**6.5 Microwave assisted extraction**

*Bioactive Compounds - Biosynthesis, Characterization and Applications*

*Comparing water distillation and microwave assisted water distillation of obtaining thyme essential oil.*

materials like oils which are insoluble in water and may decompose at their boiling point [30]. It consists of spraying with a certain amount of moisture on the plant material placed on the grid in a similar system to water distillation and allow steam transfer of the essential oils to occur [29]. The plant raw material is placed on a performed plate and the steam, generated by a separate boiler, volatilizes and carries essential oils as it passes through the plant material [29]. The vapors are then condensed in water cooling system only to be collected at the end of the cooler in a separate appropriate collector. Steam distillation is advantageous as it allows the vaporization of essential oils without reaching their boiling point [30]. Moreover, the boiler being kept in a separate chamber from the plant chamber keeps the ambient temperature at which the material to be

**46**

**Figure 14.**

**Figure 12.** *Steam distillation.*

**Figure 13.**

*Microwave assisted extraction.*

Microwave assisted extraction MAE is modern technique used in extraction. The first patent for MAE was in 1995for the extraction of a natural product using microwaves by Pare (**Figure 13**) [31].

The target for heating in dried plant material is the minute microscopic traces of moisture that occurs in plant cells. The heating up of this moisture inside the plant cell due to microwave effect, results in evaporation and generates tremendous pressure on the cell wall. The cell wall is pushed from inside due to the pressure and the cell wall ruptures. Thus, the exudation of active constituents from the ruptured cells occurs, hence increasing the yield of phytoconstituents [32]. MAE allows the boiling point to be reached earlier then supported water distillation as shown in **Figure 14**. It has also been determined that the amount and quality of essential oil obtained by microwave-assisted water distillation in 30 minutes is equivalent to the amount and quality of essential oil obtained in 4 hours and thirty minutes by water distillation [29]. Not only does MAE save time and energy, but it also is considered environment friendly as it uses very little or no solvents [31, 32].

## **7. Conclusion**

The rich composition of plants (EOs, primary and secondary metabolites) offers several advantages in the phytotherapy field, therefore the use for different therapeutic purposes.

The extraction method of bioactive molecules depends on several factors and also depends on the plant properties.

## **Acknowledgements**

Praise be to Allah, who guided us and helped us to complete this project, which would not have ended had it not been for God guidance.

We also address many thanks and appreciations to the professors Mr.Othmane Benkortbi, Mr.Mabrouk Hamadach, Mr.Yahia Belaissa, Mrs.Lefnaoui and Mrs. Yahoum for their tremendous generosity in sharing information, providing contacts and even some materials that we lacked. We are grateful!

We would like, as well, to thank Mr.Nesreddine Terkmane, a local herbs expert who helped, corrected and oriented us countless times.

Our acknowledgment is extended to the funding partners.

#### **Conflict of interest**

The authors declare no conflict of interest.

#### **Notes/thanks/other declarations**

We address the best most sincere thanks and appreciations to our families.

I, Achouak, am forever grateful for my parents Leila Gehlouz and Abderahmen, my lighted soul sister Melek and my two brothers Ismail and Abdeldjalil for their ever-lasting love and care, their unconditional support and their magical way of always turning hardships into something fun. Thank you!

I, Nassima, am pleased to extend sincere thanks and gratitude to my parents, a source of motivation and encouragement throughout my academic career, my sister and my twin soul Karima, who has always supported me, and my dear brothers Ahmed and Youcef.
