Aloe Vera Products

Description

Aloe juice, pulp, extracts, concentrates and leaf segments come from the Aloe vera plant. Aloe vera is also known as Aloe barbadensis, Aloe perryi, Aloe ferox, Mediterranean Aloe, Barbados Aloe and Curacao Aloe.

Aloe is the solid residue obtained by evaporating the latex from beneath the skin.

Aloin is a mixture of water-soluble glycosides obtained from aloe.

Aloe gel is a clear, thin, gelatinous material obtained by crushing the inner tissues of the leaves.

Aloe vera is cultivated around the world, particularly in sandy loam type soils, such as found in North America in the Rio Grande Valley of Texas and Mexico. However, the plant grows naturally throughout the world in most tropical and subtropical areas, particularly Jamaica, Barbados, Aruba, Puerto Rico, Central America, the Mediterranean countries, Egypt, Malaysia, Indonesia and India.

The plant blooms in late winter and early spring. It is primarily sought for its pulp, which is 96% water. However, other parts of the plant, such as the seed and root oils are also used in a variety of food products. Food products containing some part of the aloe vera plant include nonalcoholic beverages, frozen dairy desserts, candy, baked goods, gelatins and puddings. The outer epidermis (aloin layer) is green and rubbery. It contains a yellow exudate chemically known as barbaloin (an anthraglycoside), a potent cathartic used in conjunction with other drugs as a laxative, found in the bundle sheath cells. The aloin content of Aloe barbadenis is approximately 30%, Aloe perryi approximately 25 to 28%, and Aloe ferrox is approximately 10%.

The pulp in the center of the leaf contains a mucilaginous portion yielding pure aloe gel (a virtually tasteless viscous hydrocolloid). The gel is of particular therapeutic interest. It contains primarily hexanoses and hexans, including arabinose, galactose and xylose. By far the greatest proportion of compounds found in the gel are these polysaccharides. Chemical analyses have also shown the gel to contain various carbohydrate polymers, notably either glucomannans or pectic acid.

The reputation of aloe vera comes primarily from its purported use as a wound healer. Aloe gel for personal use in the home is generally gotten by transversely cutting the leaves or "pups" of the aloe vera plant near the base, opening the leaves and extracting the clear gelatinous heart of the leaves. Care must be taken to cut away the very bitter yellow layer. Remaining clear gel is then used or applied topically as indicated. As an alternative, it is recommended once the fresh leaves are cut transversely, the leaf be left to stand for 18 hours so the bitter yellow substance can drain off. Enzymatic activity will be protected from oxidative destruction for this brief duration by the formation of a very fine layer at the site of the cut. Some experts believe the bitter yellow layer containing the aloin should be used as well.

However, most aloe vera products come from commercial sources. Since aloe gel is not very stable when exposed to air (beyond several hours) and thereafter begins to lose its effectiveness, many techniques have been developed to stabilize and preserve the gel. Stabilization techniques vary, but include gamma irradiation with radioactive cobalt, spray drying, freeze drying, short-time high temperature exposure, ultraviolet light exposure in the presence of a chemical catalyst, oxidation with hydrogen peroxide, the use of 0.0125% sodium benzoate (a derivative of benzoic acid) or Irish moss (due to its sodium and carrageenan content). Often these substances or methods of stabilization are combined. Some methods derive low concentrations of actual gel (i.e. ultraviolet light treatment). Any heat over 60 degrees C (140 degrees F), will break down vital enzymes in the gel. Yet these enzymes are responsible for the continued breakdown of the gel until it turns brown. A compromise to this problem is the use of interval high heat exposure for short periods of less than 3 minutes. This method will pasteurize the gel while reducing the loss of enzymatic activity.

Commercially prepared powdered aloe vera gels are also available. These can be produced by either spray drying or freeze drying pure aloe gel. The spray drying method requires heating the gel and removing the existing water under a vacuum. Some spray-dried aloe products have an added but inert material added to it making reconstitution difficult. In the freeze-dried method, the water is removed from the gel in the frozen state. Since this method lacks heat, it is more apt to retain the gel's enzymatic activity.

Aloe vera gel extract is not actually an extract but derived from pulverized, whole leaves.

Method of Action

Many of the active constituents of the aloe vera gel have been isolated and synthesized. Aloe vera is known to contain several pharmacologically active ingredients, including salicylates, a carboxypeptidase inactivating bradykinin in vitro and substances inhibiting thromboxane formation in vivo. The inhibition of thromboxane formation is important in the management of burns. Aloe vera seems to block the formation of vasoactive prostanoids, and therefore prevents the vasoconstriction, thrombosis and progressive ischemic necrosis in thermal and electrical burns associated with imbalanced production of thromboxane.

When tested alone on many types of bacteria, specific isolates from aloe vera have demonstrated poor bactericidal action. In contrast, the entire gel and aloe gel dermal extracts have been reported to have a good bactericidal effect on those same bacteria, suggesting whole gel is required for efficacy. The control of bacterial growth is essential in the management of burns or abrasive wounds.

It has also been established the moisturizing, emollient and healing properties of aloe vera gel are due to its polysaccharide constituents. The major polysaccharide is glucomannan. Other polysaccharides include uronic acid, pentose and galactose.

Two functionally- and chemically-distinct immunomodulatory compounds have been identified in the gel of aloe vera. These compounds have been shown in vitro to increase the activation of human complement and of human polymorphonuclear leucocytes (PMN).

Therapeutic Approaches

Therapeutic uses of aloe vera have been reported in the medical literature for over 50 years, and in the botanical and naturopathic literature for many more years.

Scientific studies exist supporting the antibacterial and antifungal effect of substances in aloe vera. Studies and case reports provide support for the use of aloe vera in the treatment of radiation ulcers and stasis ulcers in humans, and burn and frostbite injuries in experimental animals.

Modern clinical medical use of aloe began in the 1930's with reports of successful treatment of burns from X-rays and radium. These case studies were later confirmed in animal experiments and controlled clinical trials on humans. In one such experiment, 10 rabbits were subjected to 14,000 or 28,000 rep of beta radiation from strontium-90. Two of four areas were treated with aloe vera gel, the remaining two left untreated. Gross and microscopic morphological changes in the skin resulting from the radiation were compared in the treated and untreated areas. The aloe-treated areas consistently were completely healed within two months, whereas the untreated ulcerations remained four months later.

Dermatologists have shown considerable interest in aloe vera due its antimicrobial and antibacterial properties. In vitro studies, marked zones of inhibition (bacteriostatic activity) were shown for Staphylococcus aureus 209, E. coli, Streptococcus pyogenes, Corynebacterium xerose, Shigella paradysenteriae, Salmonella typhosa, Salmonella schotimuelleri, and Salmonella paratyphi.

In a study by Rodriquez-bigas et al (1988) using Hartley guinea pigs, wound bacterial counts were quantitatively measured and found to effectively be decreased equally by either 1% silver sulfadiazine (p=0.015) or aloe vera extract (p=0.015). The guinea pigs received full-thickness burns covering 3% of their body surface. The average time to complete healing in the control group was 50 days, while the aloe vera-treated animals healed by an average of 30 days (p < 0.02). Such data supports the belief aloe gel dermal extracts allow faster healing of burn wounds.

Aloe vera has also been shown to be of benefit in numerous studies on the healing of burns, frostbite and skin abrasion injury. Aloe vera ointments have been carefully and systematically tested for their efficacy on third degree burns. The process of gradual formation of the eschar has been followed in these experiments, examining the gross and microscopic changes that occur step by step. In one study, albino rabbits were given identical burns and found to benefit from an aloe vera gel called preparation S, which is a specially-prepared ointment with a base of 5% lanolin.

The efficacy of aloe vera gel vs. 1% silver sulfadiazine cream against experimental second-degree burns in guinea pigs was studied in a careful, quantitative, properly-controlled study. After 24-days, the silver sulfadiazine was found to be superior as measured by epithelialization, wound contraction, the thickness of formed granulation tissue and hair follicle count. Epithelialization on post-burn Day 8, Day 16, and Day 24 was significantly higher in the silver sulfadiazine-treated group. The authors concluded aloe vera gel hindered the healing process of the burn wounds when compared with 1% silver sulfadiazine cream. Whether these findings would be generalizable to human burns was not suggested, but the experiment has come to the attention of reconstructive surgeons.

Aloe vera has also been suggested in treatment of stasis, scalp disorders, leg ulcers, and peptic ulcers. In the case of peptic ulcer, the aloe parenchyma is separated from its cellulose matrix and emulsified with heavy liquid petroleum to minimize distaste at a dose of 2 to 2.5 fluid drams of the cellulose-free gel. Twelve patients with peptic ulcer, diagnosed by roentgenographic evidence of duodenal cap lesions, were treated with the aloe emulsion with encouraging results. No distress or further episodes were reported after one year of treatment. Although the mechanism of action is not fully understood, the aloe gel was found to inhibit the secretion of hydrochloric acid by the parietal cells of the stomach. Further, since the gel contains demulcents comprised of mannuronic and glucuronic units combining to form a polymer of high molecular weight, the uronic acids may have facilitated the healing of the ulcers by stripping toxic irritants.

In the treatment of leg ulcers, aloe vera gel is applied locally on ulcers three to five times a day as dressing, after preliminary cleansing of the lesion by simple washing with 1% citrimide in water, hydrogen peroxide solution, 3% boric acid lotion or sterile water. Gauze dressings are applied on the lesions after being soaked in aloe gel. Antibiotics are given when required to combat infections.

In leg ulcers sized 400 to 1400 mm2 persisting for many years, aloe gel is applied as described, and healing commences with epithelialization and proliferation of granulation tissue in the middle portion of the wound. The ulcer slowly decreases in size. In general, by Week 3 or 5, raised areas of granulation begin to appear with improved regeneration of the epithelium. The upper parts of the medial ulcer show creeping epithelialization and granulation at the edges. A few weeks thereafter, the lateral ulcer completely heals, forming a hard crust of greyish white color. The medial ulcer progresses well with advanced epithelialization of the edge. Healthy granulation tissue appears, showing adequate vascularization and a raised base. Finally, the crust is shed, leaving healthy skin which shows glazing.

Similar results have been seen with back ulcers, and in a man having a 5000 mm2 wound resulting from pseudoelephantiasis and a chronic leg ulcer secondary to venous statis and repeated recurrent thrombophlebitis and lymphangitis. It should, however, be mentioned in such clinical cases, patients do complain of increased pain at the start of treatment. The pain is probably due to improved circulation in the affected area rather than localized irritation. Aloe vera reportedly has nematicidal properties.

Toxicity Factors

For information on the toxicity of aloe vera products, refer to Aloe Vera Plant.

Aloe vera has not been reported to be a mutagen, fetotoxin or carcinogen. However, aloe is contraindicated in pregnancy and in individuals afflicted with hemorrhoids. Aloe vera can cause kidney irritation. The Handbook of Medicinal Herbs has given aloe the lowest ranking for toxicity among the herbs listed.

In an effort to discredit other producers of aloe in 1982, a competitor suggested carrageenan from Irish moss, used as a stabilizer by some producers, was "potentially carcinogenic."

This report was proven to be false. Carrageenan is currently accepted as a food additive throughout the world. It is approved under the U.S. Code of Federal Regulations (21 CFR 172.620) with no restriction.

Safety of carrageenan for human consumption has been thoroughly tested in extensive feeding studies using animals, including monkeys. The Joint Expert Committee of FAO/WHO has concluded carrageenan is safe and recommends an acceptable daily intake level in humans of up to 75 mg/kg/day.

The most recent review by the FDA in 1979 concluded commercial levels of carrageenan are safe and present no danger to the public's health.

Abstracts

References

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