Pogostemon (PROSEA)

Plant Resources of South-East Asia Introduction

List of species

Pogostemon cablin - 1, flowering branch; 2, inner surface of dissected calyx; 3, dissected corolla with stamens; 4, inner surface of bract.

Pogostemon Desf.

Protologue: Mém. Mus. Hist. nat. Paris 2: 154 (1815).

Family: Labiatae

Chromosome number: x= 16; P. cablin: 2n= 32, 34, 64; P. heyneanus: 2n= 32, 64.

Major species and synonyms

• Pogostemon cablin (Blanco) Benth., in: A. DC., Prodr. 12: 156 (1848), synonyms: Pogostemon patchouly Pellet. (1845), P. comosus Miquel (1859), P. javanicus Backer ex Adelb. (1954).

• Pogostemon heyneanus Benth., in: Wallich, Pl. asiat. rar. 1: 31 (1830), synonyms: Origanum indicum Roth (1821), Pogostemon patchouli sensu Hook.f. (1885), non Pellet. (1845).

Vernacular names

P. cablin :

• Patchouli (En).
• Patchouli (Fr)
• Indonesia: nilam wangi (general), nilam (Aceh), singalon (Batak)
• Malaysia: dhalum wangi, tilam wangi
• Philippines: kabling (Tagalog), katluen (Bisaya), kadlum (Bikol, Bisaya, Sulu)
• Thailand: phimsen (Bangkok)
• Vietnam: hoắc hương.

P. heyneanus :

• Indian patchouli, Java patchouli (En)
• Indonesia: dilem (Sumatra), dilem kembang (Javanese), dhilep (Madurese)
• Malaysia: boon khalif, nilam bukit, pakochilam
• Philippines: kadlum (Bisayas), lagumtum, malbaka (Subanun).

Origin and geographic distribution

Pogostemon comprises about 80 species occurring throughout South and South-East Asia up to China and Japan, with 1 species extending into Australia. The origin of P. cablin is uncertain, the border region between South-East Asia and China has been suggested as its origin, and the Philippines as a secondary centre of diversity. It is widely distributed in South and South-East Asia and has been introduced all over the tropics and subtropics. Cultivation of P. cablin for its essential oil probably started in Penang (Malaysia) in the 19th Century using plants from the Philippines. From there it was taken to Java in 1895 and to Sumatra in 1910. By 1920 production was well established in Aceh (northern Sumatra). It is mainly cultivated for the production of essential oil in Sumatra (Indonesia), southern China and Brazil and to a lesser extent in India, the Seychelles, Madagascar, and Taiwan. P. heyneanus is widespread in South and South-East Asia, from southern India and Sri Lanka to Indonesia and the Philippines, but it is probably not native to Malesia. It is cultivated for its fragrant leaves in South and South-East Asia and also outside this region (e.g. in the Seychelles).

Uses

Pogostemon has a long history of use in southern Asia and the Far East as incense, body and garment perfume and as a repellent of insects and leeches. In China, where it was probably grown 2000 years ago, ink was also perfumed with it. Traditionally, the dried leaves of several Pogostemon species are placed between stored clothing to repel insects and to impart a pleasant smell. Through the import of Indian shawls and clothing the fragrance became well known in Europe, but not until 1844 did the first dried leaves arrive in London. Cloth producers in France were then quick to copy the practice.

Patchouli oil steam distilled from P. cablin leaves is almost universally used as a fixing agent in perfumery, blending beautifully with an exceptionally wide range of fragrance and body-care materials. It is mostly used in very small dosages, but in Oriental-type perfumes it is often a fundamental note. Its odour has a masking effect when used in depilatory creams. Combined with other flavour materials, it is an important ingredient in Oriental-type after-dinner candies, appreciated for their masking effect on alcoholic, onion and garlic odours. Recently, patchouli oil has become one of the additives to cigarettes and tobacco as one of the components added to compensate the loss of taste due to a reduced tar content. In Goa the inflorescence of P. cablin is sold to dress the hair of women.

P. heyneanus is widely cultivated for its fragrant leaves, but mostly on a minor scale. An essential oil distilled from the leaves in Java is much inferior to patchouli oil and its production has been abandoned. Small quantities are occasionally produced in India for local use or as an adulterant for patchouli oil. In Java crushed leaves of P. heyneanus were formerly used to wash clothes.

Pogostemon species have many uses in traditional medicine. In Chinese medicine a decoction of the leaves is used with other drugs to treat nausea, vomiting, diarrhoea, colds and headache. In the Philippines an infusion of the leaves is taken to allay painful menstruation. In Japan and Malaysia patchouli oil is erroneously considered an antidote to snakebite. In Thailand a preparation of equal parts of P. cablin leaves, guava and orange peel is recommended against diarrhoea. In aromatherapy it is used as a relaxant. Leaves are added to bath water to alleviate rheumatism. P. heyneanus is used as a carminative and diuretic.

Production and international trade

World production of patchouli oil has grown steadily and had reached about 1000 t/year in 1995. Over 80% of the annual world production comes from Sumatra, where P. cablin is cultivated on over 18 000 ha. Between 1985-1995 Indonesia exported 350-850 t annually. China produces about 60 t/year and Brazil, Malaysia and the Seychelles produce smaller quantities. In 1995, the United States alone imported about 500 t with a value of US$ 20 million. The price of patchouli oil in Indonesia is about US$ 50 per kg (1998).

Properties

Indonesian-distilled patchouli oil is a dark orange or brownish, viscous liquid with a tenacious, extremely rich, sweet-herbaceous, aromatic-spicy and especially earthy, woody-balsamic odour. Good quality patchouli oil has an ethereal-floral, wine-like sweet top note, that is, however, often absent in freshly distilled, otherwise good oils. Sweet notes, present in all stages of evaporation, are very persistent and remain perceptible on a perfumer's blotting paper for months. Their intensity is so great that high concentrations are nauseating to many people. The top note is sometimes reminiscent of the aroma of cade oil (from Juniperus oxycedrus L.) and cedarwood oil (from Cedrus libani A. Rich. subsp. atlantica (Endl.) Battand. & Trabut). This top note is useful for specific purposes, but not generally considered desirable. Occasionally the top note has distinct, but undesirable tar-like characteristics. The body notes of good quality patchouli oil should be outstandingly rich, with a delicate, root-like earthiness, without mouldy or musty notes. Because of variations in the composition of the oil, many other notes have been described, e.g. minty, swampy and barnyard-like.

Patchouli oil distilled in Europe or the United States is a pale orange or amber-coloured, viscous liquid. Its odour resembles that of Indonesian-distilled patchouli oil, but has a more pronounced fruity, wine-like top note and less pronounced woody-balsamic notes. Moreover it is generally more tenacious. The difference between the two types of oil may be caused by the dried leaves curing during transport and storage before distillation in Europe or the United States. Both patchouli oils improve on ageing, losing the sharp-green or wet-earthy and minty notes.

Patchouli resinoid or concrete is a benzene or petroleum-ether extract of P. cablin leaves. Its character is similar to that of patchouli oil distilled in Europe or America. On alcohol distillation the petroleum ether extract yields an absolute that captures the essence of the patchouli odour. The main chemical components of patchouli oil are patchouli alcohol, guaiene, patchoulene and seychellene. Other characteristic compounds are norpatchoulenol, nortetrapatchoulol,α-cedrenal and several pyridine derivatives. P. cablin from different origins and different cultivars may yield oils of divergent composition, e.g. a cultivar from Tsukuba (Japan) grown in the southern Philippines yielded an oil poor in guaiene and rich in longifolene (possibly a misidentification for seychellene, which is a common constituent of patchouli oil). Dhelwangine (pogostone), a minor constituent of P. cablin , is reported to have antibiotic activity against fungi and bacteria and is responsible for the bactericidal properties of patchouli oil. In preliminary tests in the Philippines, spraying potatoes with a low concentration of patchouli oil solution effectively inhibited sprouting for up to 4 months.

In the United States patchouli oil has been approved for food use by the Food and Drug Administration under paragraph 172.510 and has been "generally recognized as safe" (GRAS No 2838). As a flavour ingredient, use levels of the oil are mostly less than 2 ppm. A monograph on the physiological properties has been published by the Research Institute for Fragrance Materials (RIFM). The essential oils from other Pogostemon species are poorly known. See also: Composition of essential-oil samples and the Table on standard physical properties.

Adulterations and substitutes

Essential oils extracted from several other plants are sold as patchouli oil, e.g. Chinese patchouli (Microtoena insuavis (Hance) Prain ex Briquet (synonyms: Plectranthus patchouli C.B. Clarke ex Hook.f., Microtoena cymosa Prain). P. cablin leaves for export used to be frequently mixed with leaves of P. heyneanus, Microtoena insuavis, Ocimum basilicum L. or Urena lobata L. There are synthetic patchouli substitutes, but these are expensive and do not have the broad odour profile of the true essential oil. Sometimes, solvents that have a high boiling point, such as benzyl benzoate and propylene glycol are added as extenders to adulterate patchouli oil.

Description

• Usually pubescent, sometimes strongly scented, herbs or small shrubs.
• Leaves opposite or whorled, petiolate or sessile, often doubly crenate-serrate.
• Inflorescence a verticillaster, arranged in simple or branched, axillary or terminal, often densely flowered false spikes or racemes, which again are often united into a terminal panicle; bracts and bracteoles small, densely hairy, persistent.
• Flowers small; calyx campanulate-tubular, 5-veined, ending in 5 subequal teeth; corolla tubular, shortly 2-labiate, 4-lobed, 3 lobes forming upper lip, lower lip entire; stamens 4, exserted from the corolla, often in 2 pairs, divaricating, filaments usually pilose, anthers unilocular; disk subentire; ovary deeply 4-partite, glabrous; style exserted, 2-lobed at apex.
• Fruit consisting of 4 smooth or granulate, glabrous nutlets, enclosed in the persistent calyx.

P. cablin.

• Erect or ascending aromatic herb, up to 1 m tall. Stem branched, solid, angular, tomentose.
• Leaves decussately opposite, thin- or thick-membranaceous, with short appressed hairs; petiole 1-3(-8) cm long; blade ovate, 5-10(-14) cm × 3.5-6.5(-10) cm, base cuneate, margin simple or double crenate-serrate, apex acute, gland-dotted below.
• Spicate racemes 3-many, forming a terminal panicle 15-30(-40) cm long; verticillasters slightly apart below, closely approximate above, grey pubescent; bracts ovate to lanceolate, up to 9 mm × 4 mm, entire to toothed, imbricating.
• Calyx tubular, 4-6 mm long, densely hairy outside, subglabrous inside, teeth about 2 mm long and ciliate; corolla 6-7 mm long, white, lavender-blue or violet; filaments inserted at about 2 mm in the tube, about 6 mm long, violet, soft-haired but glabrous towards the base; style 6 mm long, lobes 1.5-2 mm long.
• Nutlets ellipsoidal, 0.6-1 mm × 0.5-0.6 mm, reticulate-punctate, black.

P. heyneanus.

• Erect or ascending, aromatic subshrub, up to 1.5 m tall. Stem branched, slender, solid, obtusely 4-angular, subglabrous and rooting at the base, short-haired in upper part.
• Leaves decussately opposite, thin-membranaceous, subglabrous to rather densely soft-haired; petiole 1-6 cm long; blade ovate, 1-14 cm × 1-8 cm, base cuneate, margin simple or double crenate-serrate, apex acuminate, gland-dotted below.
• Inflorescence paniculate, terminal, 6-18 cm long; verticillasters globular, 0.5-1.5 cm apart at the base, more approximate upwards; bracts ovate to lanceolate, 3-5 mm long.
• Calyx tubular, 3-5 mm long, tomentose outside, subglabrous at base inside, teeth triangular, 1-1.5 mm long, ciliate; corolla 4-5 mm long, white or with pale violet upper lip, glabrous; filaments inserted at about 1.7 mm in the tube, straight, about 4 mm long, bearded around the middle but glabrous towards the base; style 5-6 mm long, lobes 0.6-0.7 mm long.
• Nutlets orbicular, 0.5-0.6 mm long, reticulate-punctate, shiny black.

Growth and development

In cultivation P. cablin rarely flowers; only in the Philippines and in China, where it occurs wild, does it flower freely. In the Philippines flowering is between May to February, in southern China in April. P. heyneanus flowers year round.

Other botanical information

The taxonomy of especially the cultivated Pogostemon species such as P. benghalensis (Burm.f.) Kuntze (northern India to China), P. cablin, P. heyneanus, and P. plectranthoides Desf. (Indian subcontinent) is not well investigated. These species are often propagated vegetatively and several cultivars seldom or never flower. It is possible that most cultivars belong to one botanical species.

Besides these 4 species which all produce a kind of patchouli oil, several other ones are also known to produce essential oils which are, however, mainly used medicinally. These include P. auricularius (L.) Hassk. (India, China, throughout South-East Asia), P. glaber Benth. (from India and Nepal to China and Thailand), P. menthoides Blume (from India to Indonesia), P. purpurascens Dalzell (India) and P. verticillatus (Roxb.) Bhatti & Ingr. (aquatic plant, from India and China throughout South-East Asia to Australia).

In Java, a cultivated Pogostemon occurs which is named "dilem Java", and which also has never been found in flower. It has tentatively been named Pogostemon hortensis Backer ex Adelb., but it is most probably a cultivar of P. cablin with a more vigorous growth. It yields an essential oil inferior to patchouli oil.

Although Pogostemon plants are traded commercially, named cultivars are rarely used. In India 5 introduced cultivars of P. cablin have been named after their origin: "Indonesian", "Java", "Johore", "Malaysian" and "Singapore". "Java" and "Singapore" have a high yield potential but produce oils of inferior quality; the oil from "Indonesian", "Johore" and "Malaysian" produce oils matching the quality of fine internationally traded oils.

Two types of oil glands occur in the leaves of P. cablin : glandular trichomes on the epidermis and mesophyll glands. The glandular trichomes consist of a large (16μm × 27μm) secretory head, a stalk of several cells and a basal cell embedded in the epidermis, but different from the normal epidermis cells. This type of secretory trichome is common in Labiatae. The mesophyll glands are complex structures located in the palisade tissue or occasionally in the spongy parenchym. They consist of a large (30μm × 38μm) secretory cell located near a small vascular bundle. The secretory cell has very dense cytoplasm and a large nucleus and is surrounded by a cuticula. The essential oil produced is contained in the space between the cell wall and the cuticula. The vascular bundles associated with the secretory cells consist of xylem and phloem elements, idioblasts and bundle sheath cells. In in vitro cultures of P. cablin tissues or cells, which do not contain mesophyll glands, no cyclic sesquiterpenes, which are characteristic of patchouli oil, are produced.

Ecology

P. cablin can adapt to a wide range of climate and soil conditions. For optimal growth it requires a damp and per-humid climate with an evenly distributed annual rainfall of 2000-3000 mm, a drier season of not more than 12-14 weeks, and average temperature of 22-28°C. For commercial production an annual rainfall of 1750-2000 mm is suitable, but below 1500 mm supplemental irrigation is required. P. cablin is probably not tolerant of frost, but can be grown in the tropics up to 2000 m altitude. Relative humidity should be high; a minimum monthly average of 75% is considered essential for sustained growth in Indonesia. Continuous bright sunshine can damage young plants, resulting in dwarfing and yellowish leaves. Although P. cablin tolerates intermittent shade, intercropping in established rubber or coconut plantations leads to poor vigour and regrowth and to reduced leaf-oil content. The risk of damage by nematodes is also high when planted as an intercrop. Intercropping in newly established rubber or coconut plantations, however, has been recommended in Indonesia, Malaysia and India. P. cablin can grow on a wide range of soils, but very fertile soil is required for commercial production. Where possible it is planted on newly cleared forest land. Tolerance of waterlogging is poor, 3-4 days of standing water may kill young plants.

P. heyneanus occurs in thickets, old clearings, coconut plantations and stream banks, from sea-level up to 1800 m altitude.

Propagation and planting

P. cablin is propagated vegetatively by cuttings. In Indonesia cuttings 5-10 cm long are taken from the central part of semi-mature stems. Cuttings from 9-month-old plants give the highest success rate. Alternatively, 10-12 cm long cuttings with 3 or 4 nodes and a terminal bud are used. Cuttings are planted in nursery beds and transplanted into polybags after 3-5 weeks. Rooted cuttings are planted out in the field at a spacing of about 60 cm × 60 cm. Cuttings are sometimes planted directly into the field using cuttings 15-20 cm long and planting them at an angle of 60° to the soil surface at a rate of 2-3 per hill. Adequate moisture and shade are essential during the early stages. When propagation material is scarce or when selected plants are multiplied, 2.5-5 cm long, single-node cuttings can be used, provided the nodes are buried in the rooting medium. In vitro multiplication using stem meristems has been successful in India and the Philippines. In this procedure plantlets are formed directly from meristem tissue and not from callus, which reduces the risk of mutations. The procedure involves hormone treatments to induce stem formation and shoot growth; to promote root growth, the plantlets are transferred to hormone-free medium. Plants developed from these plantlets grow well and yield an essential oil of normal composition.

P. heyneanus can easily be propagated by seed and by cuttings.

Husbandry

During the 2-3 months immediately after planting of Pogostemon until the canopy closes and weeds are suppressed, 2-3 weedings are required. Weeding is also necessary in the first month after harvesting.

As large amounts of plant nutrients are removed with the harvested leaves and as P. cablin is very sensitive to nematode infestation, it is mostly grown on virgin forest land or as the first crop after fallow. Dwarfing and yellowing of the leaves caused by continuous bright sunshine can be mitigated by the application of N fertilizer. The highest yields are obtained under 25-50% shade in combination with N fertilizer. In India, application of 40 kg N, 15 kg P and 15 kg K per ha at planting time gave the best economic results. Topdressing with 25 kg N after about 8 weeks and twice after each harvest is recommended.

Diseases and pests

Pogostemon is affected by several fungi attacking the roots and leaves. Alternaria and Cercospora spp. may cause extensive damage to the leaves. Fomes, Pythium and Sclerotium spp. may affect the root system; Fomes is especially serious where P. cablin is interplanted in rubber plantations.

Nematodes, particularly Heterodera marioni in Indonesia and Helicotylenchus dihystera and Meloidogyne incognita in India cause extensive damage in Pogostemon. In some cases infestation is so serious that it reduces crop life and causes replanting to be unprofitable unless a long fallow or rotation period is observed. Pogostemon is often affected by viruses. Patchouli mottle virus (PaMoV, a potyvirus), patchouli mild mosaic virus (PaMMV, a faba-group virus) and tobacco necrosis virus (TNV) have been isolated. Virus-free plants can be produced by meristem-tip culture. Increased biomass and oil yields of virus-free plants have been reported, while the quality of the oil produced was very similar to that obtained from the original material. The rate of reinfection in the field can be high; 30% in 4 months has been observed.

Few pests cause serious damage. Crickets, grasshoppers and snails have been reported to affect Pogostemon, but they can be controlled easily. Leaf-rolling caterpillars are a more serious pest, as they are difficult to control.

Harvesting

The first harvest of Pogostemon is usually taken when the plants are 6-8 months old, having attained a height of 0.5-1 m. The best quality oil is obtained from leaves harvested in the wet season. Subsequent harvests, if possible also in wet periods, are taken every 3-5 months until the crop is about 3 years old, when yield and quality of the oil decrease. Harvesting should not be done when leaves are saturated following rain or from morning dew. When harvesting during hot dry periods, cutting in the morning or evening is preferable. Plants are cut 10-20 cm above the ground. In Indonesia it used to be recommended to harvest only the top 3-5 pairs of leaves. Such selective harvesting is still possible for small farmers, as this system allows rapid regrowth and a regular supply of leaves to small local stills.

Yield

In Indonesia 1 ha of Pogostemon yields 40-60 kg patchouli oil.

Handling after harvest

Stems and leaves of Pogostemon are dried for 2-5 days on wooden racks, hard-packed earth or a concrete floor. The method of drying and subsequent curing strongly influence the quality of the oil. Drying in the shade with ample ventilation is preferable, but sun-drying is common. Sun-drying may cause leaves to become overdried and brittle. This results in loss of oil, while small fragments and dust from shattered leaves are difficult to handle in stills. A drying temperature over 40°C in Malaysia resulted in 80% loss of oil. After drying, leaves are stripped from the stems and packed under humid conditions in woven baskets or steel drums for curing. Skilled growers can control the curing process by smelling the leaves. Over-fermentation produces a mouldy note in the oil, under-fermentation reduces oil yield. In Malaysia leaves are not deliberately cured by the grower, but only packed in bags. Curing takes place during transport to the still and in storage. For export, leaves are dried and pressed into bales. Bales store well provided they are kept clean and dry. The long period of curing during transport and storage may explain the high quality of oil distilled in Europe or the United States.

In small-scale production, direct-fired stills are used in which leaves are placed on a perforated plate or grille above the water level. It takes 6-8 hours to distill a charge of 75-100 kg, but distillation is sometimes prolonged to up to 24 hours as the most desirable fractions are the last to distill over. Yields of essential oil are strongly influenced by the intensity of distillation. A still with an open wire grille yields significantly more oil than one with a perforated steel plate. Distillation temperature affects the yield, but not the quality of the essential oil. In Indonesia, raising steam temperature from 100°C to 200°C increased yield from 1.3% to 2.2%. After distillation patchouli oil is stored to mature. The quality of the oil improves in storage.

Genetic resources and breeding

No substantial germplasm collections of Pogostemon are known to exist. At the Indian Institute of Horticultural Research, Bangalore a research programme is in progress aiming at high oil yields and with emphasis on the induction of mutations to increase genetic variability.

Prospects

Research on disease and pest management is urgently needed to enhance the longevity of Pogostemon crops. Collection and thorough inventory of germplasm followed by selection programmes would also contribute to increased yields of oils of higher quality. Although it has been claimed that synthetic patchouli oils can match the odour of genuine oils, no effective substitutes for high quality perfumes have yet been developed.

Literature

• Angadi, S.P. & Vasantha Kumar, T., 1995. In: Chadha, K.L. & Gupta, R. (Editors): Advances in Horticulture. Vol. 11. Medicinal and aromatic plants. Malhotra Publishing House, New Delhi, India. pp. 751-771.
• Keng, H., 1978. Labiatae. Pogostemon. In: van Steenis, C.G.G.J. (Editor): Flora Malesiana. Vol. 8. Sijthoff & Noordhoff International Publishers, Alphen aan den Rijn, the Netherlands. pp. 351-356.
• Lawrence, B.M., 1995. Progress in essential oils. Perfumer and Flavorist 20: 67-73.
• Maeda, E. & Miyake, H., 1997. Leaf anatomy of patchouli (Pogostemon patchouli) with reference to the disposition of mesophyll glands. Japanese Journal of Crop Science 66: 307-317.
• Raza Bhatti, G. & Ingrouille, M., 1997. Systematics of Pogostemon (Labiatae). Bulletin of the Natural History Museum (London), Botany Series 27: 77-147.
• Reglos, R.A. & de Guzman, C.C., 1991. Morpho-physiological modifications in patchouli, Pogostemon cablin (Blanco) Benth., under varying shade and nitrogen levels. The Philippine Agriculturist 74: 429-435.
• Soepadyo, R. & Tan, H.T., 1968. Patchouli, a profitable catch crop. World Crops 3: 48-54.
• Sugimura, Y., Ichikawa, Y., Otsuji, K., Fujita, M., Toi, N., Kamata, N., del Rosario, R.M., Luingas, G.R. & Taga-an, G.L., 1990. Cultivarietal comparison of patchouli plants in relation to essential oil production and quality. Flavour and Fragrance Journal 5: 109-114.
• Sugimura, Y., Padayhag, B.F., Ceniza, M.S., Kamata, N., Eguchi, S., Natsuaki, T. & Okuda, S., 1995. Essential oil production increased by using virus-free patchouli plants derived from meristem-tip culture. Plant Physiology: 44: 510-515.
• Weiss, E.A., 1997. Essential oil crops. CAB International, Wallingford, United Kingdom. pp. 138-154.

Composition of essential-oil of Patchouli oil (from Java) (Pogostemon cablin)

• 26.7% patchouli alcohol
• 16.7% α-bulnesene
• 13.5% α-guaiene
• 8.8% seychellene
• 4.5% α-patchoulene
• 4.2% β-caryophyllene
• 2.4% δ-cadinene
• 2.3% pogostol
• 2.0% β-patchoulene
• 0.9% caryophyllene oxide
• 0.8% norpatchoulenol
• 0.7% β-elemene
• 0.4% α-gurjunene
• 0.3% β-pinene
• 0.3% 1,10-epoxy-α-bulnesene
• 0.2% cycloseychellene
• 0.1% α-pinene
• 0.1% 1,5-epoxy-α-guaiene
• 87.7% total

Source: Lawrence, 1990.

Physical properties of essential oil

patchouli oil (Pogostemon cablin)

• Relative density : 0.955-0.983
• Refractive index : 1.505-1.512
• Optical rotation : -66° to -40°
• Miscibility in ethanol : 1:10 (90%)
• ISO/EOA : ISO 3757 '78

See comments : Physical properties of essential oils (PROSEA)

Sources of illustrations

Brown, W.H., 1957. Useful plants of the Philippines. Vol. 3. Department of Agriculture and Natural Resources. Technical Bulletin No 10. Bureau of Printing, Manila, the Philippines. (reprint of the 1943 edition). Fig. 110, p. 295 (flowering branch); Raza Bhatti, G. & Ingrouille, M., 1997. Systematics of Pogostemon (Labiatae). Bulletin of the Natural History Museum London (Botany) 27: 77-147, Fig. 5(b), p. 93 (calyx, corolla, bract). Redrawn and adapted by P. Verheij-Hayes.

Authors

L.P.A. Oyen