Extraction is the first step in the study of naturally occurring compounds biological activities from plants, play an important and decisive role in the results and ultimate success of the study.
The extraction process is carried out by different methods including:
Traditional methods: extraction by Soxhlet apparatus, exhaustive extraction and gradual infiltration.
Modern methods: Extraction assisted by:
Ultrasonication Assisted Extraction (UAE) Pulsed Electric Field (PEF)
Enzyme-assisted Extraction (EAE) Microwave-assisted Extraction (MAE) Pressurized Liquid Extraction (PLE) Supercritical Fluid Extraction (SFE) 2.3.1. Traditional methods
2.3.1.1. Soxhlet extraction
It is a continuous high-temperature extraction process. For Soxhlet extraction, the solid sample is placed in a porous "measuring tube" housed in a chamber. The extraction solvent is heated in the bottom flask, vaporized into the sample tube, condensed in the condenser, and dripped back.
15 This method uses less solvent and takes less time to complete. The following are the general disadvantages of Soxhlet extract: Toxic and flammable liquid organic solvents must be used, and the extracted flavonoids must be heat stable. Several factors must be considered (temperature, solvent-to-sample ratio, and stirring speed).
2.3.1.2. Exhausted percolation
After preparing the medicinal herbs, soak the herbs remedies in the solvent in the drained water jar. After a definite period of time (based on the type of herbs remedies), drop the extract at the bottom, and at the same time additional is added solvent at the top by allowing the solvent to flow very slowly and continuously through the layer of herbs remedies lying on the bed. rest (do not stir). The solvent layer in the extraction jar is usually submerged about 3-4 cm beyond the surface of the medicinal subtance.
Simple percolation: It is a method of exhaustion that always uses a new solvent to extract the active ingredients in medicinal herbs until they are exhausted.
Fractional percolation : is a technique of depletion that employs dilute extracts to extract new batches (new herbs remedies) or to extract batches with different degrees of extraction.
Advantages:
- Extracted medicinal herbs.
- Save solvents (re-percolated).
Disadvantages:
- There are common disadvantages of the fractional extraction method: low productivity, manual labor.
- The procedure is more complicated than the immersion method.
- Consuming solvents (easy percolation).
16 2.3.1.3. Gradual extraction
During the procedure, the ground plant material is submerged in a sealed container containing a appropriate solvent. The samples were maintained at room temperature for a minium of three days and were constantly shook. Solvents soften and break down the plant's cell walls during this procedure, revealing soluble phytochemicals. After that, the mixture should be filtered as follows:
Advantages:
- The uncomplicated method, no special requirement for the laboratory equipment.
Disadvantages:
- Large solvent volume, lengthy processing duration, and the need for further purification. When it comes to pureness, advanced extraction technology should be considered.
2.3.2. Modern methods
2.3.2.1. Ultrasonication Assisted Extraction (UAE)
Ultrasonication assisted extraction are waves with frequencies from 20 kHz to 10 MHz, which can travel through solids, liquids and gases and cannot be felt by humans. In this extraction method, high-energy gas bubbles are generated that disrupt the cell wall structure of the material, thereby facilitating better release of the intracellular matter.
These waves are applied and used in two types of devices, which are transducers and ultrasonic baths to extract phenolic compounds from plants.
Besides the inherent parameters of ultrasonic devices (such as amplitude, frequency and wavelength), their power and intensity also have a lot of influence on the extraction process and these parameters need to be optimized. . The design and shape of the ultrasonic bath as well as the shape of the transducer can affect the extraction process.
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Advantages:
- Easy to use, low cost, high efficiency, low organic solvent consumption and reduced extraction time.
- It can be used as a simple and reliable process in a wide range of organic solvents for various phenolic compounds at large scale and industrial level.
Disadvantages: Must be applied on a large scale.
2.3.2.2. Pulsed Electric Microwave-assisted (PEF)
The Pulsed Electric Field (PEF) is a popular and expanding application of High Voltage Engineering. The pulsed electric field creates transmembrane potential in the cell membrane, increasing its conductivity and permeability. This rise in permeability results in reversible or permanent disintegration of the cell membrane. Both breakdowns are applied in biomedicine, the environment application, and food industry.
Advantage:
- Does not involve dewatering or drying process and no addition of chemicals, thus reduce the operational price
- No heating (non-thermal equipment) hence, use less energy - Less time
- Highly scalability
Disadvantage:
- The presence of air bubbles in the treatment chamber can impact dielectric breakdown, leading the PEF treatment to become less uniform.
- Depending on the intensity of the applied electric field, cell membranes might be reversible or irreversible during the electroporation mechanism.
- The PEF's efficiency is strongly dependent on the quantity of electric field intensity and electrode gap.
2.3.2.3. Enzyme-assisted Extraction (EAE)
The enzyme-assisted extraction approach breaks the cell wall of the source material to enhance extraction yield. This approach can be used with other
18 procedures to improve total bioactive recovery from source materials.
The EAE is based on the following factors: the type, dosage, and required condition of the enzymes; the process's time-temperature combination; plant material qualities such as particle size, water content, and chemical composition;
and the solvent-to-solid ratio (Azmir et al., 2013).
Enzymes have been utilized to improve flavonoid release from plant material while using as few solvents and heat as possible.
2.3.2.4. Microwave-assisted Extraction (MAE)
Microwaves are electromagnetic waves that range in frequency from 30 to 300 MHz. The thermal effect is caused by the continuous movement of polar molecules in matter under the influence of electromagnetic induction.
Advantages:
- Time and cost savings, high efficiency, and low organic solvent consumption.
- Extract multiple substances at the same time in a short period of time.
Disadvantages:
- Microwave energy-absorbing solvents are potentially explosive and difficult to apply on a large scale.