Medical Attributes of Aloe vera - The Aloe Plant

by K-C-Ann Creque, Michelle Junker, and Mariana Yevtukh
Wilkes University
Wilkes-Barre, PA

May, 2009

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 (Agarwal, 1985).

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.

LITERATURE CITED

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Boudreau, M.D. & F.A. Beland, Frederick.  2006. An evaluation of the biological and toxilogical properties of Aloe barbadensis (Miller), Aloe vera. Journal of Environmental Science and Health. 24, 103-154.

Can, A., N. Akev, N. Ozsoy, S. Bolkvent, B.P. Arda, R. Yanardag, & A. Okyar. (2004). Effect of Aloe vera leaf gel and pulp extracts on the liver in type-II diabetic rat models. Biol Pharm Bull 27:694-698.

Clement, Y.N. , et al. 2005. Medicinal herb use among asthmatic patients attending a specialty care facility in Trinidad. BMC Complement Altern Med., 5, n.p.

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Lans, C.A.  2006. Ethnomedicines used in Trinidad and Tobago for urinary problems and diabetes mellitus. J. Ethnobiol Ethnomed., 2, n.p.

Lee, M.J., O.H. Lee, S.H. Yoon, S.K. Lee, M.H. Chung, Y.I. Park, C.K. Sung, J.S. Choi, & K.W. Kim.  1998. In vitro angiogenic activity of Aloe vera gel on calf pulmonary artery endothelial (CPAE) cells. Arch Pharm Res. 21:260-265.

Maenthaisong, R., N. Chaiyakunapruk, S. Niruntraporn, & C. Kongkaew. 2007. The efficacy of aloe vera used for burn wound healing: a systematic review. Pharmacy Practice Unit, 6: 713-8.

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Yates, K.M., L.J. Rosenberg, C.K. Harris, D.C. Bronstad, G.K. King, G.A. Biehle, B. Walker, C.R. Ford, J.E. Hall, I.R. Tizard.  1992. Plot study of the effect of acemannan in cats infected with feline immunodeficiency virus. Vet Immunol Immunopathol 35: 177-189.

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. (kenneth.klemow@wilkes.edu). 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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This page posted and maintained by Kenneth M. Klemow, Ph.D., Biology Department, Wilkes University, Wilkes-Barre, PA 18766. (570) 408-4758, kenneth.klemow@wilkes.edu.