*2.3.2 Analysis of essential oils*

As the consumption of EOs is growing up annually, their world production by different companies to satisfy the market demand has been increasing every year. The quality control of produced EOs has become then necessary to ensure the

#### **Figure 11.**

*Schematic representation of the solvent-free microwave extraction apparatus [63].*

**85**

activities.

*2.4.1 Antioxidant activity*

23.4%, respectively [87].

*2.4.2 Anticancer activity*

*Terpenoids as Important Bioactive Constituents of Essential Oils DOI: http://dx.doi.org/10.5772/10.5772/intechopen.91426*

density, the optical rotation, the refractive index, etc.

dimensional gas chromatography (MDGC) [68–78].

**2.4 Bioactivities and toxicity of essential oils**

genuineness of the product, the shelf life, and the storage conditions [67]. The EO composition can sometimes be falsified by adding cheaper oils; it is often necessary to characterize small differences between oils that correspond to variation in geographic or genetic origin of the plant material. EOs analysis can be summarized in few points: the qualitative composition, the quantitative determination (major and/ or minor constituents), and the detection of alteration of true EOs. With regard to the quality aspect of the EO, the identity and the purity are always investigated. Their physical properties are commonly assessed by specific gravity, the relative

Most of the methods applied in the analysis of EOs rely on chromatographic procedures, which enable component separation and identification. These include gas chromatography–mass spectrometry (GC–MS), liquid chromatography-mass spectrometry (LC–MS), gas chromatography-Fourier transform infrared spectrometry (GC-FT-IR), gas chromatography-Fourier transform infrared spectrometrymass spectrometry (GC-FT-IR-MS), gas chromatography-atomic emission detector (GC-AED), gas chromatography-isotope ratio mass spectrometry (GC-IR-MS), on-line coupled liquid chromatography-gas chromatography (LC-GC), and multi-

A considerable large number of studies on EOs to evaluate their pharmacological properties and toxicity in order to find possible alternative medicine have become active in recent years [79]. EOs are known to exhibit a large range of biological

It is one of the most intensively studied properties of EOs. This could be explained by the damages of various biological substances by oxidation which subsequently causes many degenerative and/or metabolic diseases such as cancer, diabetes, arthritis, inflammation, and Parkinson's and Alzheimer's disease just to name a few [80–84]. EOs are known as rich sources of potential antioxidants that can be investigated to prevent oxidative damage [85]. Antioxidants comprise substances that, in low concentrations, significantly delay or inhibit the oxidation of the substrate [86]. Volatile compounds in EO, beside their protective antioxidant activity, can also act as prooxidant, by affecting the cellular redox status and damage cellular biomolecules, in the first instance proteins and DNA [15]. All these must be taken into account when antioxidant properties of EOs are considered. Although phenolic compounds are recognized as being responsible for the antioxidant ability, recent studies showed that volatile components could also individually and/or in mixture (essential oil) contribute to the whole antioxidant ability. EO of lemon balm (*Melissa officinalis* L.) was reported to exhibit the highest antioxidant activity than BHT. Its GC–MS analysis showed that the main compounds were citronellal, neral, and geranial with a percentage yield of 13.7, 16.5, and

Cancer is a worldwide public health concern with 18.1 million people been diagnosed with the disease annually. It is the second largest single leading cause of death claiming in excess of 9.6 million lives in the world in 2018, with approximately 70% of deaths occurring in low- and middle-income countries [88]. Current

**Figure 12.** *Schematic representation of the microwave hydrodiffusion and gravity [65].*

#### *Terpenoids as Important Bioactive Constituents of Essential Oils DOI: http://dx.doi.org/10.5772/10.5772/intechopen.91426*

*Essential Oils - Bioactive Compounds, New Perspectives and Applications*

consumption (**Figure 11**) [62].

*2.3.2 Analysis of essential oils*

*2.3.1.2.7 Microwave hydrodiffusion and gravity*

method increases the EO yield, ameliorate the EO composition, eliminate the waste of water treatment, and also contributes to limited time, and lower an energy

Microwave hydrodiffusion and gravity (MHG) is a new green extraction technique of EOs developed by Vian and collaborators in 2008. This green extraction technique is an original "upside down" microwave alembic combining microwave heating and earth gravity at atmospheric pressure [65]. MHG has become not only an economic and efficient but also an environmental- and eco-friendly, not require

As the consumption of EOs is growing up annually, their world production by different companies to satisfy the market demand has been increasing every year. The quality control of produced EOs has become then necessary to ensure the

water or solvent and as it does require less energy (**Figure 12**) [65, 66].

*Schematic representation of the solvent-free microwave extraction apparatus [63].*

*Schematic representation of the microwave hydrodiffusion and gravity [65].*

**84**

**Figure 12.**

**Figure 11.**

genuineness of the product, the shelf life, and the storage conditions [67]. The EO composition can sometimes be falsified by adding cheaper oils; it is often necessary to characterize small differences between oils that correspond to variation in geographic or genetic origin of the plant material. EOs analysis can be summarized in few points: the qualitative composition, the quantitative determination (major and/ or minor constituents), and the detection of alteration of true EOs. With regard to the quality aspect of the EO, the identity and the purity are always investigated. Their physical properties are commonly assessed by specific gravity, the relative density, the optical rotation, the refractive index, etc.

Most of the methods applied in the analysis of EOs rely on chromatographic procedures, which enable component separation and identification. These include gas chromatography–mass spectrometry (GC–MS), liquid chromatography-mass spectrometry (LC–MS), gas chromatography-Fourier transform infrared spectrometry (GC-FT-IR), gas chromatography-Fourier transform infrared spectrometrymass spectrometry (GC-FT-IR-MS), gas chromatography-atomic emission detector (GC-AED), gas chromatography-isotope ratio mass spectrometry (GC-IR-MS), on-line coupled liquid chromatography-gas chromatography (LC-GC), and multidimensional gas chromatography (MDGC) [68–78].

## **2.4 Bioactivities and toxicity of essential oils**

A considerable large number of studies on EOs to evaluate their pharmacological properties and toxicity in order to find possible alternative medicine have become active in recent years [79]. EOs are known to exhibit a large range of biological activities.

#### *2.4.1 Antioxidant activity*

It is one of the most intensively studied properties of EOs. This could be explained by the damages of various biological substances by oxidation which subsequently causes many degenerative and/or metabolic diseases such as cancer, diabetes, arthritis, inflammation, and Parkinson's and Alzheimer's disease just to name a few [80–84]. EOs are known as rich sources of potential antioxidants that can be investigated to prevent oxidative damage [85]. Antioxidants comprise substances that, in low concentrations, significantly delay or inhibit the oxidation of the substrate [86]. Volatile compounds in EO, beside their protective antioxidant activity, can also act as prooxidant, by affecting the cellular redox status and damage cellular biomolecules, in the first instance proteins and DNA [15]. All these must be taken into account when antioxidant properties of EOs are considered.

Although phenolic compounds are recognized as being responsible for the antioxidant ability, recent studies showed that volatile components could also individually and/or in mixture (essential oil) contribute to the whole antioxidant ability. EO of lemon balm (*Melissa officinalis* L.) was reported to exhibit the highest antioxidant activity than BHT. Its GC–MS analysis showed that the main compounds were citronellal, neral, and geranial with a percentage yield of 13.7, 16.5, and 23.4%, respectively [87].

#### *2.4.2 Anticancer activity*

Cancer is a worldwide public health concern with 18.1 million people been diagnosed with the disease annually. It is the second largest single leading cause of death claiming in excess of 9.6 million lives in the world in 2018, with approximately 70% of deaths occurring in low- and middle-income countries [88]. Current valuable drugs used in the treatment include vinblastine, vincristine, camptothecin, and Taxol [89]. Many studies pointed out the anticancer properties of plants. Over 500 research papers are published on the anticancer activity of EOs [90–93], even though, till date, there are no scientific studies showing that aromatherapy can cure or prevent cancer. Most promising research results obtained from in vitro studies revealed that EOs were found to affect cancer cell lines in petri dishes. EOs are well known for their anti-inflammatory activity; hence it appeared that EOs could also have anticancer effects as there is a relationship between the production of reactive oxygen species to the origin of oxidation and inflammation that can lead to cancer. More than 100 EOs from more than 20 families of plants have been tested on more than 20 different types of cancers in the past 10 years [94]. Bourgou and collaborators showed that the EO from seeds of black cumin (*Nigella sativa* L.) significantly inhibits the growth of A-549 and DLD-1 cancer cell lines with IC50 values of 43.0 and 46.0 μg/mL, respectively [95]. In 2012, Wang and collaborators reported the toxicology potential of EO of *Rosmarinus officinalis* L. and its three main components (including *α*-pinene, *β*-pinene, and 1,8-ceneole) toward three human cancer cell lines: the EO showed a strong cytotoxicity toward the three cancer cells with IC50 values of 0.025, 0.076, and 0.13‰ (v/v) on SK-OV-3, HO-8910, and Bel-7402, respectively [96].
