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AGAVACEAE
(Agave or Century Plant family)
• Medicinal / Folk-medicinal aspects: Folk-medicinal uses as externally-applied remedies of the prepared leaf, the fresh juice, the concentrated sap, and a polysaccharide gum that exudes from the leaves and roots have been documented for certain Agave species. Most of the uses are as might be expected for plants with irritant properties. • Members of the family Agavaceae occur naturally in tropical and arid regions. Many have leathery-succulent leaves. Until recently, the family Agavaceae included about 670 species in 20 genera (Willis 1973). Taxonomic revision has reduced the family progressively to 210 species in 13 genera (Mabberley 1997), the principal genus Agave L. accounting for about 100 species. Genera formerly considered to belong to the Agavaceae have been moved to the Asparagaceae and Asphodelaceae. Some authorities continue to regard the agaves as members of the Amaryllidaceae. Many are to be found in cultivation. Several species, including Agave fourcroydes Lemaire, Agave sisalana Perrine, and several Furcraea Vent. and Yucca L. species yield useful fibre. Others are grown as indoor or outdoor ornamentals, or in collections of succulent plants. Mezcal (or mescal), the popular liquor of Mexico, is a brandy distilled from the fermented mash of the cooked stems of certain wild and cultivated Agave L. species, especially Agave tequilana F.Weber (from which the mezcal known as tequila is produced), Agave pacifica Trel., and Agave palmeri Engelm. The abundant sap obtained after cutting off the young flower buds of Agave atrovirens Karw. ex Salm-Dyck (syn. Agave salmiana Otto ex Salm-Dyck subsp. salmiana) and possibly other species is fermented to produce an alcoholic beverage known as pulque from which mezcal may also be distilled (Purseglove 1972, Bahre & Bradbury 1980, Cedeño C 1995). Hecogenin, which is released by hydrolysis from the steroidal saponins of Agave sisalana, and sarsapogenin, which is similarly obtained from Yucca brevifolia Engelm., have been utilised as precursors in the production of medicinally-used steroids (Dewick 1997). Many species have needle-sharp leaf-tips that are capable of inflicting mechanical injury (Oakes & Butcher 1962, Borup et al. 2003). The edges of the leaves of many species are also armed with thorns capable of inflicting mechanical injury. The following species are representative:
In Indian traditional medicine, the fresh juice of this plant is regarded as a good external application to bruises and contusions. The large fleshy leaves, when cut into slices, may also be used as a poultice, whilst the gum exuding from the leaves and root is used as a cure for toothache (Nadkarni 1976). Viegi et al. (2003) recorded that Agave americana is used for the treatment of skin problems in folk veterinary medicine in Italy. Anon (1905) reported that the sap or juice from a large Agave americana that a gardener and his assistants cut down using a small axe caused intense irritation of the hands. One of the assistants, who had incautiously rubbed his face and neck with his hand, suffered severely for a short time. This report was referred to by Maiden (1909b) and is probably the origin of subsequent references to the irritancy of this plant by Schwartz et al. (1957), McCord (1962), Watt & Breyer-Brandwijk (1962), and Behl et al. (1966). Dorsey (1962) noted that he has seen a case of dermatitis caused by a "century plant". No further detail was provided. Souder (1963) listed this species as a plant containing saponin and stinging crystals of calcium oxalate. These crystals of calcium oxalate are in the form of raphides without barbs or grooves, and are of a length [~200 µm] that is associated with a capacity to irritate the skin (Sakai et al. 1984). In addition, proteases present in the leaf (Du Toit 1976) are likely to contribute (along with the saponins) to the micro-trauma produced by the needle crystals of calcium oxalate when they penetrate the skin (see also, for example, Dieffenbachia seguine Schott, fam. Araceae). The use of a "cactus-juice" shampoo derived from this species caused dermatitis (Kerner et al. 1973); an open epicutaneous test with the sap produced contact urticaria followed by eczematous dermatitis. Closed patch tests produced severe reactions. Papulovesicular dermatitis in a series of 12 patients over a 4 month period was investigated by Brenner et al. (1998). Golan et al. (2000) reported a further similar case. The irritation had been caused by intentional exposure to the juice from the lower leaves of the plant, which had been vigorously rubbed onto the skin by the patients themselves who were soldiers seeking sick leave. The reactions were characterised by sudden onset and extreme itchiness. Several of these malingerers also complained of systemic symptoms including sore throat, headache, diarrhoea, or myalgia. Erythematous dermatitis was again reported by High (2003), who described a case that resulted from spattering of plant sap when the fleshy leaves were cut using a mechanical trimmer. Ricks et al. (1999) and Cherpelis & Fenske (2000) reported purpuric reactions in which systemic symptoms were also a feature. Crawford et al. (2003) provide a dermatologic cameo on Agave americana. According to Remington et al. (1918), the leaves of Agave americana are said to be used as counter-irritants. The skin of the leaf has also been described as irritant and has been used in parts of Africa as a rubefacient in rheumatism; the heated and split leaf has been applied for the same purpose (Watt & Breyer-Brandwijk 1962). The plant bears spine-tipped leaves that are capable of inflicting mechanical injury. According to Morton (1971), the sap of Agave picta is said to be particularly irritant, causing a burning rash. [Information available but not yet included in database] [Information available but not yet included in database] [Information available but not yet included in database] [Information available but not yet included in database] [Information available but not yet included in database] This plant has been grown extensively in Yucatán in eastern Mexico for the commercial production of a fibre known as henequén, which resembles sisal [see Agave sisalana Perrine ex Engelm. below]. Souder (1963) included Agave fourcroydes in a list of plants containing saponin and stinging crystals of calcium oxalate. However, Schwartz et al. (1957) noted that the leaves of the "henequin" plant which grows in Yucatán (and which they identified, perhaps erroneously, as the source of sisal) do not seem to contain any skin irritants. This species yields a commercially important fibre known variously as lechuguilla, istle, ixtle, Mexican fibre, or tampico. Schwartz et al. (1957) included this species in a list of irritant plants. In south-western United States and Mexico, ingestion (mainly during times of drought) of Agave lecheguilla has given rise in goats and sheep to photodermatitis accompanied by hepatic and renal damage. The condition is known as "swell-head" (Mathews 1938a, Mathews 1938b). Deposition of steroidal sapogenins in the bile ducts of affected animals is a feature of the toxicosis (Camp et al. 1988). The plant is used as a vesicant in Mexico (Díaz 1976). [Information available but not yet included in database]
In northern Morocco, the juice from the leaves of this species is used in folk medicine as a wash for skin diseases (El-Hilaly et al. 2003). This species yields a commercially important fibre known variously as sisal, sisal hemp, or Bahama hemp. According to McCord (1962), dermatitis is frequent in commercial sisal production. The raw sap of the plant is corrosive to metal and highly irritating to the eyes and skin. It causes an instant, stinging red rash in gardeners who have occasion to cut any part of the plant; it also affects factory workers exposed to the sap and the wet fibre in the process of extraction. The odour of sisal in mattresses, generally in combination with some other material, causes allergic reactions in sensitive individuals (Wilcox & McGeorge 1912). Kerner et al. (1973) also recorded that sap from this species has been found to have irritant properties. By contrast, Bhalme & Pasricha (1986) observed that the freshly exposed pulp of Agave sisalana, when rubbed 10 times on the forearms of 10 volunteers, produced a transient itching and burning in only one individual. Further, Bhalme & Pasricha (1986) observed delayed positive reactions in 2 out of 10 volunteers whom they patch tested with the pulped leaf of this plant, whilst positive patch test reactions to sisal have been reported by Poljacki et al. (1993). An occupational dermatosis caused by mouldy sisal was described by Faninger & Markovic-Brisk (1960). [Information available but not yet included in database] Sap from this species has been found to have irritant properties (Kerner et al. 1973). Morton (1981) noted that the juice is irritant, causing an instant rash and stinging of the skin. Souder (1963) listed Agave vivipara as a plant containing saponin and stinging crystals of calcium oxalate.
[Information available but not yet included in database]
In traditional Chinese medicine, this plant provides the crude drugs Herba Hostae Plantagineae, Flos Hostae Plantagineae, and Radix Hostae Plantagineae. The expressed juice from the root of Funkia subcordata (yu zan hua 玉簪花; bai he xian 白鶴仙) is considered to be a counter poison to infectious abscesses and cancerous sores; the bruised leaves are applied in insect bites; and the flowers (from which a fragrant oil may be distilled for use as a perfume) are added to prescriptions for the treatment of skin diseases and wounds (Stuart 1911). The plant is cultivated for its fragrant flowers, from which tuberose absolute and other fragrance raw materials are prepared (Arctander 1960). Souder (1963) included this species in a list of agaves containing saponin and stinging crystals of calcium oxalate. The spines of Yucca species can cause injury to grazing cattle (Migaki et al. 1969). Eye injury has been caused by the short black spine at the leaf tip (Morton 1977). Kanerva et al. (2001) observed positive skin prick tests to this plant in two individuals who presented with occupational contact urticaria. In a further series of 600 patients, positive prick test reactions were observed in about 6% of those tested. [Information available but not yet included in database] Referring to Yucca elephantipes, Dahlgren & Standley (1944) note that the plant bears spine-tipped leaves. References
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