Latin name Aloe barbadensis
Pharmacopoeial name Aloe barbadensis
Other names Aloe Vera.
About Aloe vera
Aloe barbadensis Miller, commonly referred to as Aloe vera, is one of approximately 420 species of Aloe belonging to the lily family that originated in South Africa, but are now indigenous to dry sub-tropical and tropical climates, including the southern United States.
Aloes are perennial succulents that are adaptable to habitats with low or erratic water availability, and are characterized by the capacity to store large volumes of water in their tissue. Aloes green fleshy leaves covered by a thick cuticle or rind and an inner clear pulp. The rind of the Aloe vera leaf accounts for approximately 20 % by weight of the whole plant leaf, and the pulp represents the remainder (1). Aloe vera latex is also commonly referred to as “aloe juice,” “aloe sap,” or simply “aloe.” The Arabic word “alloeh” means shining and bitter, and likely refers to the bitter-tasting Aloe latex. Aloe vera gel is the clear mucilaginous aqueous extract of the leaf pulp.
The Aloe vera plant has been used in folk medicine for over 2000 years, and Aloe vera has remained an important component in the traditional medicine of many contemporary cultures. The Aloe vera plant has a historical reputation as a topical healing agent for abrasions and burns, and as an emollient and moisturizer by the cosmetic industry. Different cultures use Aloe vera in much the same way. The latex, which drips from the plant when cut, is applied to the skin area, or the leaf is split lengthwise and either laid directly on the skin or the inner gel scrapped out and applied as an ointment. In Western societies, Aloe vera was historically mainly prized to supply the latex component of the leaf to the pharmaceutical industry (2).
Uses
The two commercial products obtained from the inner and outer fleshy leaf pulp of the Aloe vera plant are aloe vera gel and Aloe vera latex. From these products, three distinct types of preparation are used as topical or oral therapeutic agents:-Aloe vera latex is a laxative generally regulated as a drug, but is also used as a bitter flavouring additive by the food industry; Aloe vera gel is primarily a topical agent for skin wounds and irritations but is also taken internally for the treatment of gastric ulcers and diabetes; Aloe vera whole leaf extract, combines both the gel and latex, and is popular as a dietary supplement for various systemic ailments.
Both classes of leaf products, the gel and latex, are reported to possess a wide range of pharmacological activities, but these claims are not always supported by well-controlled studies. A major obstacle in evaluating results of experimental studies and clinical trials of the effects of Aloe vera is differentiating clearly the part of the plant used and which species was under investigation. For example, Aloe vera juice, which is used to describe the latex from the bundle sheath cells, is also the liquid obtained from maceration of the whole leaf. Furthermore, not all products are equivalent. Factors such as the species, growing and harvesting by conditions, plant components, and extraction and processing methods affect the concentration and potency of the various constituents of Aloe vera and their beneficial potential. (3,4).
Aloe vera is available in a large range of skin moisturizers, face and hand creams, cleansers, soaps, suntan lotions, shampoos and hair tonics, shaving preparations, bath aids, makeup and fragrance preparations, and baby lotions and wipes. Topical preparations of Aloe vera have been used to treat frostbite (5), burns (6) radiation dermatitis (7, 8), ulcers (9), psoriasis (10), wounds (11-15), and skin infections (16).
Cholesterol/ Triglyceride/Glucose Metabolism
Twelve weeks of daily administration, the 10- or 20-ml whole leaf Aloe vera extracts has been shown to decrease total serum cholesterol by 15.4% and 15.5%, triglycerides by 25.2% and 31.9%, and low-density lipoproteins by 18.9% and 18.2%, respectively (17).
Agarwal also examined the effect of oral consumption of Aloe vera gel on risk factors of heart disease. 5000 patients were selected for the study; all presented symptoms of heart disease (18). The patients consumed breads prepared with wheat flour and Aloe vera gel at two meals a day for a period of three months. There was a marked reduction in total lipids, serum cholesterol, and serum triglycerides. In addition, patients who also had diabetes showed reductions in fasting and post-meal blood glucose levels.
Skin Healing
Rodriguez-Bigas et al. found the average complete healing time was substantially shorter in an Aloe vera-treated group (19). A different commercial preparation of Aloe vera gel, either alone or in combination with anti-microbials, was examined for in vitro cell growth and wound healing of excision wounds, and was found to enhance cell proliferation and increase the tensile strength of wound scars (20).
The ability of Aloe vera to heal ulcers, rashes, or poorly healed scars associated with radiation therapy was evaluated in two phase III trials in women who had undergone radiation therapy to the breast or chest wall (21). The results were identical on both treatment arms, with Aloe vera gel offering no benefit. Similar effects were observed in a phase III study involving 225 patients who received either topical Aloe vera gel or aqueous cream applications. (22) Olsen compared Aloe vera gel with mild soap cleansing to mild soap cleansing alone during radiotherapy examining the time to first observed radiation-induced skin change in 73 patients(23). The investigators found that at higher cumulative doses, the Aloe vera gel and mild soap group were lesion-free for a longer time than the mild soap alone group.
Psoriasis
The efficacy of Aloe vera gel in the treatment of psoriasis was examined in a double-blind, placebo-controlled, randomized, comparison study. The sum score of erythema, infiltration, and desquamation was measured and was found statistically significant in favour of the placebo treatment (24). Opposing results were observed by topical self-application of Aloe vera gel or placebo cream to 60 patients with mild to moderate psoriasis (25). The creams were applied thrice daily for four weeks, and the cure rate in the Aloe vera-treated group was statistically significant, with no relapses reported in a 12-month follow up period.
Only a few studies have examined the influence of oral administration of Aloe vera gel on the wound-healing process. Davis evaluated the effects of food grade Aloe vera (26). Wounds healed more rapidly in Aloe vera treated group compared to untreated or vehicle controls, suggesting that that food grade Aloe vera was an effective treatment in the healing of wounds.
Immunomodulation
Most of the reports focused on the immunomodulating effects of Aloe vera gel, concentrate on acemmanan and other polysaccharides found in the gel. Although there is a general consensus among the studies that the polysaccharide fraction of Aloe vera gel has immunomodulating activities, the identity, size, and composition of the major immunomodulating polysaccharide are not known. Unfortunately, many studies were conducted using either complex commercial products or poorly characterized plant components.
Colitis
In a randomized, double-blind, placebo-controlled trial of the efficacy of Aloe vera gel for the treatment of mildly to moderately active ulcerative colitis, patients were administered Aloe vera gel in a drink twice daily for four weeks. (27). The Simple Clinical Colitis Activity Index and histological scores decreased significantly; however, the sigmoidoscopic scores and laboratory values showed no significant differences from placebo controls.
Anti-Bacterial/Anti-Viral effects
Interest in acemannan has grown since demonstration of its anti-viral properties in vivo. Womble and Helderman published the first study suggesting that acemannan had an anti-viral effect on human cells (28). Other studies have shown that certain mannosylated substances activate macrophage cells and enhance the killing of pathogens, such as Candida albicans (29). Stuart investigated whether acemannan would also enhance macrophage function (30). Exposure of macrophage cells to acemannan resulted in significantly enhanced killing of C. albicans compared with untreated controls. Aloe vera gel was shown to inhibit the growth of gram-positive bacteria, Shigella flexneri and Streptococcus pyrogenes (31).
Safety
Ingestion of crude Aloe vera gel at doses greater than 110 mg/kg/day produced diarrhoea, slower growth, polydipsia and polyuria in rats (32). Longer-term studies showed that ingestion of Aloe vera gel altered calcium metabolism (33).
Excess consumption of Aloe vera latex is also associated with watery diarrhoea leading to electrolyte imbalance and hypokalaemia.
Keywords Cholesterol/Triglyceride/Glucose Metabolism; Skin Healing; Psoriasis; Immunomodulation; Colitis; Anti-Bacterial/Anti-Viral effects
Monograph
Assessment report
References
References
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