The aloe plant, being a cactus plant, is between 99 and 99.5 per cent water, with an average pH of 4.5. The remaining solid material contains over 75 different ingredients including vitamins, minerals, enzymes, sugars, anthraquinones or phenolic compounds, lignin, saponins, sterols, amino acids and salicylic acid. These are described in more detail below.
The plant contains many vitamins, excluding vitamin D but including the important antioxidant vitamins A, C and F. Vitamins B (thiamine), niacin, vitamin B2 (riboflavin), choline and folic acid are also present. Some authorities suggest that there is also a trace of vitamin B12 (Coats, 1979).
When taken orally, several of these biochemical catalysts, such as amylase and lipase, can aid digestion by breaking down fats and sugars. One important enzyme, a carboxypeptidase, inactivates bradykinins and produces an anti-inflammatory effect. During the inflammatory process, bradykinin produces pain associated with vasodilation and, therefore, its hydrolysis reduces these two components and produces an analgesic effect (Obata et al, 1993; Shelton, 1991).
Sodium, potassium, calcium, magnesium, manganese, copper, zinc, chromium and iron are all found in the aloe plant. Magnesium lactate inhibits histidine decarboxylase and prevents the formation of histamine from the amino acid histidine (Shelton, 1991). Histamine is released in many allergic reactions and causes intense itching and pain. The prevention of its formation may explain the antipruritic effect of aloe vera.
Sugars are derived from the mucilage layer of the plant under the rind, surrounding the inner parenchyma or gel. They form 25 per cent of the solid fraction and comprise both mono- and polysaccharides. By far the most important are the long chain polysaccharides, comprising glucose and mannose, known as the glucomannans (Beta-(1, 4)-linked acetylated mannan). When taken orally, some of these bind to receptor sites that line the gut and form a barrier, possibly helping to prevent "leaky gut syndrome." Others are ingested wholely by a method of cellular absorption known as pinocytosis. Unlike other sugars that are broken down prior to absorption, the polysaccharides are absorbed completely and appear in the blood stream unchanged. Here, they act as immunomodulators, capable of enhancing and retarding the immune response (Green, 1996; Kahlon et al, 1991; Sheets et al, 1991).
These phenolic compounds are found in the sap. The bitter aloes consist of free anthraquinones and their derivatives:Barbaloin-lO- (1151 — anhydroglucosyl) — aloe-emodin-9-anthrone)Anthrone-C-glycosides and chromones. In large amounts, these compounds exert a powerful purgative effect, but when smaller they appear to aid absorption from the gut, are potent antimicrobial agents (Lorenzetti et al. 1964; Sims et al, 1971a), and possess powerful analgesic effects. Topically, they can absorb ultra violet light, inhibit tyronase activity, reduce the formation of melanin and any tendency to hyper-pigmentation (McKeown, 1987; Strickland et al, 1993).
This woody substance, inert in itself, endows topical aloe preparations with their singular penetrative ability to carry other active ingredients deep into the skin to nourish the dermis (Coats, 1979).
These soapy substances form 3 per cent of the gel and are general cleansers, having antiseptic properties (Hirat and Suga, 1983).
These include Campesterol, f3 Sitosterol and Lupeol (Coats, 1979).
This is an aspirin-like compound possessing anti-inflammatory and antibacterial properties. Topically, it has a kerolytic effect, which helps to debride a wound of necrotic tissue.
These are the building blocks of proteins. Aloe vera gel provides 20 of the 22 necessary amino acids required by the human body and seven of the eight essential amino acids that the body cannot synthesise. These must be ingested in food.
It is surprising that the evident healing effects of aloe vera can be produced by such a small quantity of solid material. Some people believe that there is a synergistic action between all the component ingredients, giving a result which is greater than the sum of the individual actions.
The combined action of all herbal preparations taken from whole stems, roots, leaves or fruits containing huge numbers, but very small amounts of phytochemicals, stretches the boundaries of the conventional medicinal paradigm. In all allopathic (orthodox) medicine, the practice is to isolate, in a chemically pure form, the biologically active substance of the consitutent ingredients. These extracted drugs must be uniform in their composition in order to demonstrate a consistent physiological effect.
Perhaps there is some truth in an ancient Ayurvedic text from India: ‘Extracting drugs from a part of the plant is taking out the intelligence and throwing away the wisdom.’ Whole plant preparations, though less potent, are generally considered to be safer with fewer side effects.
The evidence suggests that the primary sites of action for aloe vera are:
Aloe vera can be taken internally as a drink or applied topically. The principle ingredient of any product should be the stabilised aloe vera gel which is as near to the inner gel of the natural plant as possible. It must not, therefore, be treated with excessive heat or filtered during the manufacturing process, as this destroys or reduces the effect of certain essential compounds, such as the enzymes and polysaccharides. Regrettably there are many products which contain virtually no aloe and yet are marketed as though they do. Caution applies particularly to cheap capsules of dried aloe leaf.
Not only does aloe vera provide nutrition and produce an anti-inflammatory action, it also has a wide range of antimicrobial activity. In-vitro experiments have been carried out on numerous organisms and have regularly shown that, in normal strength, aloe vera is either bactericidal or bacteriostatic against a number of common wound pathogens.