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- Rhus L.
There are over 200 species widely distributed over subtropical and warm temperate regions.
Many species formerly considered to belong to the genus Rhus are now placed in the genus Toxicodendron Mill. (see Gillis 1971). Toxicodendron now includes most of the more virulently dermatitic species such as poison ivy and poison oak, even though the reclassification was carried out on morphological rather than chemical grounds.
According to Chopra et al. (1949), many Rhus species cause dermatitis. Some Indian villagers have an almost superstitious dread of all species; they believe that the smoke from the burning wood can cause swelling and vesication of the skin. (Since the genus Toxicodendron occurs in eastern Asia as well as in North America, it is likely that some of the Rhus species referred to by Chopra et al. were actually Toxicodendron species).
Species of Rhus are commonly referred to as sumachs or sumacs. Sumac dermatitis in Russia was reviewed by Gorbovitski et al. (1974).
- Rhus chinensis Mill.
- (syns Rhus japonica Buch.-Ham ex D.Don, Rhus javanica L. var chinensis T.Yamaz., Rhus semialata Murray, Toxicodendron semialatum Kuntze)
- Chinese Sumach, Nutgall Tree, Gallensumach
This plant, a native of China and Japan, provides Chinese (or Japanese) nutgalls – also known as Wu Pei Tzu, Wu Bei Zi, or Galla Sinensis (五倍子) – which grow on the leaves and leaf stalks in response to the activities of certain insects (Chinese sumac aphids: Schlechtendalia chinensis Bell, fam. Aphididae). These galls are rich in tannins. In Chinese traditional medicine, they are used in topical applications to chancres, swellings and wounds (Stuart 1911).
The residue obtained in the factory production of tannin from an ethereal extract of "Galläpfeln" was found to contain a substance named cyclogallipharic acid (Kunz-Krause 1904). The title of Schelle's dissertation from Basel University in 1903, in which the work was originally described, later to be formally published in 1904, was entitled: "Beitrage zur Kenntnis der chemischen Bestandteile der Eichengallen. Ueber die Cyklogallipharsäure, eine neue, in den Galläpfeln vorkommende, cyklische Fettsäure" (see Kunz-Krause & Schelle 1904). This appears to refer to galls obtained from oak species ("Eichengallen"), otherwise known as Aleppo galls (found on Quercus infectoria G.Olivier fam. Fagaceae – see Trease & Evans 1966). It is likely that Schelle's work was actually – perhaps unwittingly – carried out on Chinese galls ("chinesischen Galläpfeln") found on Rhus chinensis. Indeed, Kawamura (1928) referred to "japanischen Galläpfeln" as the botanical source of the cyclogallipharic acid that Kunz-Krause & Schelle had isolated. He also reported that cyclogallipharic acid, upon decarboxylation, produced cyclogallipharol, an alkylphenol that was identical with hydroginkgol derived from Ginkgo biloba L. (fam. Ginkgoaceae). And he established that hydroginkgol was, structurally, 3-pentadecylphenol (see also Loev & Dawson 1958). It follows that cyclogallipharic acid, although only incompletely characterised by Kunz-Krause & Schelle (1904) is, structurally, 6-pentadecylsalicylic acid, a member of a class of alk(en)yl salicylic acids known collectively as anacardic acids. Bagchi et al. (1985) subsequently reported the isolation and characterisation of 6-pentadecylsalicylic acid from a petrol extract of the leaves of Rhus semialata.
Whilst 6-pentadecenylsalicylic acid has been shown to be a sensitiser in guinea pigs (Lepoittevin et al. 1989, Hausen 1998), the saturated side-chain analogue 6-pentadecylsalicylic acid showed no activity as an elicitor on guinea pigs sensitised to unsaturated side-chain analogues of anacardic acid from Ginkgo biloba L. (fam. Ginkgoaceae).
- Rhus chinensis Mill. var roxburghii Rehder
- (syns Rhus roxburghii Decaisne ex Steud., Rhus semialata Murray var roxburghii DC., Rhus sinensis Murray var roxburghii Rehder)
- Chinese Sumac
Kuo et al. (1991) reported the isolation and characterisation of 6-pentadecylsalicylic acid from a n-hexane extract of the stems of Rhus semialata var roxburghii.
Whilst 6-pentadecenylsalicylic acid (a member of a class of alk(en)yl salicylic acids known collectively as anacardic acids) has been shown to be a sensitiser in guinea pigs (Lepoittevin et al. 1989, Hausen 1998), the saturated side-chain analogue 6-pentadecylsalicylic acid showed no activity as an elicitor on guinea pigs sensitised to unsaturated side-chain analogues of anacardic acid from Ginkgo biloba L. (fam. Ginkgoaceae).
- Rhus coriaria L.
- Sicilian Sumach
According to Anon (1908), and repeated by (Maiden 1909), Rhus coriaria "… is unquestionably dangerous and produces an erysipelas-like affection of the skin of persons who gather the leaves for the sake of the tannin they contain." The species is found in the Mediterranean region and Asia Minor. Its young branches are used in the tanning of Moroccan leather (Polunin 1969).
- Rhus glabra L.
- Smooth Sumach
This eastern North American species is said to cause dermatitis (Pardo-Castello 1923).
- Rhus insignis Hook.f.
The leaves, fruit, and bark of this species, which grows in Assam, can produce dermatitis; the sap is vesicant (Behl et al. 1966). The smoke from the burning wood has been reported to cause dermatitis (Watt & Breyer-Brandwijk 1962).
- Rhus perrieri H.Perrier
- (syn. Protorhus perrieri Courchet)
The resin is used as a depilatory by girls among the Mikea hunter-gatherers of Madagascar (Stiles 1998).
- Rhus punjabensis J.Stewart
The leaves, bark, fruit, and sap can produce dermatitis (Behl et al. 1966). The plant is found in central and western China, and in the Himalayas.
- Rhus pyroides Burchell
A scratch or prick from the sharp point of a twig (the plant has no thorns) is extremely painful and burns like fire, hence the specific epithet (Watt & Breyer-Brandwijk 1962).
- Rhus simarubaefolia A.Gray
- (syn. Rhus taitensis Guill.)
The wood of this species, which is found in the South Pacific, is used to make canoes in Samoa (Usher 1974). This native plant of Guam can produce dermatitis (Souder 1963).
- Rhus typhina L.
- (syn. Rhus hirta Sudw.)
- Stag's Horn Sumach, Antler Tree, Lemonade Tree
This ornamental tree is a native of North America but is widely cultivated elsewhere. Its yellow wood is soft and light, and is used for inlays (Hausen 1970).
It is recorded as causing dermatitis (Großmann 1910). The leaves are said to contain irritating sap (Lindemark 1971). However, patch tests with the leaves produced no reactions on 50 consecutive eczema patients in Denmark, but did produce a strongly positive reaction in one of ten subjects in the US known to be sensitive to poison oak (Toxicodendron diversilobum Greene) (Maibach & Hjorth 1973). Ross (1974) observed a case of contact dermatitis from R. typhina in Newfoundland.
- Rhus wallichii Hook.f.
- Red Lac Sumach, Akoria, Arkol, Kambul
The wood of this Himalayan species is used for tool handles and musical instruments. The wax from the fruit is used to make candles, and a varnish is extracted from the trunk (Usher 1974).
According to Behl et al. (1966), this small tree is very closely allied to the Japanese lacquer tree (Toxicodendron vernicifluum F.A.Barkley, syn. Rhus verniciflua Stokes) and possesses similar properties. Nadkarni (1976) records that the juice of the leaves is corrosive.
- Schinopsis Engl.
- (syn. Quebrachia Griseb.)
The seven species in this genus are confined to South America. The timber of Schinopsis balansae Engl., known as quebracho, may be found in commerce (Hausen 1981).
- Schinopsis quebracho-colorado F.A.Barkley & T.Mey.
- (syn. Aspidosperma quebracho-colorado Schldl.)
This species has been implicated as a cause of phytophotodermatitis (Pathak 1974).
- Schinus L.
The 30 species are native to northern and central South America, Central America, and Mexico. Some are cultivated as ornamental or shade trees wherever the climate is suitable.
The aroeira sickness was described by von Bassewitz (1928). This author established that up to 10% of the population of southern Brazil has some degree of hypersensitivity to the aroeira tree. Those who were sensitive reacted not only to the tree itself, but also to dry, seasoned wood such as furniture that has been in use for some time. Unfortunately, the botanical identity of the aroeira has not been established. Von Bassewitz (1928) and Freise (1932) thought that aroeira was a species of Schinus. The timber from S. molle L. is known as aroeira, and a synonym of S. terebinthifolius Raddi is S. aroeira Vell. The term aroeira is also used for the timber from Astronium Jacq. and Lithraea Miers species. Hausen (1981) notes that the timber of both Lithraea brasiliensis Marchand and Lithraea caustica Hook. & Arn. is called aroeira. Aroeira may also refer to Lithraea aroeirinha Marchand. It is probable that the term aroeira as used in South America for species of Astronium, Lithraea, and Schinus is used as loosely as is the term rengas in Malaya for species of Gluta, Melanochyla, Parishia, and Semecarpus.
- Schinus molle L.
- Peruvian Pepper Tree, Peruvian Mastic Tree, Californian Pepper Tree
Aroeira, the durable timber of this species and probably of related species, is used for bridge construction and fencing (Hausen 1973). The resin of the tree is a source of American mastic.
Watt & Breyer-Brandwijk (1962) note that the leaf and bark have been used as a local application to wounds and sores.
If ingested, the fruit can cause gastro-intestinal inflammation and haemorrhoids (Ruiz 1940), but has been used as a substitute for black pepper (Piper nigrum L., fam. Piperaceae) in Latin America, and northern and southern Africa (Morton 1976).
A fragrance raw material known as schinus molle oil is the essential oil prepared by steam distillation of the green or ripe fruits of this species. Its principal constituents are pinene, phellandrene, and carvacrol. When applied undiluted to the skin of mice and swine, it was found to be non-irritant. However, when applied to rabbit skin under occlusion for 24 hours, it was found to be moderately irritant. The undiluted oil showed no phototoxicity to mice nor swine, and when applied at a concentration of 4% in petrolatum to the skin of 25 human volunteers, no sensitisation could be induced (Opdyke 1976).
Dermatitis resembling poison ivy (Toxicodendron Mill. sp.) dermatitis occurs in those who become sensitised to the tree, its timber, or its sawdust. According to Hausen (1970), the dermatitis is likely to be caused by a phenolic substance, but no clinical investigations have been published.
- Schinus terebinthifolius Raddi
- (syn. Schinus aroeira Vell.)
- Brazilian Pepper, Florida Holly, Christmas Berry, False Pepper
Aplin (1966) noted that this species can produce skin ailments. Dermatitis as well as eye-inflammation and facial swelling are common complaints of those who trim the tree when it is in bloom or those who repeatedly trim a non-blooming hedge of this species. Crushed berries from sprays used for indoor decoration have caused severe respiratory irritation. […] children who play beneath the tree or climb it [may] suddenly exhibit symptoms usually associated with head colds or the early stages of "flu." (Morton 1969). Direct contact with the exudate from the trunk causes vesication and severe itching, the lesions resembling second-degree burns. It is also recorded that the resinous exhalation from the tree causes skin eruptions resembling those of measles or scarlet fever. This may be observed in persons resting under the tree, and in persons engaged in felling, trimming, or pruning the branches, especially while the plant is in bloom (Morton 1978a).
- Schinus velutinus I.M.Johnst.
- (syns Duvaua velutina Turcz., Schinus latifolius Engl.)
According to an herbarium note found by von Reis Altschul (1973), the foliage causes skin irritation.