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(Umbellifer or Carrot family)
- Centella L.
This is a genus of about 50 species found mostly in South Africa, with Centella asiatica Urban being distributed pantropically (Mabberley 2008). Centella L. species have similarities with Hydrocotyle L. species and have previously been classified by some authorities in a distinct family, namely the Hydrocotylaceae (see Willis 1973). Following upon the work of the Angiosperm Phylogeny Group (2003), the genus Centella L. was moved into the Mackinlayaceae, but then was restored to the Umbelliferae by Plunkett et al. (2004).
- Centella asiatica Urban
- (syns Hydrocotyle biflora P. Vell., Hydrocotyle asiatica L., Hydrocotyle erecta L.f., Centella biflora Nannf., Centella coriacea Nannf., Centella erecta Fern.)
- Asian Pennywort, Indian Pennywort, Asiatischer Wassernabel, Bevilacque
The plant is well known to practitioners of Indian and Chinese traditional medicine. In India it is known as brahmi. In China, a preparation of the root (Hydrocotyle Asiatica Radix or Centella Asiatica Radix) is known as Gotu Kola; the dried whole plant (Herba Centella Asiatica) is known variously as Beng Da Wan, Han Ke Cao, Ji Xue Cao, Luo De Da, and by other names.
According to Waring (1883), to whom Piffard (1881) referred, Hydrocotyle asiatica has gained considerable repute as a remedy for leprosy. The dried and powdered leaves are sprinkled on the ulcers (and also taken orally), or alternatively the fresh bruised leaves may be applied. The remedy causes great itching of the skin over the whole body, when its use should be discontinued. Nadkarni (1976) similarly noted that preparations of the plant are highly valued remedies in Indian traditional medicine, being administered both internally and externally for a variety of skin diseases including ulcers (chronic, scrofulous, syphilitic), chronic eczema, psoriasis, leprosy, elephantiasis, and abscesses.
The juice of the leaves or whole plant is said to be excellent for stopping the irritation caused by prickly heat (Hurst 1942). According to Perry & Metzger (1980), the uses of Centella asiatica over all its eastern range are many and very much alike in different regions.
Sachs et al. (2002) noted that this species is used by the people of Ngada on Flores (an Indonesian Island) for treating wounds. The wound healing activity of the plant appears to be attributable to its content of asiaticoside, asiatic acid, and madecassic acid (Maquart et al. 1990, Bonte et al. 1994, Bonte et al. 1995, Maquart et al. 1999, Shukla et al. 1999a, Shukla et al. 1999b) through stimulation of collagen and glycosaminoglycan synthesis.
The plant has also been studied as a topical antipsoriatic by Natarajan & Paily (1973). Using keratinocyte cultures, Sampson et al. (2001) found that an aqueous extract of the plant exhibited antiproliferant activity that could support its use as an antipsoriatic. The activity was attributed to madecassoside and asiaticoside.
Interestingly, asiaticoside was shown to inhibit healing of experimental corneal wounds in rabbits (Callizo et al. 1996). Studies of the effect of asiaticoside in corneal wounds and ulcers have been documented by Abou Shousa & Khalil (1967) and by Mekkawi (1968).
Asiaticoside appears also to be able to inhibit collagen production in such a way as to inhibit formation of hypertrophic scars, keloids, and stretch marks (striae gravidarum / striae distensae) (Bosse et al. 1979, Qi et al. 2000, Widgerow et al. 2000, Young & Jewell 2003).
Extracts from the plant have been formulated into several commercial products including Collaven™, Emdecassol™, Madecassol™, Centelase™, Marticassol™, Blastoestimulina™, and Trofolastin™. Reports of allergic contact dermatitis, confirmed by patch testing have appeared sporadically following topical use of Madecassol™, (Eun & Lee 1985), Centelase™ (Santucci et al. 1985, Vena & Angelini 1986, Danese et al. 1994), and Blastoestimulina™ (Izu et al. 1992, Aguirre et al. 1993, Bilbao et al. 1995, Gonzalo Garijo et al. 1996). Asiaticoside, asiatic acid, and madecassic acid appear to be the sensitisers (Huriez & Martin 1969, Hausen 1993). The possibility of sensitivity to other components of the formulations (for example, propylene glycol) should not be overlooked (Eun & Lee 1985, Hausen 1993).
It is pertinent to note that the phytochemical literature dating back over 50 years appears to show that the asiaticoside content of Centella asiatica varies with geographical source (Watt & Breyer-Brandwijk 1962, Oliver-Bever 1986), suggesting the existence of chemovars. The significance of this observation with regard to the various biological activities ascribed to the plant remains to be determined.
Hausen (1993) provides a detailed review of the many dermatological uses of Indian pennywort and also a review of the several cases of contact allergy reported following the use of commercial products containing an extract of the plant. He concludes that the low incidence of reports of contact dermatitis in relation to the widespread use of products containing an extract of the plant suggests that the plant is only a very weak sensitiser. Studies in guinea pigs supported this assessment, showing that asiaticoside, asiatic acid, and madecassic acid were all very weak sensitisers.
- Cnidium dubium
These species yield linear furanocoumarins (Nielsen 1971).
- Cnidium monnieri Cusson ex Juss.
- (syns Cicuta monnieri Crantz, Ligusticum monnieri Calest., Selinum monnieri L.)
- Monnier's Snowparsley
These species yield linear furanocoumarins (Nielsen 1971).
- Conium maculatum L.
- Poison Hemlock, Carrot Fern
Dermatitis from the plant was reported by several authors cited by Touton (1932). Massey (1941) and Hardin & Arena (1974) list the plant as capable of producing dermatitis. The plant yields two linear furanocoumarins (Nielsen 1971). The plant is sometimes sold as an ornamental under the name of California fern (Massey 1941). Application of the plant to the skin produces a burning feeling followed by paralysis of sensation (Piffard 1881).
- Coriandrum sativum
The fruits provide coriander seeds used in flavouring. The seeds were found in Egyptian tombs of 960-880 B.C. and the plant was recorded in the medical Papyrus of Thebes in 1552 B.C. Loveman (1938) observed a positive patch test reaction to Oil of Coriander. Oil of Coriander is considered to be a known allergen and therefore has been removed from certain brand-name cosmetics (Anon 1973).
- Cuminum cyminum
The seeds were used as a condiment by the Ancient Greeks and in the Middle Ages. Oil of cumin used in perfumery is said to have some of the properties of other essential oils but has not been implicated in dermatitis (Greenberg and Lester 1954). Distinct phototoxic effects were reported for undiluted cumin oil but none from its principal ingredient, cuminaldehyde (Opdyke 1974).
60 species are found in Europe, Africa, Asia and America. The fruits are burred and adhere to animals. D. carota is the wild carrot.
- Daucus carota var sativa
The plant is more or less bristly, bearing stiff strong hairs. The volatile oil contained in the leaves and fruits varies greatly from one kind of carrot to another (Burkill 1935, Watt & Breyer-Brandwijk 1962). Pammel (1911) reported that handling the foliage of carrots, especially when wet, produced irritation, even vesication, in some persons. Prolonged exposure to carrots in canning factories can produce irritation of the skin and mechanical injury from the hairs (Peck et al. 1944). In seven cases of occupational dermatitis from carrots, the eruption was localised to the hands in five cases but in two cases the forearms, neck and face were also affected (Vickers 1941). Peck et al. (1944) described acute or chronic dermatitis affecting the hands and forearms and in some persons, the neck and face. 15 of 17 persons showed positive patch test reactions to slices of raw carrot. Aqueous extracts of carrot, the dried residue of this extract, ether and acetone extracts, carrot juice and heated carrot produced positive patch test reactions.
Allergic contact dermatitis from carrots was reported by Klauder and Kimmich (1956) affecting 13 employees in a food-processing plant. The incubation period was usually about two weeks. Vesicular dermatitis affected the fingers and dorsa of the hands. All 13 patients showed positive patch test reactions to carrot slices, stronger to the cut surface than to the outer intact surface. In one of two patients tested, boiled carrot produced a positive reaction.
Two of 77 (Peck et al. 1944) and three of 55 controls (Vickers 1941) showed irritant reactions to raw carrot slices.
Cross-sensitivity was observed to parsnip (Pastinaca) and celery (Apium); negative reactions were observed to some other umbelliferous plants (Klauder and Kimmich 1956). Dermatitis from carrots is an industrial problem (Henry 1933, Vickers 1941, Peck et al. 1944, Klauder and Kimmich 1956) but is considered significant in housewife's eczema (Shelmire 1940, Agrup 1969).
Spitzer (1937) observed a case of meadow dermatitis; besides the erythema there was an exact copy of a leaf of wild carrot (D. carota) on the skin of the patient who had lain undressed in a meadow; he considered this copy of a leaf to be due to mechanical irritation by hairs of the plant. Vickers (1941) suggested a photosensitising effect of carrots. Extracts of the plant had a weak phototoxic activity (Van Dijk and Berrens 1964). Pathak (1975) lists the plant as implicated in causing phytophotodermatitis. Carrots have been reported to cause contact urticaria (Urbach and Gottleib 1949). Oil of carrot seed has been suspected as an agent of contact dermatitis (Greenberg and Lester 1954, Klarmann 1958). Contact sensitivity to carotene is noted under Citrus.
- Echinophora L.
Ten species are found around the Mediterranean region (Mabberley 1987). The plants are characterised by their spiny flowering parts.
- Echinophora spinosa L.
The plant is a very spiny, much-branched perennial, the leaves, calyx, bracts, and bracteoles of which being spine-tipped. It is found growing in sand by the sea in Mediterranean Europe (Polunin 1969).
- Ferula communis
- (syn. Ferula abyssinica)
The root contains a toxic principle which, like dicoumarol from Trifolium, leads to lowering of the prothrombin level of the blood and haemorrhages in animals who ingest the plant (Verdcourt and Trump 1969).
- Ferula galbaniflua
- Ferula rubicaulis
These species are sources of medicinal Gum Galbanum which is rubefacient and irritant to tender skin (Dioscorides 1st Cent. A.D., Dispensatory 1884, Piffard 1881). Three of 15 individuals who were contact sensitive to balsam of Peru (from Myroxylon balsamum Harms, fam. Leguminosae) showed positive patch test reactions to galbanum (Hjorth 1961).
- Foeniculum vulgare
The young blanched leaves provide a vegetable and the fruit a condiment. Fennel tea infusions applied to inflamed skin increased the inflammation. Oil of fennel is reported to produce dermatitis in sensitive individuals (Greenberg and Lester 1954). Cross-sensitivity with Oil of Anise (Pimpinella) was reported by Loveman (1938). The plant has been implicated in causing phytophotodermatitis (Pathak et al. 1962). Ingestion of fennel and fennel seed were implicated in a case of bronchial asthma (Levy 1948).