Aloes is the dried juice of the leaves of Aloes barbadensis Miller, known as Curacao aloes; or of Aloe perryi Baker, known as Socotrine aloes; or of Aloe ferox Miller and hybrids of this species with Aloe Africana Miller and Aloe spicata Baker, known as Cape aloes, belonging to family Liliaceae.
Aloes is indigenous to eastern and southern Africa and grown in Camp colony, Zanzibar and islands of Socotra. It is also cultivated in Caribbean islands, Europe and many parts of India, including North West Himalayan region.
The word aloes has originated from an Arabic word viz. Alloch meaning a shining bitter substance. Among the different species, ‘vera’ means true, ‘ferox’ means wild, ‘spicata’ refers to flowers in spikes, and ‘barbadensis’ and ‘africana’ refer to habitant of the plant. Among the folklore uses, it has been reported that in Congo region of Africa, the natives used to rub the mucilage of leaves for reducing perspiration and masking of human odour, thereby offering protection from wild animals. It is also known that Aloe barbadensis was used along with burnt alum for healing sore eyes.
The genus Aloe consists of about 200 species, some of which are used as sources of Aloes. These plants have rosettes of subulate, succulent large leaves. The leaves are sessile and a strong spine at apex and also number of spines along the margins. The lower portion is rounded and upper portion is slightly concave.
For the cultivation, root suckers are used for propagation. The plants grow even in poor grades of soil and in dry climatic conditions. The root suckers are planted in the rows about 50 c, apart. Water logging near the plant must be prevented. The roots do not penetrate much in the soil. For the purpose of manure, a mixture of nitrogen, potassium and phosphorus is used. The leaves are cut for for the first instance in second year of cultivation and the drug is obtained from leaves for twelve years. After twelve years, the plants are completely harvested by uprooting and once again the land is worked for replantation. During the collection of leaves, a cut is given to leaves near their bases, by which the juice located in parenchymatous cells of pericycle exudes out, due to the pressure exerted by mucilage cells. A single incision is sufficient for drawing out all the juice from entire system of pericyclic cells. The preparation of various type of aloes is outlined here.
The original of the Zanzibar oleos is not correctly known and sometimes, it is also regarded simply as a variety of Socotrine aloe. The juice is poured into skins of some small carnivorous animals, where it solidifies and as such packed in wooden boxes. Zanzibar aloe is also sometimes, called as monkey-skin aloe, although the skin is not that of monkeys.
Zanzibar aloes show a liver brown color with a dull, waxy, smooth and even fracture. It has a characteristic but not much disagreeable odor and a bitter taste.
Zanzibar aloes exhibits irregular lumps in which modular masses are embedded.
All the varieties of aloe are the major sources of anthraquinone glycosides. The principal active composition of aloe is aloin, which is mixture of glycosides, among which barbaloin is the chief constituent. It is chemically aloe-emodin anthrone C-10 glucosides and it is water soluble.
Barbaloin is a C-glycosides and it is not hydrolysed by heating with dilute acids or alkalis. Ferric chloride decomposes barbaloin by oxidative hydrolysis into aloe-emodin-enthrone, little aloe-emodin and glucose.
Along with barbaloin, aloes also contains isobarbaloin, β-barbaloin,aloe-emodin and resins.
The drug also contains aloetic acid, homonataloin, aloesone, chrysophalic acid, chrysamminic acid, galactouronic acid, choline, choline salicylate, saponins, mucopolysaccharides, glucosamines, hexuronic acid, caniferyl alcohol, etc.
The amount of barbaloin in different commercial varieties varies to a large extent.
The resin of aloe principally contains Aloesin. It is a type of a C-glucosyl chromome. Aloes is also responsible for purgative action of aloes.
Aloes is used as a purgative. Its effect is mainly on colon. It has a stronger purgative action in the series of all crude drugs with anthracene glycosidal content. The counter effect the gripping action, it is given with carminatives.
Aloin is preferred now-a-days to aloes, both of which are official. Besides purgative property, aloes enjoys many other uses. It is an ingredient of compound tincture of benzoin(Friar’s balsam).
Aloe gel, formed in inner parenchymal cells of the leaf, is a slightly viscous and clear liquid. During collection, it should not get contaminated with aloe juice. Such gel is used in topical therapeutic applications and also in many cosmetic products, but the therapeutic value, if taken orally, is questionable. The gel possesses good moisturizing properties and also has formulation role for oil in water(approved by U.S.F.D.A) preparation. It show anti-inflammatory properties due to the chemical contents like salicylates, carboxypeptidases(inactive bradykinen) and magnesium lactate(interfering with the conversion of histidine to histamine in the mast cells). The polysaccharides and sugar content have the role for hydrocolloid dressing and also osmotic bactericides. Aloe gel also increases the removal of dead tissue due to its Aloctine-A content which stimulates macrophage production. It is believed that only fresh gel probably has a role in treatment of burns and wounds.
It is also used in the treatment of pains and itching and also to slow down ulceration and keratosis, Aloe gel is used in skin cosmetics as a protective due to its antiwrinkle properties. Aloe is also used externally for painful inflammation.