**2. Sources and isolation of essential oils**

Essential oils were extracted from different aromatic plants. These plants are distributed in the tropical countries and Mediterranean. These plants got importance because local people use them for the treatment of diseases. The essential oil is produced in every part of the plant including the leaves, seeds, buds, stem, flowers, leaves etc as shown in **Figure 1**. Essential oil is accumulated from the epidermic cell, cavities, secretary cells, and channels [10]. The odor that is produced in plants is because of essential oils. The essential oils were extracted from the dried, fresh, or partially dehydrated materials of plant. The extraction rate depends upon the diffusion via plant tissues that directly involve the surface from which the essential oil was removed by different processes. The extraction of essential oil depends upon the stability of the essential oil. The two most important method that are used for the extraction of essential oil was used are steam distillation method and the hydro distillation process as shown in **Figure 2**. These are the most suitable and effective techniques for the extraction processes [11]. Some other methods were also used for extraction but they are not too much suitable for this process these are the microwave or liquid carbon dioxide, high- or low-pressure distillation with the help hot water or steam water (**Figures 1** and **2**) [12].

The essential oil extracted from the steam distillation method is mostly used in pharmacological activities and food items, while the essential oil that are used in the fragrance industry or perfume industry are extracted from the lipophilic solvents and sometime with the supercritical carbon dioxide going more attractive [13]. The quality of the essential oil depended on the basis of the age of plants, parts that are used for extraction, vegetative cycle stage, effect of climate, etc. The chromatographic and the spectroscopic techniques fully changed the chemical analysis of the essential oils. The chemical composition of the essential oils was studied with the help of IR-spectroscopy, UV-Vis spectroscopy, gas chromatography, NMR

**39**

**Figure 2.**

**Figure 1.**

the plant material [16].

spectroscopy [14]. The enhanced demand for the essential oil in various fields of life provoked us to access the reliable methods for the essential oil analysis, and the techniques used are the GC-MS and GC analyses [15]. The characterization of the essential oil was carried out by using the gas chromatography. The compounds that are present in the essential oil was confirmed by using the GC and GC-MS analysis [16]. The storage and handling of the essential oil also affect its yield and quality, ad essential oil was deposited in the oil glands that are present in the organization of

*Hydrodistillation apparatus used for the extraction of essential oils.*

*Biological Importance of Essential Oils*

*DOI: http://dx.doi.org/10.5772/intechopen.87198*

*Plants and their parts used for the isolation of essential oils.*

*Biological Importance of Essential Oils DOI: http://dx.doi.org/10.5772/intechopen.87198*

*Essential Oils - Oils of Nature*

types [9].

and as medicines [5]. Previously, essential oils have been used for the treatment of various sorts of infectious diseases in the whole world. Now, in this era, the importance of essential oils is increasing day by day, because they are mostly used in the beverage and food industries, cosmetics and fragrance industries for making

Various essential oils have been used for the insecticidal activities against the different pests, but in detail, studies showed that they do not show the repellence, avicidal, phytochemistry, antifungal, and oviposition. The essential oils do not show the abovementioned characteristics, but there is still urgent need to work on this side of research and study the in vivo and in vitro studies to control the pests, and most of the oils have shown good antioxidant activities [7]. Essential oils that showed good antioxidant activates and acts as the defensive role for the unsaturation of lipids in the tissue of the animal and they also act as hepatoprotective negotiators in mammals. The antioxidant substances are most important for human being because of the oxygen which is a toxic element and has the ability to change the metabolic activities into the most reactive form of oxygen just like the super oxide, hydrogen peroxide, hydroxyl free radicals, and the singlet oxygen which are collectively called as active oxygen [8]. Essential oils are best known for their action as the antispasmodic, antiviral negotiators, antimicrobial, and carminative, and the essential oil composition is variable; they also show different sorts of activities and mostly depend upon the chemo

Essential oils were extracted from different aromatic plants. These plants are distributed in the tropical countries and Mediterranean. These plants got importance because local people use them for the treatment of diseases. The essential oil is produced in every part of the plant including the leaves, seeds, buds, stem, flowers, leaves etc as shown in **Figure 1**. Essential oil is accumulated from the epidermic cell, cavities, secretary cells, and channels [10]. The odor that is produced in plants is because of essential oils. The essential oils were extracted from the dried, fresh, or partially dehydrated materials of plant. The extraction rate depends upon the diffusion via plant tissues that directly involve the surface from which the essential oil was removed by different processes. The extraction of essential oil depends upon the stability of the essential oil. The two most important method that are used for the extraction of essential oil was used are steam distillation method and the hydro distillation process as shown in **Figure 2**. These are the most suitable and effective techniques for the extraction processes [11]. Some other methods were also used for extraction but they are not too much suitable for this process these are the microwave or liquid carbon dioxide, high- or low-pressure distillation with the help hot water or steam water

The essential oil extracted from the steam distillation method is mostly used in pharmacological activities and food items, while the essential oil that are used in the fragrance industry or perfume industry are extracted from the lipophilic solvents and sometime with the supercritical carbon dioxide going more attractive [13]. The quality of the essential oil depended on the basis of the age of plants, parts that are used for extraction, vegetative cycle stage, effect of climate, etc. The chromatographic and the spectroscopic techniques fully changed the chemical analysis of the essential oils. The chemical composition of the essential oils was studied with the help of IR-spectroscopy, UV-Vis spectroscopy, gas chromatography, NMR

valuable perfumes, and with lot of biological activities [6].

**2. Sources and isolation of essential oils**

**38**

(**Figures 1** and **2**) [12].

#### **Figure 1.** *Plants and their parts used for the isolation of essential oils.*

**Figure 2.** *Hydrodistillation apparatus used for the extraction of essential oils.*

spectroscopy [14]. The enhanced demand for the essential oil in various fields of life provoked us to access the reliable methods for the essential oil analysis, and the techniques used are the GC-MS and GC analyses [15]. The characterization of the essential oil was carried out by using the gas chromatography. The compounds that are present in the essential oil was confirmed by using the GC and GC-MS analysis [16]. The storage and handling of the essential oil also affect its yield and quality, ad essential oil was deposited in the oil glands that are present in the organization of the plant material [16].
