vera is
often referred to as just ‘Aloe’ and has been used for thousands of
centuries dating back to the Ancient Egyptians.
Aloe vera can be characterized
by thick, tapered, spiny leaves that grow from a short stalk near
ground level. It is often mistaken for cactus but is phylogenetically
related to members of the Lily family (Ombrello 2009). From the base of
the plant, the leaves grow in a rosette pattern and can extend up to 4
feet. The number of leaves on each plant varies from around 12 to 16,
with each leaf weighing up to three pounds (Neutraceutical, 1996).
A. vera is used extensively as
an herbal remedy for treating human illnesses. Countries such as
Trinidad and Tobago, India, Mexico, Canada, and Nigeria employ the use
of Aloe for various
treatments, including “gastrointestinal ailments
(ulcerative colitis, ulcers, constipation, colitis, and laxative),
musculoskeletal ailments (osteoarthritis, bursitis, and cold sores),
diabetes, asthma, radiation-related mucositis, epilepsy, bleeding,
amenorrhea, depression, glaucoma, multiple sclerosis, hemorrhoids,
varicose veins, burns, wound healing, psoriasis, sunburn, and
frostbite” (Rodriguez-Fragoso et al., 2009).
A. vera enjoys widespread use
as a panacea, or cure-all. For instance, Aloe is commonly used as a “daily
supplement” in many
cultures, especially India. The plant is used for “cosmetic, medicinal,
and nutraceutical purposes” (Vaidya and Devasagayam, 2007) due to its
antioxidant properties (Vaidya and Devasagayam, 2007). Many do include
Aloe in the diet as an aspect
known as “functional food” (Vaidya and
Devasagayam, 2007), which is designed to improve health by regular
consumption. Those who consume Aloe may suggest that the plant helps to
relieve or prevent chronic illness (Vaidya and Devasagayam, 2007),
while promoting general health.
Useful chemical compounds in the Aloe
plant are typically isolated from two materials: a latex and a gel
(Modak et al., 2007). Out of the approximately 80 constituents
distinguished in Aloe vera,
only a few chemical species have enough scientific literature to
substantiate their medical significance through experimental studies
and clinical trials. However, scientific studies have determined the
effects of the following isolated compounds: barbaloin, acemmanan, and
B-sitosterol. The anthraquinone, barbaloin, is the active purgative
principle found the latex layer (Smith, 1851). Barbaloin prevents the
opening of chloride channels in the colonic mucosa, causing an increase
in peristaltic activity in the large intestine and softer stool
(Boudreau et al., 2006). Thus, Aloe
is often used as an irritant purgative to treat constipation. The
polysaccharide acemannan contains unique β-1→ 4 glycosidic bonds that
are thought to be responsible for its immunomodulating (Ramamoorthy et
al., 1996), anti-viral (Womble, 1988), and anti-tumor activities (Peng
et.al., 1991). B-sitosterol is a plant sterol found in the sap that has
anti-inflammatory properties (Langmead et.al., 2004) as well as
angiogenic effects (Lee et.al., 1998). Barbaloin and acemmanan are both
found only in A. vera, while
B-sitosterol is found across many plant species.
Use of A. vera as an
effective panacea is not supported by scientific literature.
However, scientific studies have validated the use of A. vera in controlled settings for
the treatment of specific illnesses such as diabetes, high cholesterol,
viruses, abdominal pain, and superficial wounds.
A. vera is commonly associated
with the healing of burns, but its clinical efficacy is
questionable. A systematic review examined four trials in which Aloe was used to treat burn wounds.
This review found that in general, the healing time of the Aloe group versus the control group
was approximately 8.79 days shorter. However, they concluded that due
to the varying contents of the Aloe
products used, definitive evidence of its effectiveness could not be
found (Maenthaisong et al., 2007). This result is in accordance with
the general consensus made in the majority of scientific studies; since
different Aloe products are used in different studies the wound healing
process varies from study to study (Boudreau et al., 2006).
Aloe vera is most commonly
used to treat diabetes due to its ability to reduce blood glucose
levels (Rodriguez-Fragoso et al., 2009). Lans (2006) found that
of 622 diabetics in Trinidad and Tobago, 152 used herbal remedies to
treat their disease. She found that A.
vera was the most commonly used plant among the 24% of people
who treated their diabetes with plants. A literature study found ten
studies in which the oral administration of A. vera lowered blood glucose
levels in diabetic patients and reduced blood lipid levels in patients
exhibiting hyperlipidaemia (Vogler et al., 1999). Another study
suggested that A. vera also
has additive effects when combined with anti-diabetes drugs
(Rodriguez-Fragoso et al., 2007). Since the administration of aloe
extracts attenuated oxidative damage in the brains of
sptreptozotocin-induced diabetic rates, the glucose-lowering may be
mediated by an anti-oxidant mechanism (Parihar et al., 2004).
Research indicates that Aloe
may be useful in lowering high cholesterol and other risk factors
associated with heart disease, though the mechanism is unknown.
When 60 patients received a daily administration of extract for 12
weeks, it was found that total serum cholesterol levels, triglycerides,
and low-density lipoproteins were reduced (Can et al., 2004). In
another study in which 5,000 patients that exhibited symptoms of heart
disease consumed bread prepared with A.
vera gel two times a day for three months, noted a marked
reduction in total lipids, serum cholesterol, and serum triglycerides
Several studies have shown that that mucopolysaccharide acemannan
isolated from A. vera has an
anti-viral effect helpful in treating viruses such as herpes simplex,
chickenpox, and flu (Womble, 1988). The administration of acemannan to
feline leukemia virus-infected cats by either intravenous injections,
subcutaneous injections, or oral administration increased their
survival rates, increased lymphocyte, and decreased neutrophil counts
(Yates et al, 1992). Womble and Helderman (1988) showed that acemannan
significantly enhanced the alloantigenic response in a mixed lymphocyte
assay derived from humans. In addition, Start et al. demonstrated the
effectiveness of acemannan in vitro
in an experiment in which the exposure of macrophage cells in vivo to acemmanan significantly
enhanced the killing of Candida
albicans (Gelderman et al., 1998).
Oral administration of A. vera
has occasionally been reported in cases of severe abdominal pain or
cramping. When used as a topical treatment, some persons may develop an
allergic reaction characterized by itching or the development of a skin
rash. As previously stated, the gel obtained from Aloe has been used as a strong
laxative. As this is the case, over-use may lead to electrolytic
imbalances, alongside intestinal cramps and/or diarrhea (Rodriguez et
al., 2007). In fact, products containing Aloe were once regulated by the FDA
as an over the counter laxative but regulations by the FDA have been
discontinued (NCCAM, 2006). The plant possesses pyrrolizidine alkaloids
which raises concerns regarding whether or not the plant can induce
abortion, menses, and fetotoxicity (Rodriguez-Fragoso et al., 2009).
Due to the toxic compounds and its lack of regulation, this herbal
treatment is not recommended for pregnant women, children, the elderly
or persons suffering with diabetes (Anonymous, 2005). Furthermore,
persons with diabetes can incur a hypoglycemic effect (Rodriguez et
al., 2007). Persons experiencing severe stomach pain, gastrointestinal
illnesses, and appendicitis are discouraged from using A. vera. Although the plant may
have therapeutic effects, the pyrrolizidine alkaloids and
anthraquinones can cause adverse reactions that may impede recovery or
severely injure the patient.
Aloe does have beneficial
effects for treating epidermal and superficial disorders and wounds. Aloe may also be useful to treat
certain illnesses, such as diabetes and inflammatory digestive
ailments, pending further clinical studies. However, despite the
possible benefits of the plant, there exist concerns regarding its
miscarriage risks, fetotoxic properties (Rodriguez-Fragoso et al.,
2009), and general misuse. While tradition may suggest that Aloe can be a miracle plant,
treating superficial issues from burns and psoriasis, to diseases like
epilepsy and glaucoma (Rodriguez-Fragoso et al., 2009), more research
must be performed in order to determine both the benefits and
repercussions of the use of Aloe
in Complementary Alternative Medicine (CAM) and conventional medicine.
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This paper was developed as part of the BIO 368 - Medical Botany
course offered at Wilkes University during the spring of 2009. Course
instructor was Kenneth M. Klemow, Ph.D.
The information contained herein is based on published sources, and
is made available for academic purposes only. No warrantees,
expressed or implied, are made about the medical usefulness or
dangers associated with the plant species in question.
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