655

19: Essential-oil plants

Cinnamomum camphora (L.) J.S. Presl

Bercht. & J.S. Presl, Prir. rostlin 2: 36, 47—56, t. 8 (1825).

LAURACEAE

2n = 24

Laurus camphora L. (1753), Cinnamomum camphora (L.) Siebold (1830), Cinnamomum camphora (L.) Nees & Ebermaier (1831).

Camphor tree, Japanese camphor tree, Chinese sassafras (En). Camphrier, laurier à camphre (Fr). Indonesia: kamper, kapur barus, nanang. Thailand: opchoai-yuan (general), phromseng (northern). Vietnam: c[aa]y long n[ax]o.

Cinnamomum camphora occurs naturally in Japan, the Ryukyu Islands, China south of the Yangtze river, Hainan, Taiwan and Vietnam. It is cultivated in many tropical and subtropical countries including South-East Asia. It has become naturalized in Australia, where in wetter areas it is considered a weed.

The leaves, wood and roots of Cinnamomum camphora yield essential oils whose main component, camphor, was formerly a very important medicine and disinfectant. Industrially it was a raw material for the production of celluloid, explosives and plasticizers. Medicinally, camphor is used mainly in liniments to relieve chest congestion, muscle pains and arthritis. It was also highly regarded as a cardiac and circulatory stimulant. In traditional medicine it has been an abortifacient, anti-aphrodisiac, contraceptive, cold remedy and suppressor of lactation. Camphor has long been used as an insect repellent, especially of moths in clothing. It was one of the first antiseptics used in hospitals.
The various essential oils obtained from Cinnamomum camphora are important in perfumery mainly as sources of specific aroma chemicals, as fixing agents and in scenting soaps. The heaviest fractions are used as drying solvents in paints and lacquers.
The wood is often considered too valuable to be used as timber, except for cabinet work, such as chests for linen and clothes. The fine odour of the wood and the observation that it repelled insects led to the first extraction of the oil.
In Australia Cinnamomum camphora was first introduced as a shade tree in streets and gardens, but has become a weed in wetter areas of Queensland and New South Wales.

Prior to the First World War, most camphor traded internationally originated from natural stands in Taiwan, Chinese production being used locally. When natural stands became depleted, plantations were established, first in Taiwan and after the Second World War in Japan. Since the 1990s large plantations have also been established in China. Small plantations exist in India and Sri Lanka. No comprehensive information is available on the production and trade in camphor and camphor oils from Cinnamomum camphora. The major producers are Taiwan and Japan. Japan used to produce several thousands of tonnes per year, but production has declined as a result of the manufacturing of synthetic camphor. In 1994 China produced about 1.5 t camphor oil.

Originally, camphor was the most important constituent of the essential oil distilled from the wood of Cinnamomum camphora. Natural camphor is a transparent or whitish, crystalline solid, usually easy to break into pieces and having a characteristic odour. Chemically it is a ketone derivative of a dicyclic terpene; it vaporizes slowly at room temperature, is insoluble in water, but soluble in various alcohols. Camphor is a very toxic substance with a probable human lethal dose of 50—500 mg/kg; low doses cause vomiting, higher doses severe gastrointestinal irritation and convulsions. Its use in non-prescription medicines is considered unacceptable by some. After the introduction of synthetic camphor (similar in appearance to natural camphor, but optically inactive), the importance of natural camphor greatly diminished and the camphor-free residual oil became the main product.
Chemically, Cinnamomum camphora is very variable. Based on analyses of essential oils from China and Vietnam, 8 chemotypes of Cinnamomum camphora have been described, but in international trade 3 main groups of essential oils are generally recognized: 'true camphor oil', 'ho oil' and 'apopin oil'.
'True camphor oil' or 'hon-sho oil' is rarely traded as a complete oil but is usually distilled into several fractions, named white, brown (or red) and blue (or green) camphor oil. White camphor oil is the first fraction distilled and amounts to 20% of the camphor-free oil. Its chief constituent is 1,8-cineole and it also contains other monoterpenoids. White camphor oil is an almost colourless liquid with an eucalypt-like odour. It is rarely used as such in perfumery, but is an important source of perfumery chemicals, including cineole, pinene, terpineol, para-cymene, menthol and thymol. In the United States the Food and Drugs Administration (FDA) classified white camphor oil as 'generally recognized as safe' (GRAS No 2231). The oil is also used as a solvent in the lacquery and paint industry. Brown camphor oil is the medium-heavy fraction amounting to 20—22% of the camphor-free oil and containing about 80% safrole. It is a pale yellow liquid with the characteristic odour of sassafras oil. This is the most important camphor oil in perfumery, because of its great masking effect, e.g. in soap perfumes. One of its components, safrole, is also isolated and then serves as a starting point for the production of heliotropine, vanillin and other perfumery chemicals and a herbicide. The residue after extraction of safrole is traded as yellow camphor oil. An artificial sassafras oil, traded as 'oil camphor sassafrassy', is made from brown camphor oil by rectifying and adjusting the content of safrole and terpenes. Blue camphor oil is the heaviest fraction and is distilled in vacuum from true camphor oil. It has a weak odour consisting mainly of sesquiterpenes, sesquiterpene alcohols and azulenes. It is of minor interest in perfumery, used occasionally for its fixative and masking effect and also finds use as a drying solvent for porcelain paints.
Residual camphor oil may also be characterized by its main component: cineole, safrole, linalool, or terpineol. In general, oil from Taiwan contains mainly linalool or safrole, oil from Japan mainly safrole, and oil from China mainly terpineol and cineole.
'Ho oils' are camphor oils distilled from the wood of forms of Cinnamomum camphora known as 'sho-ho' or 'ho-sho'. The oils are characterized by a high content of linalool. Ho oil from China is generally a complete oil containing camphor and linalool; ho oil from Taiwan and Japan (also named shiu oil) is a fractionated residual oil. The fraction amounts to about 20% of the decamphorized oil.
'Apopin oil' is distilled in China from the most common form of Cinnamomum camphora in China and Taiwan named 'yu-sho' or 'shu-yu'. The crude oil is liquid and does not contain crystalline camphor, but contains about equal amounts of camphor, cineole and terpineol. It is used in China as a low-cost perfume and is also an important source material for the isolation of camphor, cineole and terpineol. Fractions of this oil are used as a basis for the production of very low-priced substitute of eucalypt oil and for adulteration of true eucalypt oil.
Essential oil distilled from the leaves of Cinnamomum camphora is comparable in chemical composition to the residual camphor oil distilled from the wood. Commercially, the most important one is 'ho leaf oil'. Rectified or high-grade ho leaf oil is almost colourless and practically free of camphor-like notes and has a very pure linanool fragrance. The fragrance changes very little on evaporation, but its tenacity is only moderate. It is used in high concentrations in many perfume types. See also: Composition of essential-oil samples and the Table on standard physical properties.

Camphor for industrial purposes is currently made only from turpentine, petroleum derivatives or coal tar. Camphor can also be obtained from the African Ocimum kilimandscharicum Gürke. Camphor oil is a low-priced source of several aroma chemicals that are often used in reconstituting or upgrading other essential oils.

Large, evergreen, fragrant tree, 15(—30) m tall; root system extensive and shallow; trunk short, stout; bark deeply furrowed; crown spreading, up to 30 m wide; twigs brown, yellowish or pinkish when young, glabrous; buds stout, ovoid, pubescent, with many imbricate scales. Leaves alternate, aromatic; petiole slender, 1.5—3 cm long; blade broadly ovate-elliptical to oblong-lanceolate, 5—12 cm x 2—7 cm, base obtuse, margin slightly undulate, apex acute or acuminate, chartaceous, deep green, shiny, glabrous above, glabrous or sparsely hairy beneath, with 3 main veins and 2 conspicuous, impressed glands in vein axils, major veins prominent on both sides. Inflorescence an axillary, many-flowered panicle, up to 7 cm long; pedicel 1—1.5 mm long, glabrous; flowers bisexual, small; perianth tubular, 6-lobed, membranaceous, partly persistent in fruit; lobes ovate, 2.5—3 mm x 1 mm, obtuse, yellowish-green, glabrous outside, pubescent inside, transversely tearing off near the base; fertile stamens 9, in 3 whorls, pubescent; 1st and 2nd whorls eglandular, anthers oblong, 0.5 mm long, introrse; 3rd whorl with 2 subsessile, ovate glands at the base and extrorse anthers; 4th, innermost whorl consisting of 3 eglandular staminodes, ovoid, with short filaments; anthers open upwards by flaps; ovary superior, ovoid, subsessile, glabrous; style up to 2 mm long. Fruit a compressed-globose berry, 7—10 mm in diameter, violet-black when ripe, one-seeded. Seed 6—7 mm in diameter.

Under favourable circumstances trees of Cinnamomum camphora may grow up to 10 m tall with a diameter of 15 cm in 10 years. They may become very old, the oldest specimen known in Taiwan was 1400 years old, the largest tree in Japan is estimated to be 1200 years old. Although it is evergreen, Cinnamomum camphora sheds its leaves annually in spring, but is never leafless. Leaf growth is fast; young flushes are strikingly reddish, whereas new leaves mature in 2—3 months. In East Asia and Australia flowering occurs in spring and fruiting in autumn. Trees start flowering when 7—25 years old; only trees older than 20 years produce viable seed. Outside its natural area of distribution viable seed is produced only occasionally. Fruits are eaten and distributed by birds. Trees coppice well and form root suckers.

There are numerous subclassifications of Cinnamomum camphora, mainly based on the chemical contents of the trees. Although the exact processes regulating the chemistry of the trees are not yet well understood, it is certain that environmental factors such as climate and soil play an important role. Morphologically, however, the differences do not merit special distinction. Once a more stable chemotype classification has been established, the best solution may be a classification into cultivar groups and cultivars. Extensive surveys of essential oils distilled from the wood, leaves and flowers from Cinnamomum camphora in China and Vietnam found a large number of different types of oil; at least 8 chemotypes can be described on the basis of these analyses: a camphor type, a 1,8-cineole type, a linalool type, a camphor-sesquiterpene type, a camphor-1,8-cineole type, a sesquiterpene type, a safrole type, and a phellandrene type.
Cinnamomum pedatinervium Meissner is a 15 m tall tree of the dense, moist forest of Fiji Islands and Micronesia, the bark of which contains safrole. It is also used to prepare a tea and against haemorrhages.
Cinnamomum vimineum C. Nees is a rare species of hill and mountain forests in Peninsular Malaysia and Indonesia and is said to have a strong camphor smell. It is a small tree with lanceolate leaves. Numerous other Cinnamomum species yield essential oils, but are primarily used as spice or timber; many also have medicinal properties.

The natural habitat of Cinnamomum camphora is primary forest, but it occasionally also occurs in open sites, up to 3000 m altitude, though below 1000 m is considered optimal. In West and Central Java it is cultivated at 600—1500 m altitude. It flourishes in warm temperate to subtropical climates, but also under tropical highland conditions. Mature trees can withstand frost to —5°C, but young trees often succumb to it. In its natural habitat annual rainfall ranges between 1000—3500 mm; higher rainfall is tolerated on free draining soils as Cinnamomum camphora with its shallow root system does not tolerate waterlogging. In areas with very high rainfall or after prolonged periods of very heavy rain, the camphor content of the essential oil is low. Unshaded trees have the highest essential oil content. Trees growing in the shade and even shaded leaves of a specific tree usually have lower essential oil and camphor contents. Fertile, well-drained sandy loams are most suitable for cultivation of Cinnamomum camphora. Soil type affects both the essential oil content and its composition. Trees on lighter soils tend to have a higher essential oil content. Neutral to slightly alkaline (pH 6.5—8) soils are preferred for plantations.

Propagation of Cinnamomum camphora is mostly by seed, although propagation by stem and root cuttings and root suckers is also possible. Seed starts to germinate after 3—4 weeks. Seed is normally sown within a few months after collection, as viability after 6 months is usually low. In parts of China with a cold winter, the seed is kept until the following spring. Cleaning and soaking the seed in water for 24 hours improves and hastens germination. Seed is sown in well-prepared and fertilized seedbeds. Germination begins after 3—4 weeks. Seedling plants are ready for transplanting into the field after 12—24 months. Before transplanting they are cut back to 5—10 cm, while in India the roots are also pruned. Planting density is 2000—2500 trees per ha, in some areas even up to 5000 per ha. Where trees are grown for the leaf oil, the chemotype of the planting material is checked by crushing and smelling a leaf.

Plantations of Cinnamomum camphora are managed like most other intensively managed forest plantations. Some weeding is necessary during the first 4—7 years. When grown for the leaves, trees are topped at about 1.5 m and coppiced to encourage a bushy growth. Ideally, fertilizers should then be applied to maintain a good yield, but this is only rarely done. Where a still is located near the plantation, spent leaves are sometimes returned as green manure or mulch.

Many diseases and pests that damage cinnamon (Cinnamomum verum J.S. Presl) also affect Cinnamomum camphora. Diseases generally cause only minor damage. Clitocybe tabescens causing root rot in tropical Asia may affect individual trees. Leaf blight caused by Glomerella cingulata can be controlled to some extent by spraying with a fungicide such as 'benlate'. Acrocercops ordinatella, Attacus atlas, Euproctis lunata and Suana concolor are serious leaf pests in most of Asia, as is the camphor silk moth Dictyoploca japonica. Adults and larvae of the cockchafer Leucopholis pinguis cause considerable damage in nurseries in Asia. The weevil Cratopus punctum is a serious leaf pest in Mauritius.

Formerly, wild trees of Cinnamomum camphora were harvested in a manner similar to timber logging. In plantations, trees are harvested at 16—20-year intervals. Regrowth is normally rapid, as trees coppice readily and vigorously. Plantations to supply leaves are harvested annually in Japan between October and March; in some districts 2 harvests are possible. In India and Sri Lanka up to 4 harvests a year are common. Leaves are generally collected manually, using hand-held strippers or cutters. The feasibility of fully mechanical harvesting is being investigated, but it seems that the shape and the management of the bushes may have to be modified.

Camphor oil used to be obtained by reducing the stems to chips, steam distilling of the chipped wood and then filtering the camphor crystals from the oil. The residual oil was then rectified under vacuum, yielding an additional 50% camphor, and a camphor-free residual oil. Steam distillation of the leaves to extract camphor was first developed in the United States and was later adopted in Japan and Taiwan, when natural stands of mature Cinnamomum camphora trees became depleted.

Small collections of germplasm of Cinnamomum camphora exist but cover only a small part of the natural range and the variation in chemotypes. The segregation of the progenies of different chemotypes is being studied, as a first step in the development of high quality strains with specific essential oil characteristics.

Although natural camphor is no longer used industrially, the essential oils distilled from Cinnamomum camphora remain important as they yield several other components that are important for the industrial manufacture of aroma compounds. The various compounds, rectified essential oils and fractions will remain important in low-price perfumery, in soap perfumes, and as fixing agents in compounded perfumes because of their low price and easy and regular supply. The most important medicinal role of camphor will probably continue to be in rubbing liniments.

Committee on Drugs (United States), 1978. Camphor, who needs it? Pediatrics 62: 404—405.
Craker, L.E. & Simon, E., 1986—1988. Herbs, spices and medicinal plants. Recent advances in botany, horticulture and pharmacology. Oryx Press, Phoenix, Arizona, United States.
Dung, N.X., Khieu, P.V., Chien, H.T., Leclercq, A.X. & Leclercq, P.A., 1998. Chemical segregation of progeny of camphor trees with high camphor c.q. linalool content. Journal of Essential Oil Research (in press).
Ibrahim bin Jantan & Goh, S.H., 1992. Essential oils of Cinnamomum species from Peninsular Malaysia. Journal of Essential Oil Research 4: 161—171.
Liao, Jih-Ching, 1996. Lauraceae. In: The Editorial Committee of the Flora of Taiwan: Flora of Taiwan, Vol. 2, Second Edition. Department of Botany, National Taiwan University, Taipei, Taiwan. pp. 437—448.
Nguyen Xuan Dung, Pham Van Khien, Ho Trung Chien & Leclercq, P.A., 1993. The essential oil of Cinnamomum camphora (L.) Sieb. var. linaloolifera from Vietnam. Journal of Essential Oil Research 5: 451—453.
Sastri, B.N. (Editor), 1950. The wealth of India. A dictionary of Indian raw materials and industrial products. Vol. 2. Cinnamomum. Publications and Information Directorate, Council of Scientific and Industrial Research, New Delhi, India. pp. 173—183.
Weiss, E.A., 1997. Essential oil crops. CAB International, Wallingford, United Kingdom. pp. 156—168.
Zhu, L.F., Ding, D.S. & Lawrence, B.M., 1994. The Cinnamomum species in China: resources for the present and future. Perfumer and Flavorist 17(4): 17—22.

F. Indah Windadri & S.S. Budi Rahayu

Windadri, F.I. & Rahayu, S.S.B., 1999. Cinnamomum camphora (L.) J.S. Presl. In: L.P.A. Oyen and Nguyen Xuan Dung (Editors): Plant Resources of South-East Asia No 19: Essential-oil plants. PROSEA Foundation, Bogor, Indonesia. Database record: prota4u.org/prosea