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- Gluta L.
- Rengas, Renghas, Ringas, Rungus
A recent study of the genera Gluta and Melanorrhoea Wall. by Hou (1978) has resulted in the proposal that the whole of the genus Melanorrhoea be reduced to Gluta. The new enlarged genus thus contains about 30 species distributed in Madagascar, India, Burma, Thailand, Indochina, China, and throughout Malesia but not (yet) in the Philippines (Hou 1978).
Various vernacular names — rengas (Malaya), hangus (Penang), rangus (Sakar), ruengas (Sudan), ingas (Indonesia), angas and ligas (Philippines) — are applied to trees the sap of which produces sores of the skin. The species concerned are mainly in the genus Gluta; their white irritant sap turns black on exposure to the air (Burkill 1935), a feature commonly found in the Anacardiaceae (Hou 1978). In Malaya, the more poisonous kinds are usually called kerbau jalung — the untamed buffalo — as are some species of Melanochyla Hook.f. It is unwise even to sit beneath these, for raindrops carry down the poison from the leaves (Corner 1952).
Many provide hard, durable, beautifully marked timber, the heartwood often being blood-red in colour. However, the irritancy of the sap limits its value. In the timber trade, the term rengas or renghas is reserved for the red heartwood of Gluta species. The terms Singapore mahogany and Straits mahogany may also refer to timber from Gluta species. Only a few species are regularly distributed by the timber trade (Hausen 1973). It is excellent material for furniture and turning, and is used in Malaya for making "daching" — Chinese weighing scales. However, even thoroughly seasoned timber, furniture, etc. may affect allergically sensitised persons. The black sap tends to find its way through polish, but a further application of polish, particularly a modern polyurethane lacquer, after two or three years is likely to alleviate the problem (Burgess 1966).
Rengas poisoning in the form of acute dermatitis with constitutional symptoms is not uncommon in Malaya in estate labourers, gardeners, and wood cutters (Gimlette 1929, Samuel 1935). Contact not only with the fresh sap, but also with branches that have been cut and dried for months can produce the sores (Hornsey 1914). Corner (1952) noted that Gluta species have been inadequately collected because the irritant sap deters plant collectors seeking material for herbaria. In the last century, Upwich (1894) described dermatitis that occurred in two companies of soldiers after they waded in a river on the banks of which were growing rengas trees whose fruits had contaminated the river. Noosten & Visser (1936) also noted that the fruit juice can cause dermatitis.
- Gluta aptera Ding Hou
- (syns Melanorrhoea aptera King, Melanorrhoea inappendiculata King)
- Gluta beccarii Ding Hou
- (syn. Melanorrhoea beccarii Engl.)
According to Burgess (1966), both species have irritant sap, but Halim et al. (1980) could not detect urushiols in an extract of the bark of Melanorrhoea beccarii.
- Gluta curtisii Ding Hou
- (syn. Melanorrhoea curtisii Oliver)
- Curtis' Rengas
The sap causes dermatitis (Brown 1891, Matthes & Schreiber 1914, Senear 1933, Corner 1952). A scantily clad person who scrambles through the broken branches may suffer a widespread dermatitis, which may be complicated by fever and other constitutional symptoms, and has occasionally proved fatal (Burkill 1935).
- Gluta elegans Hook.f.
- Penang Rengas
The sap causes dermatitis (Burkill 1935, Corner 1952).
- Gluta laccifera Ding Hou
- (syn. Melanorrhoea laccifera Pierre)
The milky juice is caustic (Perry & Metzger 1980). Bertrand & Brooks (1934) isolated from this species a phenolic compound which they named moréacol. Although the structure of this compound has not been confirmed, Backer & Haack (1941a) believed moréacol to be identical with thitsiol, an urushiol from Gluta usitata Ding Hou.
This species is a source of a lacquer, named camboge lacquer, in Indochina (see also G. usitata).
- Gluta malayana Ding Hou
- (syns Melanorrhoea malayana Corner, Melanorrhoea pilosa Ridley)
- Malayan Rengas, Kerbau Jalang, Rengas
This species has been reported to be irritant (Corner 1952).
- Gluta renghas L.
- (syns Gluta benghas L., Stagmaria verniciflua Jack)
- East Coast Rengas, Ape-Nut, Rengas, Jintun
The timber of this large river-side tree is beautifully marked, but has a sinister reputation amongst forestry workers (Foxworthy 1927, Lewin 1928, Grevenstuk 1937). However, it is used for building, for boats, for furniture, and for inlay work (Hausen 1973).
Gimlette (1929) described the sap as irritant. Those employed in felling the trees may develop an acute vesicular dermatitis (Ridley 1922). A chair made from the wood of this species has caused dermatitis of the legs (Hausen 1973).
The poisonous character of G. renghas was known to Rumphius (Herb. Amboin. ii. 259, t. 86; 1750): "The exhalations of this tree are considered noxious, and the people of Macassar and other parts of Celebes in particular, entertain such dread of it, that they dare not remain long under it, much less repose beneath its shade; they say that whoever receives the droppings from it will have his body swell and be affected with malignant sores".
"Not only are the fruit, leaves, and twigs of the Rengas trees (species of Gluta and Melanorrhoea) poisonous, but the timber also, even after long keeping, is apt to produce injury. Dr. Brown says that he was informed that after years of seasoning, when the wood is cut up, it gives rise to painful and intractable eruptions on the hands and bodies of the workmen. The timber is a very handsome red wood, streaked more or less with black, and was formerly known as Singapore Mahogany and much valued as a cabinet wood or for buildings. The Kedah Malays, on felling a tree, would leave it lying in the forest till the bark and sap-wood was rotted away or removed by termites, after which they said it was safe to move. As a furniture wood, however, it went out of fashion, as even after being made up it was said to seriously affect many persons living in the room with it, producing great irritation of the mouth, nose and throat, especially when it began to get old, worn-out and dusty" (Ridley 1911, cited by Sprague 1921).
The vesicant latex of this species has been found to contain an incompletely characterised 3-heptadecenylcatechol, which was named glutarenghol (Backer & Haack 1941a).
- Gluta speciosa Ding Hou
- (syn. Melanorrhoea speciosa Ridley)
Burgess (1966) reports that this species is irritant.
- Gluta tavoyana Hook.f.
- Gluta tourtour Marchand
The sap of both of these species is irritant (Thiébault 1965).
- Gluta usitata Ding Hou
- (syn. Melanorrhoea usitata Wall.)
- Theetsee, Burmese Lacquer Tree
This species is the source of lacquer in Burma. The tree is tapped by making V-shaped cuts with a chisel. The bark above each cut is torn to produce a cavity into which is inserted a shoot of bamboo with an obliquely cut mouth, to form a spout. The latex, which at first is yellow-white, turns black but remains fluid. It is stored in jars for distribution. It can be used as a varnish or, after mixing with ashes, sawdust, or similar material, it can be moulded. For ornamental use, it may be coloured by the addition of pigment. The varnish is used on umbrellas, to give a surface to trays, on drinking cups and similar articles, and as a cement for Burmese glass ceramics (Watt 1906, Burkill 1935).
The timber from this species is known in the trade as varnish tree or mai leek. It is hard, durable, and finely marked; it is used for furniture, inlay work, and the like (Hausen 1973).
The sap may splash the skin whilst the trees are being felled, producing much irritation, hence wood cutters object to fell the tree (Watt 1906). The sawdust of trees felled three or four years earlier, and even old furniture, may cause dermatitis and irritation of the mouth nose and throat (Watt 1891, Schwartz et al. 1957, Behl et al. 1966).
According to Nadkarni (1976), the oleoresin of this species is used in Burma in combination with honey as an anthelmintic in skin diseases. If it be too much handled it causes erysipelas-like swellings among some, which are cured by applying an infusion of teak wood.
An incompletely identified 4-heptadec(en)ylcatechol, which was named thitsiol, has been reported to occur in this species (Majima 1922b).
- Gluta velutina Blume
- (syn. Gluta coarctata Hook.f.)
- Singapore Mahogany, Water Rengas, Rengas Ayer
The wood causes dermatitis; the fruit and leaves are also poisonous and have been used for criminal purposes (Ridley 1911, 1922, Corner 1952). The dried wood and sap both retain their dermatitic properties (Burkill 1935).
- Gluta virosa Ridley
- Wild Buffalo Tree
This species can produce dermatitis (Gimlette 1929).
- Gluta wallichii Ding Hou
- (syns Melanorrhoea wallichii Hook.f., Melanorrhoea maingayi Hook.f., Melanorrhoea woodsiana Scorotech.)
- Wallich's Rengas
The beautifully coloured wood is used in furniture, and is one of the timbers known in the trade as rengas. It has so far been imported to Europe only as samples (Hausen 1973). Felled trees are commonly left in the jungle for the sapwood to be destroyed by decay and by white ants (termites), after which they are considered safe to move.
The sap causes dermatitis (Ridley 1911, 1922, Matthes & Schreiber 1914, Lewin 1928, Senear 1933, Corner 1952, Schwartz et al. 1957, Thiébault 1965, Burgess 1966, Behl et al. 1966).
- Gluta wrayi King
- Straits Mahogany
This species is said to be the most virulent of the rengas (Ridley 1911, 1922, Burkill 1935). The timber is beautifully marked.
- Heeria argentea Meisn.
- (syns Anaphrenium argenteum E.Mey., Roemeria argentea Thunb., Rhus thunbergii Hook.)
- Rockwood, Rock Ash, Wild Apricot
The genus Heeria Meisn. is monotypic, forming an evergreen tree that is found growing naturally in the southwestern Cape region of South Africa. According to Von Teichman & Van Wyk (1996), the gum exudate from the bark has been used as an ointment to draw boils and abscesses.
This species has been reported by Ross (1959) to have caused severe dermatitis in Pondoland. However, the Curator of the Pretoria Botanical Gardens has not seen reactions to the plant in visitors who had handled it.
- Holigarna arnottiana Hook.f.
This species contains a black, very acrid oleoresin, the powerfully vesicant properties of which are dreaded by local people (Behl et al. 1966). Not all persons coming into contact with the sap develop dermatitis (Chopra et al. 1949), suggesting allergenicity rather than irritancy.
The fixed oil of the seed kernel has been found to contain laccol, identified as 3-n-heptadecadienylcatechol (Nair et al. 1952a).
- Holigarna grahamii Hook.f.
- Holigarna longifolia Buch.-Ham.
These species have properties similar to those of H. arnottiana. The black varnish obtained from H. longifolia is caustic and vesicant (Chopra et al. 1949).
- Holigarna helferi Hook.f.
The tree has so evil a reputation (because of its irritant sap) that it can hardly be felled (Watt 1906).
- Lannea A.Rich.
About 70 species are native to tropical Africa, and one to Indomalaysia. Some of the African species yield timber that is used locally; others are employed for a variety of purposes in indigenous medicine (Watt & Breyer-Brandwijk 1962).
- Lannea grandis Engl.
- (syn. Odina wodier Roxb.)
- Wodier Tree, Kayu Kuda, Kedondong
This East Indian member of the genus is strongly irritant (Verbunt 1933).
- Lithraea brasiliensis Marchand
The timber, known in the trade as aroeira or pao bugre, is used for posts and fences, and sometimes for furniture. The sap is powerfully irritant (Mors & Rizzini 1961) and severe dermatitis has resulted from contact with the timber (Hausen 1981).
- Lithraea caustica Hook. & Arn.
- (syn. Lithraea venenosa Miers)
The timber, known in the trade as aroeira (see also L. brasiliensis above) or litre, is used in Brazil and Chile for cabinet work. Severe dermatitis has resulted from contact with the wood (Hausen 1970, 1981), although according to Webster (1911) the dried wood is said to be harmless. Cross-sensitivity to Rhus L. (Toxicodendron Mill.), Mauria Kunth, and other members of the Anacardiaceae was investigated by Oliveira Lima (1953) and Hurtado (1968).
Barham (1794) referred to swelling of the face and body from sleeping under the tree. The sap and, at certain times of the year, the exudate from the leaves is highly irritant (Sprague 1921): Feuillée, who visited South America in 1702–12, related that some of the seamen of his ship suffered severely as the result of cutting down some "Llithi" trees (Lithraea caustica) on the coast of Chile. By the following day, their heads had swollen to an extraordinary size, and their features had become indistinguishable; they might have been taken for monsters rather than men (Obs. ii. 33, t.25, fig. dextra; 1725). According to Molina (Hist., Engl. ed. 144; 1809), "the effluvium from this tree, especially in summer, produces painful pustules and swellings on the hands and faces of those who stop beneath its shade. This effect is various, however, with various persons: there are some who are very little, if at all, incommoded by it, while others, who merely pass by the tree, are severely affected; though never attended with fatal consequences, it is, nevertheless, very troublesome. Great precaution is requisite in cutting the tree, as its viscous juice is extremely caustic; but when dry, the wood loses all its injurious qualities". Molina, who has been described as "one of the most pernicious blunderers who have brought confusion into Natural History" (J. Ball, Notes Nat. S. Am. 175; 1887) is not very trustworthy; but, according to Gillies, "the statement made by Molina, relative to the poisonous nature of this tree, seems to be well founded; as I am informed, by several intelligent people, that individuals resting or sleeping under it at certain times of the year, are afterwards attacked with eruptions all over the body" (Hook. & Arn. Bot. Beechey's Voy. 16; 1832). Gay (Fl. Chil. ii. 44; 1846) stated that the "Liti" or "Litre" tree (Lithraea caustica) is common on hills and sun-exposed plains in central Chile, extending from Coquimbo to Arauco; and that the danger of remaining underneath it or of burning it is well known. It is mostly women, children, and persons of weak constitution who are affected.
- Lithraea molleoides Engl.
- (syn. Lithraea aroeirinha Marchand)
The oleoresin from this species has been used to induce allergic contact dermatitis in guinea pigs (Oliveira Lima 1953).
- Loxopterygium huasango Spruce
- Hualtaco Tree
Contact with the leaves can cause dermatitis but the wood does not seem to be irritant (Paulson 1942).
- Loxopterygium lorentzii Griseb.
- (syns Schinopsis lorentzii Engl., Quebrachia lorentzii Griseb.)
- Red Quebracho
This tree yields a timber that is useful for building and constructional work (Hausen 1970). It has been listed as irritant by Schwartz et al. (1957) and Orsler (1973).
Contact with branches, leaves or sawdust may provoke dermatitis in sensitive persons (Di Lullo 1928) and the condition is sufficiently common to have acquired the vernacular name of "mal de quebracho". The diagnosis may be confirmed by patch testing with an alcoholic extract or with an aqueous distillate (Di Lullo 1934). The dermatitic agent in this species appears not to have been identified, but Di Lullo (1934) suggests that a substance similar to cardol (see Anacardium occidentale) is responsible. He showed that sensitisation was involved since only a proportion of those exposed developed dermatitis, and this only after a latent period.