Essential oil

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An essential oil is a concentrated hydrophobic liquid containing volatile (easily evaporated at normal temperatures) chemical compounds from plants. Essential oils are also known as volatile oils, ethereal oils, aetherolea, or simply as the oil of the plant from which they were extracted, such as oil of clove. An essential oil is "essential" in the sense that it contains the "essence of" the plant's fragrance—the characteristic fragrance of the plant from which it is derived. [1] The term "essential" used here does not mean indispensable or usable by the human body, as with the terms essential amino acid or essential fatty acid, which are so called because they are nutritionally required by a given living organism. [2]

Contents

Essential oils are generally extracted by distillation, often by using steam. Other processes include expression, solvent extraction, sfumatura , absolute oil extraction, resin tapping, wax embedding, and cold pressing. They are used in perfumes, cosmetics, soaps and other products, for flavoring food and drink, and for adding scents to incense and household cleaning products. Essential oils should not be confused with perfume, fragrance, etc. as the latter usually include pure chemical components whereas essential oils are derived from plants.

Essential oils are often used for aromatherapy, a form of alternative medicine in which healing effects are ascribed to aromatic compounds. Aromatherapy may be useful to induce relaxation, but there is not sufficient evidence that essential oils can effectively treat any condition. [3] Improper use of essential oils may cause harm including allergic reactions and skin irritation, and children may be particularly susceptible to the toxic effects of improper use. [4] [5]

History

Essential oils have been used in folk medicine throughout history. The earliest recorded mention of the techniques and methods used to produce essential oils is believed to be that of Ibn al-Baitar (1188–1248), an Al-Andalusian (Muslim Spain) physician, pharmacist and chemist. [6]

Rather than refer to essential oils themselves, modern works typically discuss specific chemical compounds which the essential oils are composed of, such as referring to methyl salicylate rather than "oil of wintergreen". [7] [8]

Interest in essential oils has revived in recent decades with the popularity of aromatherapy, a branch of alternative medicine that uses essential oils and other aromatic compounds. Oils are volatilized, diluted in a carrier oil and used in massage, diffused in the air by a nebulizer, heated over a candle flame, or burned as incense.

Medical applications proposed by those who sell medicinal oils range from skin treatments to remedies for cancer and often are based solely on historical accounts of use of essential oils for these purposes. Claims for the efficacy of medical treatments, and treatment of cancers in particular, are now subject to regulation in most countries.

Production

Distillation

Most common essential oils such as lavender, peppermint, tea tree oil, patchouli, and eucalyptus are distilled. Raw plant material, consisting of the flowers, leaves, wood, bark, roots, seeds, or peel, is put into an alembic (distillation apparatus) over water. As the water is heated, the steam passes through the plant material, vaporizing the volatile compounds. The vapors flow through a coil, where they condense back to liquid, which is then collected in the receiving vessel.

Most oils are distilled in a single process. One exception is ylang-ylang ( Cananga odorata ) which is purified through a fractional distillation.

The recondensed water is referred to as a hydrosol, hydrolat, herbal distillate, or plant water essence, which may be sold as another fragrant product. Hydrosols include rose water, lavender water, lemon balm, clary sage, and orange blossom water. The use of herbal distillates in cosmetics is increasing.

Expression

Most citrus peel oils are expressed mechanically or cold-pressed (similar to olive oil extraction). [9] Due to the relatively large quantities of oil in citrus peel and low cost to grow and harvest the raw materials, citrus-fruit oils are cheaper than most other essential oils. Lemon or sweet orange oils are obtained as byproducts of the citrus industry.

Before the discovery of distillation, all essential oils were extracted by pressing. [10]

Solvent extraction

Most flowers contain too little volatile oil to undergo expression, but their chemical components are too delicate and easily denatured by the high heat used in steam distillation. Instead, a solvent such as hexane or supercritical carbon dioxide is used to extract the oils. [11] Extracts from hexane and other hydrophobic solvents are called concretes , which are a mixture of essential oil, waxes, resins, and other lipophilic (oil-soluble) plant material.

Although highly fragrant, concretes contain large quantities of non-fragrant waxes and resins. Often, another solvent, such as ethyl alcohol, is used to extract the fragrant oil from the concrete. The alcohol solution is chilled to −18 °C (0 °F) for more than 48 hours which causes the waxes and lipids to precipitate out. The precipitates are then filtered out and the ethanol is removed from the remaining solution by evaporation, vacuum purge, or both, leaving behind the absolute .

Supercritical carbon dioxide is used as a solvent in supercritical fluid extraction. This method can avoid petrochemical residues in the product and the loss of some "top notes" when steam distillation is used. It does not yield an absolute directly. The supercritical carbon dioxide will extract both the waxes and the essential oils that make up the concrete. Subsequent processing with liquid carbon dioxide, achieved in the same extractor by merely lowering the extraction temperature, will separate the waxes from the essential oils. This lower temperature process prevents the decomposition and denaturing of compounds. When the extraction is complete, the pressure is reduced to ambient and the carbon dioxide reverts to a gas, leaving no residue.

Florasols extraction

Florasol is another solvent used to obtain essential oils. It was originally developed as a refrigerant to replace Freon. Although Florasol is an "ozone-friendly" product, it has a high global warming potential (GWP; 100-yr GWP = 1430). [12] The European Union has banned its use, with a phase-out process that began in 2011, to be completed in 2017. [13] One advantage of Florasol is that the extraction of essential oils occurs at or below room temperature so degradation through high temperature extremes does not occur. The essential oils are mostly pure and contain little to no foreign substances.[ citation needed ]

Production quantities

Estimates of total production of essential oils are difficult to obtain. One estimate, compiled from data in 1989, 1990, and 1994 from various sources, gives the following total production, in tonnes, of essential oils for which more than 1,000 tonnes were produced. [14]

OilTonnes
Sweet orange 12,000
Mentha arvensis 4,800
Peppermint 3,200
Cedarwood 2,600
Lemon 2,300
Eucalyptus globulus 2,070
Litsea cubeba 2,000
Clove (leaf)2,000
Spearmint 1,300

Uses and cautions

Taken by mouth, many essential oils can be dangerous in high concentrations. Typical effects begin with a burning feeling, followed by salivation. [15] Different essential oils may have drastically different pharmacology. Some act as local anesthetic counterirritants and, thereby, exert an antitussive effect. [15] [16] Many essential oils, particularly tea tree oil, may cause contact dermatitis. [17] [18] [19] [20] Menthol and some others produce a feeling of cold followed by a sense of burning.

In Australia essential oils have been increasingly causing cases of poisoning, mostly of children. In the period 2014–2018 there were 4,412 poisoning incidents reported in New South Wales. [21]

Use in aromatherapy

Essential oils are used in aromatherapy as part of, for example, essential oil diffusers. Reed diffuser.jpg
Essential oils are used in aromatherapy as part of, for example, essential oil diffusers.

Aromatherapy is a form of alternative medicine in which healing effects are ascribed to the aromatic compounds in essential oils and other plant extracts. Aromatherapy may be useful to induce relaxation, but there is not sufficient evidence that essential oils can effectively treat any condition. [3] Scientific research indicates that essential oils cannot treat or cure any chronic disease or other illnesses. [22] Much of the research on the use of essential oils for health purposes has serious methodological errors. In a systemic review of 201 published studies on essential oils as alternative medicines, only 10 were found to be of acceptable methodological quality, and even these 10 were still weak in reference to scientific standards. [3] Use of essential oils may cause harm including allergic reactions and skin irritation; there has been at least one case of death. [4] As such, the use of essential oils as an alternative medicine should be approached with caution.

Use as pesticide

Research has shown that essential oils have potential as a natural pesticide. In case studies, certain oils have been shown to have a variety of deterring effects on pests, specifically insects and select arthropods. [23] These effects may include repelling, inhibiting digestion, stunting growth, [24] decreasing rate of reproduction, or death of pests that consume the oil. However, the molecules within the oils that cause these effects are normally non-toxic for mammals. These specific actions of the molecules allow for widespread use of these green pesticides without harmful effects to anything other than pests. [25] Essential oils that have been investigated include rose, lemon grass, lavender, thyme, peppermint, and eucalyptus. [26]

Although they may not be the perfect replacement for all synthetic pesticides, essential oils have prospects for crop or indoor plant protection, urban pest control, [27] and marketed insect repellents, such as bug spray. Certain essential oils have been shown in studies to be comparable, if not exceeding, in effectiveness to DEET, which is currently marketed as the most effective mosquito repellent. Although essential oils are effective as pesticides when first applied in uses such as mosquito repellent applied to the skin, it is only effective in the vapor stage. Since this stage is relatively short-lived, creams and polymer mixtures are used in order to elongate the vapor period of effective repellency. [23]

In any form, using essential oils as green pesticides rather than synthetic pesticides has ecological benefits such as decreased residual actions. [26] In addition, increased use of essential oils as pest control could have not only ecological, but economical benefits as the essential oil market diversifies [25] and popularity increases among organic farmers and environmentally conscious consumers. [24]

Use in food

In relation with their food applications, although these oils have been used throughout history as food preservatives, it was in the 20th century when EOs were considered as Generally Recognized as Safe (GRAS) by the Food and Drug Administration (FDA). [28]

GRAS substances according to the FDA [29]

Common nameBotanical name of plant source
Alfalfa Medicago sativa L.
Allspice Pimenta officinalis Lindl.
Almond, bitter (pure from prussic acid)Prunnus amygdalus Batsch, Prussun armeniaca L., or Prunnus persica (L.) Batsch.
Ambrette (seed)Hibiscus moschatus Moench.
Angelica root Angelica archangelica L.
Angelica seed Angelica archangelica L.
Angelica stem Angelica archangelica L.
Angostura (cusparia bark)Galipea officinalis Hancock, Angostura trifoliata
Anise Pimpinella anisum L.
Asafetida Ferula assa-foetida L. and related spp. of Ferula.
Balm (lemon balm)Melissa officinalis L.
Balsam of Peru Myroxylon pereirae Klotzsch.
Basil Ocimum basilicum L.
Bay leaves Laurus nobilis L.
Bay (myrcia oil) Pimenta racemosa (Mill.) J. W. Moore.
Bergamot (bergamot orange)Citrus aurantium L. subsp. bergamia Wright et Arn.
Bitter almond (free from prussic acid)Prunus amygdalus Batsch, Prunus armeniaca L., or Prunus persica (L.) Batsch.
Bois de rose Aniba rosaeodora Ducke.
Cacao Theobroma cacao L.
Camomile (chamomile) flowers, HungarianMatricaria chamomilla L.
Camomile (chamomile) flowers, Roman or EnglishAnthemis nobilis L.
Cananga Cananga odorata Hook. f. and Thoms.
Capsicum Capsicum frutescens L. and Capsicum annuum L.
Caraway Carum carvi L.
Cardamom seed (cardamon)Elettaria cardamomum Maton.
Carob bean Ceratonia siliqua L.
Carrot Daucus carota L.
Cascarilla bark Croton eluteria Benn.
Cassia bark, Chinese Cinnamomum cassia Blume.
Cassia bark, Padang or Batavia Cinnamomum burmanni Blume.
Cassia bark, Saigon Cinnamomum loureirii Nees.
Celery seed Apium graveolens L.
Cherry, wild, barkPrunus serotina Ehrh.
Chervil Anthriscus cerefolium (L.) Hoffm.
Chicory Cichorium intybus L.
Cinnamon bark, Ceylon Cinnamomum zeylanicum Nees.
Cinnamon bark, Chinese Cinnamomum cassia Blume.
Cinnamon bark, Saigon Cinnamomum loureirii Nees.
Cinnamon leaf, Ceylon Cinnamomum zeylanicum Nees.
Cinnamon leaf, ChineseCinnamomum cassia Blume.
Cinnamon leaf, SaigonCinnamomum loureirii Nees.
Citronella Cymbopogon nardus Rendle.
Citrus peels Citrus spp.
Clary (clary sage)Salvia sclarea L.
Clover Trifolium spp.
Coca (decocainized)Erythroxylum coca Lam. and other spp. of Erythroxylum.
Coffee Coffea spp.
Cola nut Cola acuminata Schott and Endl., and other spp. of Cola.
Coriander Coriandrum sativum L.
Cumin (cummin)Cuminum cyminum L.
Curacao orange peel (orange, bitter peel)Citrus aurantium L.
Cusparia barkGalipea officinalis Hancock.
Dandelion Taraxacum officinale Weber and T. laevigatum DC.
Dandelion rootTaraxacum officinale Weber and T. laevigatum DC.
Dog grass (quackgrass, triticum)Agropyron repens (L.) Beauv.
Elder flowersSambucus canadensis L. and S. nigra I.
Estragole (esdragol, esdragon, tarragon)Artemisia dracunculus L.
Estragon (tarragon) Artemisia dracunculus L.
Fennel, sweetFoeniculum vulgare Mill.
Fenugreek Trigonella foenum-graecum L.
Galanga (galangal)Alpinia officinarum Hance.
Geranium Pelargonium spp.
Geranium, East IndianCymbopogon martini Stapf.
Geranium, rosePelargonium graveolens L'Her.
GingerZingiber officinale Rosc.
GrapefruitCitrus paradisi Macf.
GuavaPsidium spp.
Hickory barkCarya spp.
Horehound (hoarhound)Marrubium vulgare L.
HopsHumulus lupulus L.
HorsemintMonarda punctata L.
Hyssop Hyssopus officinalis L.
Immortelle Helichrysum augustifolium DC.
Jasmine Jasminum officinale L. and other spp. of Jasminum.
Juniper (berries)Juniperus communis L.
Kola nut Cola acuminata Schott and Endl., and other spp. of Cola.
Laurel berriesLaurus nobilis L.
Laurel leavesLaurus spp.
Lavender Lavandula officinalis Chaix.
Lavender, spikeLavandula latifolia Vill.
Lavandin Hybrids between Lavandula officinalis Chaix and Lavandula latifolin Vill.
LemonCitrus limon (L.) Burm. f.
Lemon balm (see balm)Melissa officinalis L.
Lemon grass Cymbopogon citratus DC. and Cymbopogon lexuosus Stapf.
Lemon peelCitrus limon (L.) Burm. f.
Lime Citrus aurantifolia Swingle.
Linden flowersTilia spp.
Locust bean Ceratonia siliqua L,
Lupulin Humulus lupulus L.
Mace Myristica fragrans Houtt.
MandarinCitrus reticulata Blanco.
Marjoram, sweetMajorana hortensis Moench.
Yerba Mate Ilex paraguariensis St. Hil.
Melissa (see balm)
Menthol Mentha spp.
Menthyl acetate Do.
Molasses (extract)Saccarum officinarum L.
Mustard Brassica spp.
Naringin Citrus paradisi Macf.
Neroli, bigarade Citrus aurantium L.
Nutmeg Myristica fragrans Houtt.
OnionAllium cepa L.
Orange, bitter, flowersCitrus aurantium L.
Orange, bitter, peelDo.
Orange leafCitrus sinensis (L.) Osbeck.
Orange, sweetDo.
Orange, sweet, flowersDo.
Orange, sweet, peelDo.
Origanum Origanum spp.
Palmarosa Cymbopogon martini Stapf.
Paprika Capsicum annuum L.
Parsley Petroselinum crispum (Mill.) Mansf.
Pepper, black Piper nigrum L.
Pepper, whiteDo.
Peppermint Mentha piperita L.
Peruvian balsam Myroxylon pereirae Klotzsch.
Petitgrain Citrus aurantium L.
Petitgrain lemonCitrus limon (L.) Burm. f.
Petitgrain mandarin or tangerineCitrus reticulata Blanco.
Pimenta Pimenta officinalis Lindl.
Pimenta leaf Pimenta officinalis Lindl.
Pipsissewa leaves Chimaphila umbellata Nutt.
Pomegranate Punica granatum L.
Prickly ash bark Xanthoxylum (or Zanthoxylum) Americanum Mill. or Xanthoxylum clava-herculis L.
Rose absoluteRosa alba L., Rosa centifolia L., Rosa damascena Mill., Rosa gallica L., and vars. of these spp.
Rose (otto of roses, attar of roses)Do.
Rose budsDo.
Rose flowersDo.
Rose fruit (hips)Do.
Rose geraniumPelargonium graveolens L'Her.
Rose leavesRosa spp.
Rosemary Rosmarinus officinalis L.
Saffron Crocus sativus L.
Sage Salvia officinalis L.
Sage, GreekSalvia triloba L.
Sage, Spanish Salvia lavandulaefolia Vahl.
St. John's bread Ceratonia siliqua L.
Savory, summer Satureia hortensis L.
Savory, winterSatureia montana L.
Schinus molle Schinus molle L.
Sloe berries (blackthorn berries)Prunus spinosa L.
Spearmint Mentha spicata L.
Spike lavender Lavandula latifolia Vill.
Tamarind Tamarindus indica L.
Tangerine Citrus reticulata Blanco.
Tarragon Artemisia dracunculus L.
Tea Thea sinensis L.
Thyme Thymus vulgaris L. and Thymus zygis var. gracilis Boiss.
Thyme, whiteDo.
Thyme, wild or creepingThymus serpyllum L.
Triticum (see dog grass)Elymus repens
Tuberose Polianthes tuberosa L.
Turmeric Curcuma longa L.
Vanilla Vanilla planifolia Andr. or Vanilla tahitensis J. W. Moore.
Violet flowers Viola odorata L.
Violet leaves Viola odorata L.
Violet leaves absolute Viola odorata L.
Wild cherry bark Prunus serotina Ehrh.
Ylang-ylang Cananga odorata Hook. f. and Thoms.
Zedoary bark Curcuma zedoaria Rosc.

Dilution

Essential oils are usually lipophilic (literally: "oil-loving") compounds that are immiscible (not miscible) with water. They can be diluted in solvents like pure ethanol and polyethylene glycol. The most common way to safely dilute essential oils for topical use is in a carrier oil. This can be any vegetable oil readily available, the most popular for skin care being jojoba, coconut, wheat germ, olive and avocado.

Raw materials

Essential oils are derived from sections of plants. Some plants, like the bitter orange, are sources of several types of essential oil.

Bark
Berries
Flowers
Leaves
Peel
Resin
Rhizome
Roots
Seeds
Woods

Balsam of Peru

Balsam of Peru, an essential oil derived from the Myroxylon , is used in food and drink for flavoring, in perfumes and toiletries for fragrance, and in medicine and pharmaceutical items for healing properties.[ citation needed ] However, a number of national and international surveys have identified Balsam of Peru as being in the "top five" allergens most commonly causing patch test allergic reactions in people referred to dermatology clinics. [30] [31] [32]

Garlic oil

Garlic oil is an essential oil derived from garlic. [33]

Eucalyptus oil

Most eucalyptus oil on the market is produced from the leaves of Eucalyptus globulus. Steam-distilled eucalyptus oil is used throughout Asia, Africa, Latin America and South America as a primary cleaning/disinfecting agent added to soaped mop and countertop cleaning solutions; it also possesses insect and limited vermin control properties. [34] Note, however, there are hundreds of species of eucalyptus, and perhaps some dozens are used to various extents as sources of essential oils. Not only do the products of different species differ greatly in characteristics and effects, but also the products of the very same tree can vary grossly. [35]

Lavender oil

Lavender essential oil sold at a market in France. Marches des Producteurs de Pays 11 16 14.jpg
Lavender essential oil sold at a market in France.

Lavender oil has long been used in the production of perfume. [36] However, it can be estrogenic and antiandrogenic, causing problems for prepubescent boys and pregnant women, in particular. [37] Lavender essential oil is also used as an insect repellent. [38]

Rose oil

Rose oil is produced from the petals of Rosa damascena and Rosa centifolia . Steam-distilled rose oil is known as "rose otto", while the solvent extracted product is known as "rose absolute".

Dangers

The potential danger of an essential oil is sometimes relative to its level or grade of purity, and sometimes related to the toxicity of specific chemical components of the oil. Many essential oils are designed exclusively for their aroma-therapeutic quality; these essential oils generally should not be applied directly to the skin in their undiluted or "neat" form. Some can cause severe irritation, provoke an allergic reaction and, over time, prove hepatotoxic.

Some essential oils, including many of the citrus peel oils, are photosensitizers, increasing the skin's vulnerability to sunlight. [39]

Industrial users of essential oils should consult the safety data sheets to determine the hazards and handling requirements of particular oils. Even certain therapeutic-grade oils can pose potential threats to individuals with epilepsy or pregnant women.

Essential oil use in children can pose a danger when misused because of their thin skin and immature livers. This might cause them to be more susceptible to toxic effects than adults.  [5]

Flammability

The flash point of each essential oil is different. Many of the common essential oils, such as tea tree, lavender, and citrus oils, are classed as Class 3 Flammable Liquids, as they have a flash point of 50–60 °C.

Gynecomastia

Estrogenic and antiandrogenic activity have been reported by in vitro study of tea tree oil and lavender essential oils. Two published sets of case reports suggest that lavender oil may be implicated in some cases of gynecomastia, an abnormal breast tissue growth in prepubescent boys. [40] [41] The European Commission's Scientific Committee on Consumer Safety dismissed the claims against tea tree oil as implausible, but did not comment on lavender oil. [42] In 2018, a BBC report on a study stated that tea tree and lavender oils contain eight substances that when tested in tissue culture experiments, increasing the level of estrogen and decreasing the level of testosterone. Some of the substances are found in "at least 65 other essential oils". The study did not include animal or human testing. [43]

Handling

Exposure to essential oils may cause contact dermatitis. [18] [19] [20] Essential oils can be aggressive toward rubbers and plastics, so care must be taken in choosing the correct handling equipment. Glass syringes are often used, but have coarse volumetric graduations. Chemistry syringes are ideal, as they resist essential oils, are long enough to enter deep vessels, and have fine graduations, facilitating quality control. Unlike traditional pipettes, which have difficulty handling viscous fluids, the chemistry syringe, also known as a positive displacement pipette, has a seal and piston arrangement which slides inside the pipette, wiping the essential oil off the pipette wall.

Ingestion

Some essential oils qualify as GRAS flavoring agents for use in foods, beverages, and confectioneries according to strict good manufacturing practice and flavorist standards. [29] Pharmacopoeia standards for medicinal oils should be heeded. Some oils can be toxic to some domestic animals, cats in particular. [44] The internal use of essential oils can pose hazards to pregnant women, as some can be abortifacients in dose 0.5–10 mL, and thus should not be used during pregnancy.[ citation needed ]

Pesticide residues

There is some concern about pesticide residues in essential oils, particularly those used therapeutically. For this reason, many practitioners of aromatherapy buy organically produced oils. Not only are pesticides present in trace quantities, but also the oils themselves are used in tiny quantities and usually in high dilutions. Where there is a concern about pesticide residues in food essential oils, such as mint or orange oils, the proper criterion is not solely whether the material is organically produced, but whether it meets the government standards based on actual analysis of its pesticide content. [45]

Pregnancy

Certain essential oils are safe to use during pregnancy, but care must be taken when selecting quality and brand. [46] Some essential oils may contain impurities and additives that may be harmful to pregnant women. Sensitivity to certain smells may cause pregnant women to have adverse side effects with essential oil use, such as headache, vertigo, and nausea. Pregnant women often report an abnormal sensitivity to smells and taste, [47] and essential oils can cause irritation and nausea when ingested. Always consult a doctor before use.

Toxicology

The following table lists the LD50 or median lethal dose for common oils; this is the dose required to kill half the members of a tested animal population. LD50 is intended as a guideline only, and reported values can vary widely due to differences in tested species and testing conditions. [48]

Common NameOral LD50Dermal LD50Notes
Neem14 g/kg>2 g/kg
Lemon myrtle2.43 g/kg2.25 g/kg
Frankincense>5 g/kg>5 g/kgBoswellia carterii
Frankincense>2 g/kg>2 g/kgBoswellia sacra
Indian frankincense>2 g/kg>2 g/kgBoswellia serrata
Ylang-ylang>5 g/kg>5 g/kg
Cedarwood>5 g/kg>5 g/kg
Roman chamomile>5 g/kg>5 g/kg
White camphor>5 g/kg>5 g/kgCinnamomum camphora, extracted from leaves
Yellow camphor3.73 g/kg>5 g/kgCinnamomum camphora, extracted from bark
Hot oil3.80 g/kg>5 g/kgCinnamomum camphora, oil extracted from leaves
Cassia2.80 g/kg0.32 g/kg

Standardization of derived products

In 2002, ISO published ISO 4720 in which the botanical names of the relevant plants are standardized. [49] The rest of the standards with regards to this topic can be found in the section of ICS 71.100.60 [50]

See also

Related Research Articles

Patchouli species of plant

Patchouli, from Tamil paccuḷi, is a species of plant from the family Lamiaceae, commonly called the "mint" or "deadnettle" family. The plant grows as a bushy perennial herb, with erect stems reaching around 75 centimetres (2.5 ft) in height and bearing small, pale pink-white flowers. It is native to tropical regions of Asia, and is now extensively cultivated in China, Indonesia, Japan, Cambodia, Myanmar, India, Maldives, Malaysia, Mauritius, Seychelles, Madagascar, Taiwan, Pakistan, the Philippines, Thailand, Vietnam, South America and the Caribbean.

Lavender oil An essential oil obtained by distillation from the flower spikes of lavender flower

Lavender oil is an essential oil obtained by distillation from the flower spikes of certain species of lavender. There are over 400 types of lavender species worldwide with different scents and qualities. Two forms are distinguished, lavender flower oil, a colorless oil, insoluble in water, having a density of 0.885 g/mL; and lavender spike oil, a distillate from the herb Lavandula latifolia, having density 0.905 g/mL. Like all essential oils, it is not a pure compound; it is a complex mixture of phytochemicals, including linalool and linalyl acetate.

Tea tree oil essential oil derived from leaves

Tea tree oil, also known as melaleuca oil, is an essential oil with a fresh camphoraceous odor and a colour that ranges from pale yellow to nearly colourless and clear. It is derived from the leaves of the tea tree, Melaleuca alternifolia, native to southeast Queensland and the northeast coast of New South Wales, Australia. The oil comprises many constituent chemicals and its composition changes if it is exposed to air and oxidizes.

Absolute (perfumery) fragrance

Used in perfumery and aromatherapy, absolutes are similar to essential oils. They are concentrated, highly aromatic, oily mixtures extracted from plants. Whereas essential oils are produced by distillation, boiling or pressing, absolutes are produced through solvent extraction, or more traditionally, through enfleurage.

Neem oil Oil from the seeds of the genus Azadirachta

Neem oil is a vegetable oil pressed from the fruits and seeds of the neem, an evergreen tree which is indigenous to the Indian subcontinent and has been introduced to many other areas in the tropics. It is the most important of the commercially available products of neem for organic farming and medicines.

Steam distillation Steam distillation is a type of distillation (a separation or extraction process) for natural aromatic compounds from temperature-sensitive plants. It differs from hydrodistillation, where the plant can be immersed in water with or without steam.

Steam distillation is a separation process which consists in distilling water together with other volatile and non-volatile components. The steam from the boiling water carries the vapor of the volatiles to a condenser, where both are cooled and return to the liquid or solid state; while the non-volatile residues remain behind in the boiling container.

Insect repellent Substance which repels insects

An insect repellent is a substance applied to skin, clothing, or other surfaces which discourages insects from landing or climbing on that surface. Insect repellents help prevent and control the outbreak of insect-borne diseases such as malaria, Lyme disease, dengue fever, bubonic plague, river blindness and West Nile fever. Pest animals commonly serving as vectors for disease include insects such as flea, fly, and mosquito; and the arachnid tick.

<i>Eugenia uniflora</i> Species of flowering plant in the myrtle family Myrtaceae

Eugenia uniflora, the pitanga, Suriname cherry, Brazilian cherry, Cayenne cherry, cerisier carré, monkimonki kersie or ñangapirí, is a flowering plant in the family Myrtaceae, native to tropical South America’s east coast, ranging from Suriname, French Guiana to southern Brazil, as well as Uruguay and parts of Paraguay and Argentina. It is often used in gardens as a hedge or screen. The tree was introduced to Bermuda for ornamental purposes but is now out of control and listed as an invasive species. The tree has also been introduced to Florida.

Supercritical fluid extraction (SFE) is the process of separating one component (the extractant) from another (the matrix) using supercritical fluids as the extracting solvent. Extraction is usually from a solid matrix, but can also be from liquids. SFE can be used as a sample preparation step for analytical purposes, or on a larger scale to either strip unwanted material from a product (e.g. decaffeination) or collect a desired product (e.g. essential oils). These essential oils can include limonene and other straight solvents. Carbon dioxide (CO2) is the most used supercritical fluid, sometimes modified by co-solvents such as ethanol or methanol. Extraction conditions for supercritical carbon dioxide are above the critical temperature of 31 °C and critical pressure of 74 bar. Addition of modifiers may slightly alter this. The discussion below will mainly refer to extraction with CO2, except where specified.

Rose oil essential oil

Rose oil is the essential oil extracted from the petals of various types of rose. Rose ottos are extracted through steam distillation, while rose absolutes are obtained through solvent extraction, the absolute being used more commonly in perfumery. Even with their high price and the advent of organic synthesis, rose oils are still perhaps the most widely used essential oil in perfumery.

Eucalyptol chemical compound

Eucalyptol is a natural organic compound that is a colorless liquid. It is a cyclic ether and a monoterpenoid.

Orange oil Essential oil of orange fruit

Orange oil is an essential oil produced by cells within the rind of an orange fruit. In contrast to most essential oils, it is extracted as a by-product of orange juice production by centrifugation, producing a cold-pressed oil. It is composed of mostly d-limonene, and is often used in place of pure d-limonene. D-limonene can be extracted from the oil by distillation.

Peppermint extract is an herbal extract of peppermint made from the essential oils of peppermint leaves. Peppermint is a hybrid of water mint and spearmint and was indigenous to Europe and the Middle East before it became common in other regions, such as North America and Asia.

Verbenone chemical compound

Verbenone is a natural organic compound classified as a terpene that is found naturally in a variety of plants. The chemical has a pleasant characteristic odor. Besides being a natural constituent of plants, it and its analogs are insect pheromones. In particular, verbenone when formulated in a long-lasting matrix has an important role in the control of bark beetles such as the mountain pine beetle and the Southern pine bark beetle.

Eucalyptus oil is the generic name for distilled oil from the leaf of Eucalyptus, a genus of the plant family Myrtaceae native to Australia and cultivated worldwide. Eucalyptus oil has a history of wide application, as a pharmaceutical, antiseptic, repellent, flavouring, fragrance and industrial uses. The leaves of selected Eucalyptus species are steam distilled to extract eucalyptus oil.

Fragrance extraction the process of obtaining fragrant oils and compounds from raw materials

Fragrance extraction refers to the separation process of aromatic compounds from raw materials, using methods such as distillation, solvent extraction, expression, sieving, or enfleurage. The results of the extracts are either essential oils, absolutes, concretes, or butters, depending on the amount of waxes in the extracted product.

Herbal distillate Herbal distillate

Herbal distillates, also known as floral waters, hydrosols, hydrolates, herbal waters, and essential waters, are aqueous products of hydrodistillation. They are colloidal suspensions of essential oils as well as water-soluble components obtained by steam distillation or hydrodistillation from plants/herbs. These herbal distillates have uses as flavorings and cosmetics. Popular herbal distillates for skincare include rose water, orange flower water, and witch hazel. Rosemary, oregano and thyme are very popular hydrosols for food production.

Aromatherapy Usage of aromatic materials for improving well-being

Aromatherapy is based on the usage of aromatic materials, including essential oils, and other aroma compounds, with claims for improving psychological or physical well-being. It is offered as a complementary therapy or as a form of alternative medicine, the first meaning alongside standard treatments, the second instead of conventional, evidence-based treatments.

Bergamot essential oil Cold-pressed essential oil

Bergamot essential oil is a cold-pressed essential oil produced by cells inside the rind of a bergamot orange fruit. It is a common flavoring and top note in perfumes. The scent of bergamot essential oil is similar to a sweet light orange peel oil with a floral note.

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Further reading