**4. Factors affecting chemical composition of volatile oils**

The fragrance and chemical composition of the oils can vary according to different factors as the geo-climatic location and growing conditions (soil type, climate, altitude, and amount of water available), season, and time of day when harvesting is done. Therefore, these factors influence the biochemical synthesis of the oils in a plant, so that the same species of the plant make the same volatile oil but maybe of different chemical compounds, which will affect their therapeutic activities. These different chemical compositions led to different chemotypes. Chemotype is in general a different population of the same species of plant which produces many chemical profiles for a particular class of secondary metabolites. Examples of some chemotypes are shown in **Table 1** [24–27].

called the mint family. It is one of most important plant families in the plant kingdom. This family is rich in essential oils, especially menthol thyme, Rosemary, and Oregano. Apiaceae or Umbelliferae is a family of mostly aromatic flowering pla nts, which contains economically important plants as caraway, coriander, cumin, and fennel [28–31]. Volatile oils contribute in a lot of industries as food products, drinks, perfumes, pharmaceuticals, and cosmetics [32–34]. The production and consumption of essential oils increase rapidly all over the world [35]. Regardless of the high costs because of the large amounts of plant material needed, volatile oil production has been increasing. The expected world production of the oils ranges from 40,000 to 60,000 tons/year and represents a market of approximately 700 million US\$ [36, 37]. Examples of some classes of essential oils their medical uses

**Lactones** Nepetalactone, bergaptene Antimicrobial antiviral, antipyretic,

**Example Bioactivities References**

Mucolytic, cell regenerating, sedative, antiviral, neurotoxic, analgesic, spasmolytic

Antiviral, antimicrobial, tonic, vasodilators, hypotensive, calming,

Antimicrobial, spasmolytic, immune

Antimicrobial, antiseptic, tonifying,

sedative, hypotensive, analgesic

Stimulant, antiviral, antitumor, decongestant, antibacterial, hepatoprotective

Spasmolytic, sedative, antifungal,

Anti-inflammatory, expectorant,

anti-inflammatory

stimulant

antipyretic, sedative

stimulating

spasmolytic

[38–40]

[26, 41]

[26, 40]

[26, 40]

[26, 40]

[26, 40]

[26, 40]

[26, 40]

and structures are illustrated in (**Table 2**), (**Figures 1** and **2**) [26, 38–41].

Many plant essential oils are used as medicine for hundreds of years and have demonstrated several health benefits, including effects on infectious, chronic, and acute diseases. The medical preparations made with plant essential oils as well as their single constituents applied in the therapy of human infectious diseases are well documented. However, the selection of suitable safe oil and the determination of the best efficient dose should be taken into consideration to avoid any side effects when they are applied [41]. The action of volatile oils begins by entering the human body through three possible ways including direct absorption through inhalation,

**6. Therapeutic benefits of essential oils**

**Class of compounds**

**Table 2.**

**111**

**Ketones** Carvone, menthone, pulegone, fenchone, camphor

*Aromatherapy as Complementary Medicine DOI: http://dx.doi.org/10.5772/intechopen.92021*

**Phenols** Thymol, eugenol, carvacrol, chavicol

**Alcohols** Linalool, menthol, borneol,

geraniol

**Hydrocarbons** Limonene, myrcene, pinene,

phellandrene

**Esters** Linalyl acetate, geraniol acetate,

**Oxides** Bisabolone oxide, linalool oxide, sclareol oxide

*Different classes of volatile oils and their biological activities.*

cuminaldehyde, citronellal, cinnamaldehyde, benzaldehyde

santalol, nerol, citronellol,

sabinene, cymene, myrcene,

eugenol acetate, bornyl acetate

**Aldehydes** Citral, myrtenal,

ingestion, or diffusion through the skin tissue.
