AN OVERVIEW OF ESSENTIAL OIL BEARING PLANTS OF NEPAL

Khilendra GurungE-mail: khilendragurung@yahoo.com

Introduction:Nepal harbors rich flora due to the presence of wide range of geographical and climatic conditions. The floral diversity comprises about 6500 species of flowering plants and 28 species of gymnosperms (Chaudhary, 1998 and Press et al., 2000). Nature has endowed it with over 700 species of medicinal plants (DPR, 1976) and over 200 species of aromatic plants (Adhikary, 1989). The presence of ecological zones ranging from tropical to alpine has created the potentiality for the cultivation of a wide variety of exotic species of essential oil bearing aromatic plants in Nepal (Rawal and Pradhan, 1996). Essential oils are chemical compounds with an odoriferous nature which are highly volatile, insoluble in water but soluble in organic solvent. They are obtained from herbs, flowers, woods, leaves and seeds including spices, by steam distillation or solvent extraction. 'Essential' refers to the presence of an essence or odor and the term 'oil' is used due to the retention of oil spot when they are placed on a transparent paper. The families Pinaceae and Cupressaceae among the gymnosperms; Apiaceae, Myrtaceae, Rutaceae, Lauraceae, Lamiaceae, Asteraceae (dicots) and Poaceae, Araceae, Zingiberaceae and Amarylidaceae (monocots) among angiosperms, account for a large number of aromatic plants bearing essential oils of commercial importance.The utilization of essential oil is very extensive and covers a wide range of human activity. Some of the important uses are as; ingredients in the manufacture of soaps, cosmetics, perfumery, health care herbal products, confectionary, aerated water, syrups, disinfectants, insecticides, fungicides, paper writing pads, greeting cards etc.

Present status:The world's total production of essential oil is estimated at about 1,00,000 to1,10,000 tons (Farooqi and Sreeramu, 2001). But, Nepal shares a negligible percentage of essential oil in terms of production despite its rich aromatic floral diversity. Most of the essential oil produced is exported, while few amounts are marketed within the country. This oil is very expensive and earns good revenue in terms of foreign exchange. Most of the essential oil bearing aromatic plants are distributed throughout the country. While few plants are cultivated in farmlands, community forests and in marginal lands. Major essential oil

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produced and these bearing plants of Nepal are summarized in Table 1.

Table 1: Essential oil bearing plants and their distribution in NepalSN

Essential oils

Botanical name / Parts used

Active constituents Distribution in Nepal

1 Abies oil Abies spectabilis / Needles and young twigs

Pinene, limonene WCE, alt, 2100-3600m

2 Anthopogon oil

Rhododendron anthopogon / Leaves and young twigs

a-pinene, b-pinene, limonene and δ-cadinene

WCE, alt.3300-5100m

3 Artemisia oil Artemisia vulgaris / Leaves and flowering tops

Thujone, cineol, pinene WCE, alt.1000-2400m

4 Basil oil (French)

Ocimum basilicum / Flowering herbs

Methyl chavicol (70-88%), linalol

WCE, alt, 300-1500m (cultivated)

5 Calamus oil Acorus calamus / Rhizomes and roots

Beta-asarone (up to 80%), calamene, calamol

WCE, alt, 300-2700m

6 Camphor oil Cinnamomum camphora / Leaves

Cineol with pinene C, alt, 1300-1500m

7 Cedar wood oil

Cedrus deodara / Woods and saw dust

Cedrol, cadinene W, alt, 2400-3700m

8 Chamomile oil Matricaria chamomilla / Flowers

Chamazulene, azulene (1-15%)

CE, alt, 500-1500m (cultivated)

9 Cinnamon oil Cinnamomum tamala / Leaves and twigs

Eugenol (80-96%), cinnamaldehyde (3%)

WCE, alt, 450-2000m

10 Citronella oil Cymbopogon winterianus / Partially dried grass

Citronellol (upto50%), geranial (upto45%)

WC, alt, 400-2000m (cultivated)

11 Clove oil Syzygium aromaticum / Buds and leaves

Eugenol (60-90%), eugenol acetate

WCE, alt, 300-1000m (cultivated)

12 Coriander oil Coriandrum sativum / Crushed ripe seeds

Linalol (55-75%), decylaldehyde

WCE, alt, 200-1500m (cultivated)

13 Corn mint oil Mentha arvensis / Flowering herbs

Menthol (70-95%), menthone (10-20%)

WCE, alt, 300-2000m (cultivated)

14 Cumin oil Cuminum cyminum / Ripe seeds

Cuminaldehyde (upto60%), pinene, terpinene

WCE, alt, upto800m (cultivated)

15 Curcuma oil Curcuma zedoaria / Rhizomes Tumerone (60%), zingiberene

CE, alt, 700-1500m (cultivated)

16 Eucalyptus oil Eucalyptus camaldulensis / Leaves and young twigs

Cineol (70-85%), pinene

CE, alt, 400-1500m (cultivated)

17 Garlic oil Allium sativum / Crushed bulbs

Allicin WCE, alt, 1000-2600m (cultivated)

18 Ginger oil Zingiber officinale / Rhizomes Gingerin, gingenol, zingiberene

WCE, alt, 150-1200m (cultivated)

19 Hemlock oil Tsuga dumosa / Needles and twigs

Pinene, limonene, bornyl acetate

WCE, alt, 1800-3500m

20 Jasmine oil Jasminum officinale / Flowers Benzyl acetate, linalol, cis-jasmone

CE, alt, 800-1800m

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(cultivated)21 Jatamansi oil Nardostachys grandiflora /

Rhizomes and rootsBornyl acetate, isobornyl valerianate

WCE, alt, 3200-5000m

22 Juniper oil Juniperus communis / Berries and needles

Pinene, myrcene, sabinene

WCE, alt, 3000-4100m

23 Lemon oil Citrus aurantifolia / Peel of fruits

Limonene, pinene, camphene

CE, alt, 600-1500m (cultivated)

24 Lemongrass oil

Cymbopogon flexuosus / Partially dried leaves

Citral (65-85%), myrcene (12-25%)

WCE, alt, 300-1100m (cultivated)

25 Marigold oil Calendula officinalis / Flowers Calendulin CE, alt, 300-1500m (cultivated)

26 Orange oil Citrus reticulata / Peel of fruits Limonene, myrcene, camphene

CE, alt, 600-1500m (cultivated)

27 Palmarosa oil Cymbopogon martini / Partially dried grass

Geraniol, farnesol CE, alt, 900-2000m (cultivated)

28 Peppermint oil

Mentha piperita / Flowering herbs

Menthol (29-48%), menthone (20-31%)

WCE, alt, 1200-2700m (cultivated)

29 Pine oil Pinus roxburghii / Needles and twigs

Alpha pinene (50%), beta pinene (25-35%), carene (20-60%)

WCE, alt, 600-1800m

30 Rose oil Rosa spp. / Fresh petals Citronellol (20-35%), nerol (30-40%), geraniol

WCE, alt, 1200-3000m (cultivated)

31 Sage oil Salvia officinalis / Dried leaves Thujone (upto42%), cineol, borneol

WCE, alt, 500-1500m (cultivated)

32 Sandalwood oil

Santalum album / Heartwoods Santalols (90%), santene, teresantol

W, alt, 200-900m

33 Sugandhakokila oil

Cinnamomum glaucescens / Berries

Methyl cinnamate, cineol

WE, alt, 2000-2500m

34 Tagetes oil Tagetes minuta / Fresh flowers Tagetones, ocimene, myrcene

WCE, alt, 900-2000m (cultivated)

35 Thyme oil Thymus linnearis / Leaves and flowering tops

Thymol and carvacrol (up to 60%), cymene

W, alt, 2500-3800m

36 Valerian oil Valeriana jatamansii / Rhizomes

Bornyl acetate, isovalerate

WCE, alt, 1500-3300m

37 Vetiver oil Vetiveria zizanioides / Roots and leaves

Vetiverol, vitivone, terpenes

CE, alt, up to 300m

38 Wintergreen oil

Gaultheria fragrantissima / Leaves and twigs

Methyl salicylate (upto98%), gaultheriline

WCE, alt, 1200-2600m

39 Zanthoxylum oil

Zanthoxylum armatum / Dried fruits

Linalol (55-75%), methyl cinnamate, cineol

WCE, alt, 1100-2500m

Where, W: West; C: Central; E: East and alt: AltitudeSource: Lawless (1995); Press et al., 2000

Extraction method of essential oil:The basic methods of extraction of essential oil are distillation, enfleurage, maceration, solvent extraction, expression and supercritical fluid extraction. However, distillation has always been

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the most widely practiced methods of essential oil extraction. Distillation basically is the separation of components of a mixture of two or more liquids by virtue of differences in their vapor pressure.

Distillation process of essential oil:If essential oil is immiscible, steam distillation is employed. In this process, the distillate separates out as a layer of oil, distinct from a layer of water. But, if water and various components of essential oil mixture are miscible, it becomes necessary to use rectification and fractionation techniques.In order to isolate essential oil by the first process, steam is subjected into aromatic materials. Under the influence of steam, essential oil is freed from the glands of plant tissue. Both water and essential oil vaporized, condensed by an adjacent condenser and drained into a receptacle, where oil separates automatically above and below water, depending upon its density. Steam is continuously charged until all the essential oil is vaporized and the distillate formed in the condenser is essentially pure water.In the second process, involving rectification and fractionation, the mixture of essential oil produced by the foregoing method is isolated and purified. The process involves a gradual increase in the temperature of the mixture, where more volatile compounds in the oil distil first and less volatile compounds later. Several distillation processes may be necessary to attain the desired degree of purity in the distillate.

Storage of essential oil:Most essential oil deteriorate through oxidation and polymerization upon prolonged exposure to air and light. Therefore, producers should store essential oil in closed, completely filled containers and perfumers. In particular, essential oil should be stored in sealed bottles in dark and cool cellars. Without such precaution essences become less intense, grow darker and more viscous, develop a bleaching effect and eventually changes into a brown, odorless resin.

Mode of action of essential oil:Essential oil have three distinct modes of action with regard to how they interrelate with the human body; pharmacological, physiological and psychological. The pharmacological effect is concerned with the chemical changes that take place when an essential oil enters the bloodstream and reacts with the hormones and enzymes etc. The physiological mode with the way in which an essential oil affects the system of the body, whether they are sedated or stimulated etc. The psychological effect takes place when an essence is inhaled and an individual responds to its odor.

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Methods of application of essential oil:Essential oil can be used simply and effectively at home in a variety of ways, both for their scent and for their cosmetic and medicinal qualities. They can be added to the bath and used to make individual beauty preparations. They can also be employed in the treatment of minor first aid cases and to help prevent and relieve many common complaints as headaches, cold and coughs, period pains and aching muscles.

Constraints:It is seen that the rate of growth of aromatic plants in relation to their economic prospects is not satisfactory. It is due to the following constraints: Although diverse climate and soil exist in the country, the possibilities of raising large-scale plantations of aromatic plants on scientific lines has not been explored. Interspaces in the perennial plantations, vast stretches of forests and barren, waste and marginal lands are lying fallow, when they can be gainfully used to raise aromatic raw materials. Difficulties of processing in remote areas and transportation of the essential oil bearing plants to the nearest processing sites. Complex and restrictive process to obtain permits for collection, trade and export of aromatic plants and essential oils. Royalties for the aromatic plant products produced on private land and local taxes imposed by Village Development Committee and District Development Committee.

Future prospects:The demand for essential oil is increasing day by day with the advancement of education and prosperity in the country. Fragrance plays a vital role in securing consumer's acceptability in almost every product used. The following are the reasons for the scope of essential oil bearing plants: Essential oil is now a basic raw material for consumer products meant for mass consumption. The interest in aromatics for their therapeutic value is increasing due to the worldwide scare of the side effects of synthetics, also the revival of interest in herbs. Essential oil has the potential of being very safe insecticide. It has been found very effective and safe for the production of food grains. The cultivation and processing of aromatic plants is labor intensive and hence generates employment locally. The by products of aromatic plants can be used as a mulching material, fuel, cattle feed or ploughed back to soil to improve fertility.

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Private entrepreneurs can register the enterprises based on aromatic plants to process, sell and export of the products.

Conclusion and Recommendations:Nepal being rich in biodiversity has ample scope for sustainable and rational utilization of its natural resources as essential oil bearing aromatic plants. Its favorable climatic zones should be utilized for commercial cultivation of exotic as well as proven indigenous plants.The following are recommendations for the proper management of aromatic plants: It is very necessary to develop agro technology for the domestication of naturally occurring aromatic plants, basically those species exploited heavily. The collectors need to be trained regarding pre and post harvest technique to minimize wastage and losses. It is an opportune time to make organized efforts in the introduction of several new aromatic species of industrial utility and encourage their co-operative production and utilization in fast growing native industry as well as for expert. Product diversification and manufacture of finished formulations as health care herbal products and cosmetics should be encouraged.

References: Adhikary, S R.1989. Development of Essential Oils in Nepal. In:

Proceedings of the National Workshop on Chemical Investigation and Processing of Aromatic Plants, Sept. (11-18), 1989, Kathmandu.

Chaudhary, R P.1998. Biodiversity in Nepal: Status and Conservation. S. Devi Saharanpur (UP), India and Tec Press Book, Bangkok, Thailand.

DPR.1976. Medicinal Plants of Nepal. Department of Plant Resources, HMG/N, Kathmandu.

Farooqi, A A and B S Sreeramu. 2001. Cultivation of Medicinal and Aromatic Crops. Universities Press (India) Limited, India.

Lawless, J.1995. The Illustrated Encyclopedia of Essential Oils. Element Books Limited, UK.

Press, J R, K K Shrestha and D A Sutton. 2000. Annotated Checklist of the Flowering Plants of Nepal. The Natural History Museum, London.

Rawal, R B and J Pradhan. 1996. Essential Oil Bearing Plants and Their Commercial Processing in Nepal. In: Green Energy, Scientific Magazine, 2 (1): 43-50.

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