Aloe Preparations

Aloe latex is prepared by cutting transversely the leaf near the base and kept in an inclined position so that the latex contained in the specialized pericyclic cells, and sometimes in the adjacent parenchyma, flows out in about 6 h. No pressure must be applied or the product will be contaminated with the mucilage present in the inner part of the leaves. The latex obtained is bitter and yellow condensed to dryness, it becomes a shiny mass, similar to broken glass, of a yellowish green to red-black color. Slow evaporation, carried out at an inappropriate temperature, yields an opaque mass with a waxlike fracture. The taste is nauseating and bitter, and the odor sour, recalling that of rhubarb, apple-tart, or iodoform (Sollmann, 1944). 

Aloe latex contains anthraquinones and is completely different from aloe gel, a colorless gelatin obtained from the central portion of the aloe leaf. The mucilaginous parenchymous tissue is excised from fresh leaves and immediately utilized for pharmaceutical preparations, or lyophilized and kept dry until use. During extraction of the gel, it is practically impossible to prevent contamination by the leaf latex as the leaves are cut. On the other hand, in intact leaves, anthraquinones may diffuse into gel from the bundle sheath cells. To reduce such contamination, the starting material must be from varieties of aloe with a reduced anthraquinone content. 

Scientific research has proved in recent years that the rind and the outer leaf, normally thrown away, contain much more active therapeutic ingredients. On the other hand, the gel is sensitive to heat and light, and can quickly deteriorate at high temperature. For these reasons, the gel is now available as a cold-processed extract obtained from aloe whole leaf. The fresh whole leaf is cut into small pieces and whipped to yield a homogeneous yellowish or reddish material. The product (10% aloe leaf and 90% water), concentrated, and in some cases deprived partially of aloins, is bitter. 

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POOH Odes, H. S., and Z. Madar. A doubleblind trial of a celandine. Aloe vera and psyllium laxative preparation in adult patients with constipation. Digestion... 

Chemists of India prepared both chlorides of mercury as early as the twelfth century (244). A detailed description of the process was given in the thirteenth or fourteenth century (245). A mixture of common salt, brick dust, alum, Indian aloe, and mercury was heated for three days in a closed earthen pot. The Japanese and Chinese also prepared calomel by similar methods (244). 

Alkali leach methods axe exemplified by the Bayer process for the preparation of pure a-A C for electrolysis (Section 17.5) from the mineral bauxite. Bauxite consists mainly of a-AlO(OH) (diaspore) and/or 7-A10(0H) (boehmite), the difference between these being essentially that the oxygen atoms form hep and ccp arrays, respectively. The chief contaminants are silica, some clay minerals, and iron(III) oxides/hydroxides, which impart a red-brown color to the mineral. Aluminum (III) is much more soluble than iron(III) or aluminosilicates in alkali, so that it can be leached out with aqueous NaOH (initially 10-15 mol L 1) at 165 °C under approximately 0.6 MPa pressure, leaving a red mud of iron (and other transition metal) oxides/hydroxides and aluminosilicates ... 

Gel preparation and crystallization is represented systematically using the Na 0—ALO,—SiO- —HjO system as an example. 

The family, characteristic of Arabia and South Africa with some species in other parts of Africa and Madagascar, has been separated from the Liliaceac. Species have been introduced elsewhere. Several have been used as a source of laxative anthraquinones and as a component of cosmetic preparations. Aloe is one of the oldest drugs. 

Aloe vera gel is a mucilaginous preparation obtained from the leaves of Aloe vera (syn. Aloe barbadensis) once the sap has been drained away. It is widely used in cosmetic products for its purported emollient and moisturizing effects. It is claimed to have antibacterial, antifungal, and anti-inflammatory properties and has been proposed as a potentially useful agent for radiation and thermal wounds (see Chapter 12). 

Another example of this is aloe, one of the few medicinal plants that has been a popular cure for a long time. Aloe latex is used for its laxative effect and should not be confused with aloe gel, used both in cosmetics and in ointments for skin ailments. Aloe whole leaf is another preparation taken internally as a drink for a wide range of human diseases including cancer, AIDS, ulcerative colitis, and other complaints. 

Almost everyone is familiar with aloe vera as a popular ingredient of skin lotion and suntan preparations. Its use for skin care and treatment goes back to ancient Mesopotamia, Egypt, and Greece. 

The word Aloe in pharmacopoeias and formularies means a drug derived from the dried leaf juice. This has always created confusion because the leaves of the genus Aloe are the source of two products that are quite different in their chemical composition and therapeutic properties aloe latex and aloe gel. These two products are obtained from two different specialized cells, latex from pericyclic cells and gel from parenchymatous cells. Therefore, the term juice must be avoided, as it could mean either the latex from the pericyclic cells or the gel after extraction from the leaf. However, to add to the confusion, there is also a preparation obtained from the whole leaf (total extract) and another obtained from the aloe wood, the so-called lignaloe or aloe of the Bible, a fragrant wood obtained from an entirely different plant that was once used as an incense (Capasso et al 1998). 

Experimental studies have also reported that aloe juice has antimetastatic activity and aloe extract inhibits induction of preneoplastic hepatocellular lesions. Antitumor effects of aloe extract may also depend on the ability to augment tumor-specific immunity. These findings have encouraged cancer treatment in humans with a preparation composed of aloe (5 years old) fresh leaf 300 g,... 

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