Candelabra Aloe, Tree Aloe, Mountain Bush Aloe

Aloe arborescens

Physical Characteristics

Aloe arborescens is an evergreen Shrub growing to 3 m (9ft) by 2 m (6ft) at a medium rate. See above for USDA hardiness. It is hardy to UK zone 10 and is frost tender. The flowers are pollinated by Sunbirds, Bees. The plant is not self-fertile. It is noted for attracting wildlife. Suitable for: light (sandy) and medium (loamy) soils, prefers well-drained soil and can grow in nutritionally poor soil. Suitable pH: mildly acid, neutral and basic (mildly alkaline) soils and can grow in very acid soils. It can grow in semi-shade (light woodland) or no shade. It prefers dry or moist soil and can tolerate drought.

Distribution

Eastern and southern Africa - Malawi, Zimbabwe, Mozambique, Botswana, S. Africa.

Habitats

Edible Uses

Edible Parts: Leaves Nectar Stem Edible Uses: The flowers are sucked for their sweet nectar[ 301 ]. In Japan the leaves are used as a vegetable and as a health food because they are thought to overcome constipation. Parts of the stem with a number of leaves attached are marketed as a vegetable[ 299 ]. The plant is an important ingredient of 'Kidachi aloe candies', a popular sweet in Japan, enjoyed for its tangy yoghurt flavour[ 299 ].

Medicinal Uses

Antiinflammatory Cancer Hypoglycaemic Laxative Purgative Skin This species is one of the main sources of Aloe for medicinal use - preparations made from it are sold as over-the-counter drugs for the acceleration of gastric secretion, as a purgative and for dermatological use[ 299 ]. In Ecuador, where the plant is cultivated, it is considered the first treatment for any type of scratch, bite, or burn, and is used in hospitals as a primary treatment for burns up to the third degree[ 372 ]. Worldwide attention was drawn to the possible value of the gel prepared from this and other Aloe species after the second World War, when skin burns of victims of the nuclear bombs on Japan were successfully treated with it[ 299 ]. The gel of this species contains much higher concentrations of the primary compounds present in other aloes, and this higher concentration is responsible for the faster and more effective action of the gel against skin conditions[ 372 ]. As in most Aloe species, the leaf exudate of this species contains anthraquinone derivatives such as aloin and hydroxyaloins[ 299 ]. Although aloin is inactive as a laxative, it is activated in the digestive tract by Eubacterium species to the compound aloe-emodin anthrone, which is an effective laxative[ 299 ]. Although some observations indicate that in diarrhoea induced by aloin, increased water content might be more important than stimulated peristalsis, the side effects of prolonged use point to a griping effect on the colon. Therefore, aloin should preferably be administered in combination with an antispasmodic to moderate its griping action[ 299 ]. In any case, anthraquinone laxatives should not be used for longer than 8 - 10 days, or by children younger than 12 years. Contra-indications also include pregnancy, breastfeeding, intestinal inflammations and haemorrhoids[ 299 ]. Possible side effects of aloin include congestion and irritation of the pelvic organs. Anthraquinone laxatives may play a role in development of colorectal cancer as they have genotoxic potential and also tumorigenic potential in rodents[ 299 ]. It has been claimed that aloin is also responsible for antihistamine and anti-inflammatory activity[ 299 ]. Both aloin and aloeresin B have skin-whitening activity[ 299 ]. The gel contains polysaccharides and glycoproteins. Apart from mannan and glucomannan, arboran A and arboran B have been identified, which have hypoglycaemic effects. The structure-function relationship of polysaccharides from gel from different Aloe species is still subject to research. Biological activity is thought to be, at least partly, due to immunomodulating effects of these polysaccharides[ 299 ]. The leaf epidermis contains lectins (aloctin A and aloctin B) that inhibit the growth of fibrosarcoma in animals. The leaf powder showed protective effects against human carcinogenesis[ 299 ]. In 2002 the United States Food and Drug Administration withdrew the 'generally recognized as safe and effective (GRASE)' status for over-the-counter drugs based on aloe exudates[ 299 ]. Aloe arborescens gel works as a synergist of neomycin sulphate in eye drops; they are useful in the treatment of inflammation and infections of the eye[ 299 ]. Freeze-dried leaves have shown a 70% growth inhibition of Trichophyton mentagrophytes (one of the fungi causing athlete?s foot in humans)[ 299 ]. A leaf decoction is given to women to ease childbirth[ 299 ]. The leaves are eaten as a vegetable as a treatment for constipation[ 299 ]. The split or crushed fresh leaves are widely used to treat burns and wounds[ 299 ].

Known Hazards

The sap of Aloe species contains anthraquinones. These compounds have several beneficial medicinal actions, particularly as a laxative, and many species of Aloe are thus employed in traditional medicine. Whilst safe in small doses and for short periods of time, anthraquinones do have potential problems if used in excess. These include congestion and irritation of the pelvic organs[ 299 ]. Long term use of anthraquinone laxatives may also play a role in development of colorectal cancer as they have genotoxic potential, and tumorigenic potential[ 299 ].