Melaleuca cajuputi (PROSEA)
Melaleuca cajuputi Powell
- Protologue: Pharm. Lond. Transl.: 22 (1809).
- Family: Myrtaceae
- Chromosome number: 2n= 22
- Myrtus saligna Burm.f. (1768),
- Melaleuca minor Smith (1812),
- M. leucadendron (L.) L. var. minor (Smith) Duthie (1878).
- Cajeput (also spelt "cajaput" or "cajuput"), swamp tea-tree (En). Punk tree (Am)
- Indonesia: kayu putih (general), galam (Sundanese), gelam (Javanese, Madurese)
- Malaysia: kayu putih, gelam
- Cambodia: smach chanlos
- Thailand: samet-khao
- Vietnam: cây tràm.
Origin and geographic distribution
The exact limits of the natural range of M. cajuputi are not known, as it has been cultivated in Asia for several centuries. The approximate boundaries cover a latitudinal range from 18°S to 12°N from tropical, northern Australia (Queensland, Northern Territory, Western Australia) through south-western Papua New Guinea, Indonesia, Malaysia to Thailand and Vietnam.
Natural populations of M. cajuputi in eastern Indonesia occur on the Moluccan Islands of Buru, Seram and Ambon. M. cajuputi has been planted since 1926 in central Java for oil production, using seed from Buru. It is also planted in Malaysia.
The leaves of M. cajuputi possess antibacterial, anti-inflammatory and anodyne properties and are used traditionally against pain, burns, colds, influenza and dyspepsia. Cajeput oil is produced from the leaves by steam distillation. The oil is a common household medicine, especially in South-East Asia, used internally for the treatment of coughs and colds, against stomach cramps, colic and asthma. It is used externally for the relief of neuralgia and rheumatism, often in the form of ointments and liniments, and for the relief of toothache and earache. It is also applied in treating indolent tumours. The oil is reputed to have insect-repellent properties; it is a sedative and relaxant and is useful in treating worms, particularly roundworm, and infections of the genito-urinary system. It is used as a flavouring in cooking and as a fragrance and freshening agent in soaps, cosmetics, detergents and perfumes.
The wood of M. cajuputi is hard and fairly heavy and makes good fuelwood. Of limited interest for sawmilling, it is generally used in the round or roughly fashioned and is suitable for posts, poles and piles. The timber tends to check and warp, but when carefully seasoned it is suitable for general construction and flooring. The soft bark is used as a packing material, in boat building, filling mattresses or pillows and for insulation. M. cajuputi is an important honey tree and often plays an important role in estuarine environments where it provides habitat for birds, fish and shrimps. It makes an excellent shade and shelter tree and is one of the few trees that can be grown successfully to reforest exposed locations on brackish soils and acid sulphate soils.
Production and international trade
The two principal centres of production of cajeput oil are Indonesia and Vietnam. In Indonesia, commercial oils are produced both from natural stands in the Moluccas and from plantations in Java. Estimates of production from the natural stands (about 200 000 ha) suggest that a total of some 90 t of oil are produced annually on Buru, Seram, Ambon and adjacent islands. Production from an estimated 9000 ha of government-owned plantations in Java amounted to approximately 280 t in 1993. Production in southern Vietnam is estimated to be in the order of 100 t per year, from about 120 000 ha natural Melaleuca forest. Smaller amounts of oil are also exported from Malaysia.
Annual world production of cajeput oil is very difficult to quantify accurately, but appears to be in excess of 600 t. In 1985 it was valued at US$ 500 000. With a 1997 distillery-gate price in Indonesia of about US$ 9.4 per kg of oil of 55% cineole, the value of the industry may now exceed US$ 5.6 million before further processing.
The oil is often exported as crude oil, mainly to Europe. There is no internationally accepted quality standard for cajeput oil. As a result, there may be major differences between batches. Cajeput oil is purchased and sold by traders in three grades in the Moluccas. Grading depends on where the trees are grown, which appears to affect the proportion of 1,8-cineole in the oil. Grade 1 oil of 55-65% cineole content comes from hillside trees and fetched US$ 8.8-9.6 per kg at the farm gate in 1995. Grade 2 oil of 20-55% cineole content comes from trees on lower sites and is priced at about US$ 7.2 per kg. Grade 3 oil presumably comes from locations that produce oils of very low cineole content, such as Gogoria and Wai Geren on Buru Island.
There is wide variation in the chemical composition of cajeput oil. It appears that different chemical forms predominate in different parts of the natural range of M. cajuputi and that their occurrence partly parallels the morphological variation in the species. Commercial cajeput oil is derived mostly from the cineole-rich form, M. cajuputi subsp. cajuputi. The other subspecies produce oils of generally low cineole content.
The oil of M. cajuputi subsp. cajuputi usually contains substantial amounts of 1,8-cineole (3-60%), and the sesquiterpene alcohols globulol, viridiflorol and spathulenol. Other compounds present, usually in quantifiable amounts, are limonene,β-caryophyllene,α-humulene, viridiflorene,α-terpineol,α- andβ-selinene and caryophyllene oxide. The oil yield of fresh leaves ranges from 0.4-1.2%. Cajeput oil is mainly a pale yellow mobile liquid sometimes with a greenish-blueish tint. The green-blue coloration may be a function of the presence of azulene compounds in the fractions of the oil that have a higher boiling point, but has also been attributed to chlorophyll or small amounts of copper in the oil. The green colour mostly disappears in storage. Some cajeput oils with significant amounts of eudesmol isomers solidify into a whitish paste after extraction. The odour of commercial oils is rather penetrating, with a camphoraceous-medicinal aroma, similar to cineole-rich eucalypt oil but milder and more fruity. The almost fruity-sweet body notes and the soft tones in the dry-out are very characteristic. The taste is aromatic; the initial burning sensation on the tongue is followed by a cooling sensation. Cajeput oil is classified as non-toxic (rodent LD50of 2-5 g/kg) and non-sensitizing, although skin irritation may occur at high concentrations. It has been approved for food use by the Food and Drug Administration (FDA) of the United States. See also: Composition of essential-oil samples.
The wood of M. cajuputi has a yellowish sapwood, merging gradually into pinkish-grey heartwood. It has a high silica content (0.2-0.95%) which blunts saws. Generally used in the round or roughly fashioned, cajeput timber is durable in ground or water. It is hard and heavy, with a green density of about 1070 kg/m3and an air-dry density of about 750 kg/m3. Careful drying is necessary to minimize checking and warping. Collapse is slight, shrinkage about 3.5% radially and 7% tangentially. It is difficult to plane and mortise due to interlocking grain, but glues well and is a good jointing timber.
On average there are 2 700 000 viable seeds per kg.
Adulterations and substitutes
The large variation found in the chemical composition of commercial cajeput oil is partly a reflection of the substantial natural variation in M. cajuputi, but is also due to the admixture of similar oils from other species; adulteration with synthetic compounds is also common. Cajeput oil is sometimes adulterated with kerosene or fatty oils, its odour being so strong that moderate addition of kerosene is hardly noticeable. Foam formation on violent shaking indicates such adulteration. Substitute oils often marketed as cajeput oil come from the liniment tree (Asteromyrtus symphyocarpa (F. Muell.) L.A. Craven (synonym Melaleuca symphyocarpa F. Muell.)) and the broad-leaved paperbark (Melaleuca quinquenervia). In western markets cajeput oil is often replaced by the less expensive eucalypt oil.
- Evergreen shrub or usually single-stemmed tree up to 25(-40) m tall with an extensive root system, sometimes with aerial adventitious roots. Bark layered, fibrous and papery, grey to white. Crown fairly dense and wide, somewhat silvery in appearance; smaller branches and twigs slender but not drooping, young shoots densely silky hairy with spreading fine hairs up to 2 mm long.
- Leaves alternate, flat, silky hairy to glabrescent; petiole compressed to concave-convex, 3-7(-11) mm × 1.1-2.3 mm, straight or curved; blade elliptical to lanceolate-elliptical, sometimes obliquely so, 5-10(-12) cm × 1-2.5(-6) cm, 2-10 times longer than wide, attenuated or sometimes abruptly rounded at base, apex acute or narrowly obtuse, often apiculate, thinly coriaceous, dull green, finely but obscurely dotted with oil glands, with 5-7 prominent veins and prominent reticulation.
- Inflorescence a terminal or upper-axillary spike, single or 2-3 together; spike fairly densely flowered, 3.5-9 cm × 2-2.5 cm; rachis 1-1.3 mm thick, enlarging at anthesis, densely pilose; bracts ovate, striate, villous, caducous; bracteoles absent.
- Flowers in triads, white, greenish-white or creamy; calyx tubular, 2.5-3 mm long, pubescent, tube subcylindrical, 1.2-1.9 mm × 1.5-2 mm, at base adnate to ovary (persistent in fruit), with 4 triangular to semicircular lobes 0.7-0.9 mm × 1.2-2 mm with thin margin; petals 5, broadly obovate-spatulate with a short claw, 2-2.7 mm × 1.8-2.3 mm, blade suborbicular with 7 slender branched veins and streaked with glands; stamens numerous, 7-10 mm long, white, glabrous, arranged in bundles with a claw 1-3.5 mm long; per bundle 7-10 filaments, attached to the upper margin of the claw, free part up to 8 mm long; anthers 0.4-0.55 mm long; pistil with 3-celled ovary about 1 mm long, style 6-9 mm long and a small stigma.
- Fruit a cup-shaped to globose, many-seeded capsule, 3-3.5 mm × 3.5-4 mm, orifice 1.5-2 mm in diameter with thin valves.
- Seed linear, minute.
Growth and development
M. cajuputi is a long-lived, moderately fast-growing tropical tree adapted to both waterlogged and well drained soils. On soils subject to prolonged waterlogging it develops aerial adventitious roots, which can form buttresses on the lower trunk. Like all melaleucas, it does not develop dormant buds and grows whenever conditions are favourable. After bush fires, it will regenerate by seed, coppicing and from root suckers. Young trees may grow 2.3 m in height and 7 cm in diameter per year and set their first flower buds when only 13-14 months old. Melaleucas appear to be obligate outcrossers and pollination is mainly by insects, but also by birds and small mammals. In Java M. cajuputi flowers throughout the year; in Australia it flowers from March-June and from August-December. Mature seeds have been collected in Australia in October-November. The very small seeds are orthodox and germinate readily in moist, warm conditions with no pretreatment.
Other botanical information
M. cajuputi is one of the 10 species that together form the M. leucadendra (L.) L. (also often named M. leucadendron) complex. Many early references to M. leucadendra or M. leucadendron yielding cajeput oil from Indonesia and Vietnam in fact refer to M. cajuputi. It is often difficult to distinguish species within the complex, especially in areas where they overlap, because distinctive characteristics also overlap. Within the complex, M. cajuputi is most closely related to M. viridiflora Sol. ex Gaertner and M. quinquenervia (Cav.) S.T. Blake. Distinctive characteristics are: M. cajuputi has leaves with petiole 3-11 mm long, blade mostly longer than 5 cm and less than 2.5 cm wide, old leaves densely dotted with glands, rather thin in texture, with reticulations almost as prominent as the main veins and young shoots with spreading hairs. M. viridiflora has leaves with petioles 1-2 cm long, blades wider than 2.5 cm, very thick, young shoots with appressed silky hairs. M. quinquenervia is like M. cajuputi but its old leaves are not conspicuously dotted with glands, not thin-textured and have obscure reticulations.
Differences in genetic structure between populations east and west of Wallace's line based on allozyme variation led to the hypothesis that M. cajuputi has spread naturally from Australia into South-East Asia, aided by its propensity for invading disturbed sites. M. cajuputi is the only species out of about 250 in Melaleuca L. to occur naturally west of Wallace's Line. M. cajuputi is rather variable and based on differences in morphology, chemical content and geographic distribution 3 subspecies are distinguished:
- subsp. cajuputi. Leaf width (6-)10-16(-26) mm; leaf length/width ratio 2.8-9.7; stamens per budle (6-)8-11(-14); stamen bundle claw length 1-1.6 mm. Distribution: Indonesia (Buru, Ceram, Tanimbar Islands, Timor) and Australia (Western Australia, Northern Territory). This is the main source of cajuput oil and is often cultivated. Purely cultivated forms could better be classified as cultivars.
- subsp. cumingiana (Turcz.) Barlow. Leaf width (15-)19-28(-39) mm; leaf length/width ratio 2.2-2.9; stamens per bundle (4-)6-8(-10); stamen bundle claw length 2.1-3 mm. Distribution: Burma (Myanmar), Thailand, Vietnam, Peninsular Malaysia, Indonesia (Sumatra, western Java, south-western Kalimantan). Within the natural range of this subspecies, cultivars of subsp. cajuputi occur in plantations sometimes with characteristics intermediate between the 2 subspecies.
- subsp. platyphylla Barlow. Leaf width (17-)25-50(-60) mm; leaf length/width ratio 1.3-6.5; stamens per bundle (8-)9-12(-15); stamen bundle claw length 1.1-3.5 mm. Distribution: Indonesia (southern Irian Jaya), Papua New Guinea (southern) and Australia (Queensland).
M. cajuputi is primarily found in coastal areas of the hot humid tropics. In its natural habitat the mean maximum temperature of the hottest month is usually 31-33°C and the mean minimum of the coolest month 17-22°C. The area has up to 230 days over 32°C, but few days exceed 38°C. The area is frost-free. Mean annual rainfall is 1300-1750 mm with a strong monsoonal pattern. M. cajuputi grows in a wide range of conditions, but most stands are found on low swampy coastal plains, sometimes immediately behind mangroves that may be flooded to a depth of over one metre during the wet season. The soils are often highly organic alluvial clays with poor drainage and very low fertility, and may be potentially acid sulphate (e.g. the Mekong Delta, Vietnam). It is resistant to fire, tolerates exposure to salt-laden winds, but not to saline waterlogged conditions. In swamps M. cajuputi forms pure forest, mixed open-forest or woodland associated with M. leucadendra (L.) L., Barringtonia acutangula (L.) Gaertn., Lophostemon suaveolens (Sol. ex Gaertn.) Peter G. Wilson & J.T. Waterh. and Nauclea orientalis (L.) L. On less swampy sites it grows with a wide range of eucalypts, acacias and other melaleucas including M. dealbata S.T. Blake, M. saligna Schau. and M. viridiflora Sol. ex Gaertn. Its altitudinal range in Australia is 5-150(-250) m.
By contrast, populations in the Moluccas consist of extensive and mostly pure stands that extend inland on infertile, gravelly ridges with a subsoil of red-brown clay. These sites are often colonized by Imperata grassland. Most ridges and slopes of the northern coastline of Buru and those along the Wai Apu River (which drains to the east coast) have sparse vegetation comprising open woodland and low shrubland of M. cajuputi at 30-400 m altitude, covering some 100 000 ha. In western Seram, M. cajuputi occurs as an almost pure, continuous stand of some 150 000 ha along the Hoamoal Peninsula. Scattered populations occur on lowland plains and low undulating ridges at 30-150 m above sea-level elsewhere in Seram and also on the smaller islands between Seram and Buru. Only a few scattered stands of M. cajuputi have been recorded on Ambon. In Vietnam, M. cajuputi forests once occupied most of the seasonally inundated acid sulphate soils (1.5 million ha) of the Mekong Delta, principally on Ca Mau Peninsula, in the Long Xuyen Quadrangle and on the Plain of Reeds. It is estimated that today only 120 000 ha of natural melaleuca forest remain in the Delta.
Propagation and planting
Propagation of cajeput is usually by seed. Viable seed germinates readily, but the tiny seedlings are easily damaged by overhead watering or rain, or may be killed if the sowing mix dries out. In Vietnam the "bog" technique of watering has been adopted to avoid these problems. This involves standing the germination tray permanently in water so that moisture rises to the surface by capillary action, keeping it constantly moist but not flooded. Seed is sown evenly at a density of about 7000 seeds/m2. An inflated plastic bag is fitted over the container to maintain a moist environment. After about 4 weeks the seedlings are sturdy enough to withstand overhead watering and the container is removed from the water and handled normally. The risk of fungal disease is high, so good hygiene is essential. After germination the tiny seedlings can be slow to develop, but once under way they grow quickly and their total nursery period is 3(-6) months. Plantations have also been established with small stump plants. M. cajuputi can also be reproduced vegetatively from stem and branch cuttings.
In Java, plantations are usually established on degraded land using seedlings of unselected stock at an initial density of 5000 stems per ha. During the first two years plantations may be intercropped with cassava, maize and groundnuts.
On seasonally inundated, acid sulphate soils of the Mekong Delta of Vietnam, weeds are a major problem hampering the establishment of M. cajuputi. If left unchecked the prodigious weed growth becomes a major fire hazard during the dry season. Intercropping ensures adequate weed control. There is some small-scale mulching of plants with the spent leaves left after oil extraction; this practice merits more widespread application. No artificial fertilizers are applied.
Diseases and pests
Young cajeput trees in Java, especially West Java, are attacked by subterranean termites (Macrotermes gilvus, M. insperatus and Odontotermes grandiceps) which attack the bark and wood, causing the trunk to split. Trees whose roots have been attacked may die. Newly planted stumps are most seriously affected. Up to 50% of the trees may be damaged before they are 2 years old. Often as many as 5-6 replantings are needed to replace all dead trees.
In plantations of cajeput in Indonesia trees are allowed to grow for 4 years after planting and are then cut off at about 1 m above the ground at the first harvest of leaves. Thereafter the trees are visited annually and coppice shoots thicker than 1 cm are selectively harvested and leaves and twigs stripped into gunny bags for transport to the distillery. In Central Java some harvesting for oil production takes place throughout the year. However, peak production is during the period June-October which coincides with the best months for oil recovery from leaves and twigs. It is estimated that oil can be economically produced from cajeput plantations for 25 years.
In natural stands in Indonesia harvesting of leaves is a family operation, with groups of 2-6 people involved in the sequential harvesting of family holdings of some 200 ha of M. cajuputi. Coppice growth 1-2 m tall (6-12 months old) is cut by machete and leaves are stripped to fill 20 kg baskets. A skilled cutter can harvest seven baskets per day. The dry season months of May-August are the preferred time of harvest because of reputedly better yield, but harvesting may take place throughout the year.
On the most productive sites, 1 ha of cajeput plantation in Central Java produces about 7.5 t of cajeput leaves annually which gives about 60-65 kg of oil, or a recovery rate of about 0.85%. This yield is reasonable given the extensive management practised. It is widely recognized that yields could be increased dramatically by using genetically superior seed sources and more intensive management practices.
Handling after harvest
The Indonesian State Forest Corporation operates 12 distilleries in Java. There are 4 major and 8 minor factories producing about 280 t of cajeput oil per year from government-run plantations. The industry is labour intensive. In one operation in Central Java based on 3200 ha of plantation, 300 workers are engaged seasonally in the harvesting of leaves and a further 70 people are employed at the distillery. The distillery for this operation comprises 8 stills of 0.9 t capacity each, fed by a steam boiler fuelled by spent leaves of earlier distillations. A 3.5 hour distillation time is standard using a modern, high pressure boiler.
In the Moluccas distillation is done in small traditional stills. The family still is usually a permanent fixture made from mostly local materials. Still capacity is usually about 160 kg of dried leaves and distillation time extends for 8 hours, resulting in 3 kg of oil. Estimates suggest that there are about 100 family stills operating on Buru, 10-12 on Seram and 1-2 operating on each of the islands of Boano, Kelang, Manipa and Ambon.
Once the oil has been separated it should be cleaned of extraneous matter by filtering. Cajeput oil is relatively stable. However, if it is to be stored for any length of time, some of the dissolved water should be removed from the oil by filtering through a bed of anhydrous sodium sulphate. Storage in a cool location away from light is recommended. Oils are best stored in nearly full, glass or stainless steel containers. Head space should be minimal, to reduce oxidation during storage. As it is often impractical to use glass or stainless steel containers for storage and transport, clean drums or cans approved for oil storage are commonly used. Heavily galvanized or epon-lined drums are preferable.
As cajeput is still relatively common throughout its wide geographical range, there are no current conservation concerns, apart from the situation in the Mekong Delta of Vietnam. In this region it is estimated that every year 5000 ha of the 120 000 ha remaining of the once vast Melaleuca forests, are lost through illicit cutting and burning. The wastelands that are created by this process are a priority for reforestation and melaleucas are favoured because they can tolerate the very harsh conditions for tree establishment and growth without expensive mounding.
The wide range of variation in morphology and oil traits of cajeput indicates considerable scope for genetic improvement. Careful selection of well-adapted and fast-growing seed sources of the high-cineole chemotype will be paramount for plantation development aimed at cajeput oil production. In collaboration with the Indonesian Forest Tree Improvement Research and Development Institute, the Australian Tree Seed Centre of CSIRO Forestry and Forest Products is assembling seed collections of M. cajuputi suitable for this purpose. These seedlots will provide the basis for selecting and breeding trees with faster growth rates, higher oil content and higher proportions of 1,8-cineole in the oil than are currently available to the industry.
The immediate future for the cajeput oil industry looks bright, especially in Indonesia where demand for the oil consistently exceeds supply. In Western markets it is likely to remain of minor importance as it is mostly replaced by cheaper eucalypt oil. Major constraints include lack of official quality standards leading to blended and adulterated oils of variable composition, few efficacy or clinical trials to support claims of medicinal benefits, and low yields and quality variation in oils from natural stands and plantations. If plantations are to be more productive on a sustainable basis, tree improvement programmes are needed to enhance biomass production and oil traits. Research is also needed to determine optimal silvicultural methods for oil production without depleting soil nutrients.
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Composition of essential-oil of Cajeput oil, cineole type
Sources of illustrations
Greshoff, M., 1894. Schetsen nuttige Indische planten [Sketches of useful Indonesian plants]. Eerste Serie (1-50). Koloniaal Museum, Extra Bulletin. J.H. de Bussy, Amsterdam, the Netherlands. Fig. 41, p. 176. Redrawn and adapted by P. Verheij-Hayes.