**2. Properties and characterization**

The characterization of an essential oil starts with the designation of the vegetable source, i.e., plant, from which it was isolated and the part of the used plant (flowers, leaves, fruits, rhizomes, roots, etc.). It is important to supply, together with the vulgar (vernacular) name of the plant, for example, rosemary, its botanical name (taxonomic identification), which consists of the names of the genus and the species, in this case, *Rosmarinus* (genus) *officinalis* (species) of the Labiatae family and, if the subspecies exists or the variety of the plant, it is important to add it.

It is also necessary to specify, if there is, the chemist of the plant, which receives often its name for the compound majority or distinctive, present in the essential oil. Botanical identification, through the scientific name of the plant, it allows to avoid confusion.

For example, under the vulgar name of "chamomile" they can figure different species, with oils essential composition and properties well different, i.e., German chamomile is Matricaria recutita (*Matricaria chamomilla*) and the Roman chamomile is *Anthemis nobilis*; both belong to the family Asteraceae (Compositae) and both are commonly called "chamomile." Along with identification botany, the provenance of the plant, that is, where it was cultivated (country, region) and what was the extraction method of its essential oil (steam drag or hydrodilatation).

Many factors affect the composition and yield of essential oil in the plant. Among the main ones are: geoclimatic localization, type of soil, stage of development of the plant (e.g., before, during or after flowering) and even the time of day when it is harvested, among others. Geoclimatic factors and soil type can give rise to different chemotypes of the plant, from which essential oils with chemical composition, sensory properties and different biological activity are distilled. For example, in thyme, *Thymus vulgaris* (Fam. Labiatae), at least four chemists are distinguished, according to their major compounds in the essential oil: (I) thymol and p-cymene; (II) carvacrol, timol and borneol; (III) linalool, terpinen-4-ol and linalyl acetate and (IV) geraniol and geranyl acetate. Each oil isolated from these chemotypes, smells different and has different biological properties.

While thymus chemotypes I and II have a strong antibacterial activity, they are irritant, chemotypes III and IV are not and have a moderate antibacterial activity. Thyme chemotype III oil has a sedative effect due to the presence of linalool, monoterpene alcohol, and its acetate [15].

Another example, is the essential oils of geranium plants (*Pelargonium graveolens*), cultivated in the Reunion Islands (Indian Ocean, northern Madagascar) and in China. In the international market the first essential oil is known as "Bourbon" and the second is called "Chinese geranium oil"; its chemical compositions vary widely [15], which can be seen in **Table 1**.

**71**

*Essential Oils in the Development of New Medicinal Products*

the time when the collection of *Salvia officinalis* is done.

**3. Essential oils used against bacteria and microbes**

bacteria, obtained from these natural products [19].

antimicrobial and anticancer properties.

Another important parameter is the time of harvest of the plant; from this depend both the yield and the composition of the extracted oil [16]. For example, sage essential oil (*Salvia officinalis*, Fam. Labiatae) contains a neurotoxic monoterpene ketone, α-thujone [15], in different amounts, depending on the time when the plant is harvested. The content of the ketone varies as follows: it is high, when the plant is harvested after flowering, and it is low before its flowering. This is precisely

*Comparison of essential oils, according to their major compounds isolated from geraniums cultivated in China* 

**Compounds Geranium (China), % Geranium (reunion), %**

Citronellol 40 22 Citronellyl formate 11 8 Geraniol 6 17 Geranyl formate 2 7.5 Linalool 4 13

The jasmine flowers collected in the morning hours contain in their oil a preferred combination of linalool, benzyl alcohol, cis-jasmone and indole, but when the flowers are collected in the afternoon hours, their oils have high levels of benzyl benzoate, eugenol and methyl salicylate; the last two introduce some unpleasant and undesirable scent notes, which can generate a rejection in the perfume industry or in aromatherapy. For ylang-ylang (*Cananga odorata*, Fam. Anonácea), the state of its flowers, i.e., fresh vs. wilted, or ripe, yellow vs. green and underdeveloped, notably affects the composition of the oil obtained: the Extra quality of the oil is reached, among other factors, when the yellow flowers are exclusively distilled, completely developed, freshly collected during the first hours of the morning [17].

It is a fact that many of the bacterial infections have increased even after the discovery of many antibiotics, among other factors due to the appearance of strains resistant to antibiotics and the increase of the population with less immunity. This being one of the main causes of deaths due to infectious diseases caused by bacteria [18]. Additionally, the effects of toxicity due to side effects restrict the prolonged use of high concentrations of available antibacterial drugs. In this way it is evident the need to explore new molecules and alternative treatments against pathogenic

Many plant species contain molecules with antimicrobial properties. It has been shown that especially plant OEs exhibit broad-spectrum inhibitory activities against various bacterial pathogens [20]. In the case of the family of grasses, Poaceae, which includes the producer of lemongrass oil (of *Cymbopogon citratus*), citronella oil (of *C. nardus*) and palmarosa oils (*C. martinii*). The medicinally active components of these EOs are citral, geraniol and geranyl acetate. They have demonstrated

In the case of citrus oils that constitute limonene and linalool are derived from the fruit peel of the plants belonging to the Rutaceae family, it has been shown that these components exhibit antimicrobial potential. In the case of the plants *Pelargonium graveolens* and *Santalum* spp. of the family Geraniaceae and Santalaceae, respectively, it has been determined that they possess two important

oils, namely, geranium oil and sandalwood, with similar properties [21].

*DOI: http://dx.doi.org/10.5772/intechopen.86572*

**Table 1.**

*and Reunion Islands.*

*Essential Oils in the Development of New Medicinal Products DOI: http://dx.doi.org/10.5772/intechopen.86572*


**Table 1.**

*Essential Oils - Oils of Nature*

main components [11].

others, of the EOs [14].

confusion.

health, agriculture, cosmetics and food.

**2. Properties and characterization**

this way the characteristics of the EOs is the result of a synergic effect between the

Currently there is a worldwide effort to study and understand the phytotherapeutic, antimicrobial, antimutagenic, anticancer, antioxidant properties, among

The characterization of an essential oil starts with the designation of the vegetable source, i.e., plant, from which it was isolated and the part of the used plant (flowers, leaves, fruits, rhizomes, roots, etc.). It is important to supply, together with the vulgar (vernacular) name of the plant, for example, rosemary, its botanical name (taxonomic identification), which consists of the names of the genus and the species, in this case, *Rosmarinus* (genus) *officinalis* (species) of the Labiatae family and, if the subspecies exists or the variety of the plant, it is important to add it.

It is also necessary to specify, if there is, the chemist of the plant, which receives often its name for the compound majority or distinctive, present in the essential oil. Botanical identification, through the scientific name of the plant, it allows to avoid

For example, under the vulgar name of "chamomile" they can figure different species, with oils essential composition and properties well different, i.e., German chamomile is Matricaria recutita (*Matricaria chamomilla*) and the Roman chamomile is *Anthemis nobilis*; both belong to the family Asteraceae (Compositae) and both are commonly called "chamomile." Along with identification botany, the provenance of the plant, that is, where it was cultivated (country, region) and what was the extraction method of its essential oil (steam drag or hydrodilatation). Many factors affect the composition and yield of essential oil in the plant. Among the main ones are: geoclimatic localization, type of soil, stage of development of the plant (e.g., before, during or after flowering) and even the time of day when it is harvested, among others. Geoclimatic factors and soil type can give rise to different chemotypes of the plant, from which essential oils with chemical composition, sensory properties and different biological activity are distilled. For example, in thyme, *Thymus vulgaris* (Fam. Labiatae), at least four chemists are distinguished, according to their major compounds in the essential oil: (I) thymol and p-cymene; (II) carvacrol, timol and borneol; (III) linalool, terpinen-4-ol and linalyl acetate and (IV) geraniol and geranyl acetate. Each oil isolated from these

chemotypes, smells different and has different biological properties.

monoterpene alcohol, and its acetate [15].

widely [15], which can be seen in **Table 1**.

While thymus chemotypes I and II have a strong antibacterial activity, they are irritant, chemotypes III and IV are not and have a moderate antibacterial activity. Thyme chemotype III oil has a sedative effect due to the presence of linalool,

Another example, is the essential oils of geranium plants (*Pelargonium graveolens*), cultivated in the Reunion Islands (Indian Ocean, northern Madagascar) and in China. In the international market the first essential oil is known as "Bourbon" and the second is called "Chinese geranium oil"; its chemical compositions vary

We can find from natural products, as well as from their derivatives, new therapeutic sources for various treatments of diseases [12, 13]. Humanity has used natural products since antiquity for the treatment of various diseases, so it is not surprising that this knowledge is sought from a new scientific perspective. Within the natural products we can find the EOs, which have diverse applications mainly in

**70**

*Comparison of essential oils, according to their major compounds isolated from geraniums cultivated in China and Reunion Islands.*

Another important parameter is the time of harvest of the plant; from this depend both the yield and the composition of the extracted oil [16]. For example, sage essential oil (*Salvia officinalis*, Fam. Labiatae) contains a neurotoxic monoterpene ketone, α-thujone [15], in different amounts, depending on the time when the plant is harvested. The content of the ketone varies as follows: it is high, when the plant is harvested after flowering, and it is low before its flowering. This is precisely the time when the collection of *Salvia officinalis* is done.

The jasmine flowers collected in the morning hours contain in their oil a preferred combination of linalool, benzyl alcohol, cis-jasmone and indole, but when the flowers are collected in the afternoon hours, their oils have high levels of benzyl benzoate, eugenol and methyl salicylate; the last two introduce some unpleasant and undesirable scent notes, which can generate a rejection in the perfume industry or in aromatherapy. For ylang-ylang (*Cananga odorata*, Fam. Anonácea), the state of its flowers, i.e., fresh vs. wilted, or ripe, yellow vs. green and underdeveloped, notably affects the composition of the oil obtained: the Extra quality of the oil is reached, among other factors, when the yellow flowers are exclusively distilled, completely developed, freshly collected during the first hours of the morning [17].
