Aloe

Most commonly used species are Aloe ferox Mill., A. perryi Baker, and A barbandensis Mill. Also called A. vera Tournefort ex Linne or A. vulgaris Lamark.  Liliaceae.  The common name is aloe or aloe vera.

Aloe use goes back to the Mesopotamians and Egyptians, being used for treating the skin and for its laxative properties.  It is mentioned by the Greek physician, Dioscorides in 74 AD.  It was in the U.S. Pharmacopoeia in 1820, primarily for its cathartic effects.  The current interest in aloe began in the 1930s when researchers  found it helpful for healing wounds caused by x-rays, ultraviolet and gamma rays.  It caught popular commercial interest in the 1970s and has exploded into popularity since then.

There are more than 360 species of aloe, which are perennial succulents, primarily native to Africa.  The fleshy leaves, arranged in a rosette configuration, are triangular and stiff with thorny ridges.  Being succulents, they are filled with a mucilaginous pulp.  Just beneath the skin, the peripheral bundle sheath cells have a bitter, yellow exudate when cut.  The leaves can be 1 ½ to 4 feet long.  They are cultivated in the Caribbean, Mediterranean, Japan and America.

The whole leaf or only the inner gel of the succulent leaf is used.  The dried latex is approved by the FDA for use as a cathartic.  It is commercially available as dried aloe, topical gels, cosmetic products and beverage drinks.  It is easily grown as a houseplant and a leaf simply cut off, split open and applied to burns.

There are two separate products extracted from the leaves of the aloe plants.  There is a yellow, bitter juice from the leaf epidermis that is the source of the laxative drug aloe, and a clear gel from the center of the leaves that is used to relieve burns and wounds.

The bitter yellow latex is processed into the crystalline form of aloin, which contains up to 25% barbaloin, the main active laxative compound.¹  This is used extensively as an active ingredient in commercial laxative preparations, most often in combination with other botanical laxatives such as cascara and senna.  Despite its widespread use, the drugs aloe and aloin are considered the least desirable of the plant laxatives for home health care.  It is considered a drastic cathartic, the strong purgative effects are caused by aloinosides irritation of the large intestine.

The gel is one of the most widely used herbal remedies in the United States to relieve burns, sunburns, to promote wound healing and as a skin moisturizer and softener.  This product is usually free of the anthraquinone glycosides.  Most studies have generally found aloe gel to accelerate healing.  Burn wounds in guinea pigs healed significantly faster with aloe gel that those treated with silver sulfadiazine.²  The glycosaminoglycan components of the matrix in a healing wound were found to be higher in wounds treated with aloe, in particular, hyaluronic acid and dermatan sulphate levels were increased.³  Increased capillary perfusion has been observed after applying aloe to the skin.  The Food and Drug Administration has approved Aloe vera for the treatment of inflammation.⁴  Aloe has been shown to delay wound healing in some cases of surgical wounds such those produced from laparotomy or cesarean delivery.  It is suggest therefore, that topical aloe preparations are not useful for treating deep vertical wounds.

The antibacterial and antiviral activity of aloe has been studied, but has yielded conflicting results. It has shown to have activity against many common bacteria, fungi and viruses.  Different studies have different results, however.  This could be as a result of using different varieties of aloe and different means of extraction of the gel.

Aloe juice products are widely available for internal use and are considered helpful in healing many types of gastrointestinal irritation.  Preliminary and anecdotal studies indicate that it my have “tonic” and anti-ulcer effects on the gastrointestinal tract.  There are a variety of methods used to process and stabilize these products, with quite a difference in results.  The primary ways are distillation, freeze-drying, cold processing and heat processing.  The heat processing appearing to be the most effective for stabilizing and retaining the significant components of the aloe.⁵

The leaf of aloe contains about 99% water and only 1% solids.  These solids contain more than seventy-five chemical compounds.  The cathartic principle is from several anthraquinones, the primary ones being aloin and barbaloin.  It contains glycoproteins, mucopolysaccharides and polysaccharides, which are being studied for their emollient effect and antiviral and immunopotentiating properties.  It also contains tannins, organic acids, enzymes, vitamin, steroids and prostanoid compounds.  The chemical composition differs among species and the time of harvest.⁶

The dosage for products containing the leaf latex, and used as a laxative is 20-30 mg hydroxyanthrancene derivatives a day, calculated as anhydrous aloin; or the smallest dosage necessary to maintain a soft stool.⁷  The optimal dose for beverage type products is not known., but it is recommended that no more than one quart be consumed in one day, and that would be considered excessive.

Stimulant laxatives should not be used for more than one or two weeks without medical advice.  A harmless red color may appear in the urine during the course of treatment.⁸  The use of aloe as a laxative should not be used in pregnancy and lactation.  It should also not be used as a laxative by those with ulcerative colitis, Crohn’s disease, inflamed hemorrhoids, intestinal obstruction and kidney disorders.⁹

Using aloe as a laxative can cause severe cramping.  Long-term use can cause disturbances of electrolyte balance, particularly potassium. Chronic use, and the resulting loss of potassium may increase the effectiveness of cardiac glycosides, as well as have an effect on anti-arrhythmic agents.  The gel used topically has occasionally caused contact dermatitis and burning to dermabraded skin.