**8.2 Innovative (non-conventional) techniques**

There is steady progress in the development of extraction technology in recent years. They are also known as advanced techniques with the most recently developed.

### *8.2.1 Microwave-assisted extraction (MAE)*

Microwaves are part of the electromagnetic spectrum of light with a range of 300 MHz to 300 GHz, and wavelengths of these waves range from 1 cm−1 to 1 m−1 [60]. These waves are made up of two perpendicular oscillating fields which are used as energy and information carriers.

*Extraction of Bioactive Compounds from Medicinal Plants and Herbs DOI: http://dx.doi.org/10.5772/intechopen.98602*

In this extraction process, the use of microwave energy results in faster heating. Due to the exposure of each molecule to the microwave field, its direct effects include, thermal gradients reduction, volume generation due to heat, equipment size reduction, because of the higher process rates, and thus increase in productivity, through better usage of the same equipment process volume [61]. MAE is a feasible green solvent extraction procedure as it uses water or alcohol at elevated temperature and controlled pressure conditions (**Figure 3**).

This procedure has demonstrated various benefits like ease to handle and understand steadiness. Many studies reported that MAE has higher yields and is significantly faster than conventional methods for extracting active substances from plant materials [48, 54, 62]. MAE can be presented as a potential alternative to the traditional soliliquid extraction techniques. A few of the potential advantages are as follow:

i. a lesser amount of solvent is required (few milliliters of solvent can be used);


MAE intensification needs special equipment to be functional, and electricity produces waves, leading to higher investments and higher operating costs than conventional methods [64]. Banar and collaborators extracted the bioactive compounds from *Urtica dioica* grown in Lebanon using conventional methods (maceration, reflux, Soxhlet, hydrodistillation, Ultrasound-Assisted Extraction (UAE) and

Microwave-Assisted Extraction (MAE)) with different solvents. Their results revealed that MAE was the most effective technique. The extraction time was reduced, the lesser solvent was used and the amount of extracted compounds was increased [65].
