Common extraction methods for plant extracts

 

There are six common extraction methods for plant extracts: solvent extraction, ultrasonic extraction, microwave extraction, enzyme extraction, supercritical fluid extraction and microwave-assisted extraction.
Among them, supercritical fluid extraction and microwave-assisted extraction are widely used as new extraction technologies.
1. Solvent extraction method
Solvent extraction method is to use solvent to extract effective ingredients from solid raw materials. The solvent used must have the characteristics of being miscible with the extracted solute. After the plant material is crushed, it is placed in a suitable container and several times the amount of solvent is added. It can be extracted by immersion, percolation, decoction, reflux and continuous extraction.
In the extraction process of solvent extraction, the concentration of solvent, material-liquid ratio, extraction temperature and extraction time will directly affect the extraction rate of effective ingredients.
2. Ultrasonic extraction method
Ultrasonic extraction uses the strong vibration and cavitation effect generated by ultrasound to accelerate the release, diffusion and dissolution of substances in plant cells into the solvent, while keeping the structure and biological activity of the extracted substances unchanged. The principle of ultrasonic extraction is mainly a physical process, which is a newer extraction method that has gradually received attention in recent years. For most components, the ultrasonic extraction method can significantly shorten the extraction time compared with conventional solvent extraction, consume less solvent, and have a high leaching rate, so it has a higher extraction efficiency.
In the ultrasonic extraction process, the selection and concentration of the solvent, the material-liquid ratio, the extraction temperature, and the extraction time will directly affect the extraction rate.
3. Microwave extraction method
Microwave extraction method, also known as microwave extraction, is also called microwave assisted extraction (MAE). It refers to the technology and method of extracting various chemical components from plants, minerals, animal tissues, etc. in a microwave reactor using appropriate solvents. Microwave refers to electromagnetic waves with a frequency of 300MHz to 300GHz. It uses the electromagnetic field to effectively separate certain organic components in solid or semi-solid substances from the matrix and maintain the original compound state of the analyzed object.
4. Enzyme extraction method
Enzyme extraction method is a method that uses cellulase, pectinase, protease, etc. (mainly cellulase) to destroy the cell wall of the plant to promote the maximum dissolution and separation of the effective components of the plant. In the extraction process of enzyme extraction, the selection of enzymes, enzyme concentration, pH value, enzymolysis temperature, and enzymolysis time will affect the extraction rate of plant extracts.
5. Supercritical fluid extraction method
Supercritical fluid extraction (SFE) is a method of extracting certain effective components from solids or liquids and separating them using supercritical fluid as solvent.
Supercritical fluid (SF) refers to a gas (liquid) or gas (liquid) mixture whose density is close to that of liquid when the operating pressure and temperature are both higher than the critical point, and whose diffusion coefficient and viscosity are close to that of gas, and whose properties are between gas and liquid.
The characteristic of supercritical fluid extraction is to make full use of the characteristics of supercritical fluid that it has both gas and liquid properties. Near the critical point, the solubility of supercritical fluid for components changes continuously with the pressure and temperature of the system, so that the solubility of components and the selectivity of solvent can be easily adjusted. Supercritical fluid extraction has the following characteristics: no phase change process of materials, so energy saving is obvious, the process flow is simple, the extraction efficiency is high, there is no organic solvent residue, the product quality is good, and there is no environmental pollution.
6. Microwave-assisted extraction method
Microwave-assisted extraction technology (MAE) is a new technology that uses microwave energy to improve extraction efficiency. Microwave-assisted extraction is a method of selectively extracting target components from materials using the characteristics of microwave heating. By adjusting the parameters of microwaves, the target components can be effectively heated to facilitate the extraction and separation of the target components. The principle of microwave-assisted extraction of plants is that plant samples absorb a large amount of energy in the microwave field, while the surrounding solvent absorbs less, thereby generating thermal stress inside the cells. Plant cells rupture due to the internal thermal stress, so that the substances inside the cells are directly in contact with the relatively cold extraction solvent, thereby accelerating the transfer of target products from the inside of the cells to the extraction solvent, thereby strengthening the extraction process. The technical principle of microwave-assisted extraction is the same as soaking and filtration, but the speed of extracting plant extracts is much faster than traditional methods, which reduces the extraction time while avoiding the destruction and degradation of valuable plant extracts. At present, microwave-assisted extraction has become a powerful tool for extracting active ingredients from natural plants with its fast extraction speed and good extract quality, but microwave-assisted extraction is selective internal heating and requires the processed materials to have good water absorption. In other words, the position of the product to be separated is easy to absorb water, otherwise it is difficult for the cells to absorb enough microwaves to break themselves, and the product is difficult to release quickly. For liquid extraction systems, the solvent substance is required to be polar, and non-polar solvents are insensitive to the effects of microwaves.

 

The main methods for extracting salidroside are: water extraction, microwave-assisted extraction, ultrasonic extraction, and supercritical CO2 extraction combined with the above three methods.

Different extraction methods and effects of salidroside
1. The extraction rate of salidroside obtained by supercritical C02 extraction-water extraction is the highest. The water extraction method mainly investigates the effects of solid-liquid ratio, extraction time and extraction temperature on the extraction rate of salidroside.
For supercritical CO2 extraction-water extraction, the effects of extraction pressure, extraction temperature, extraction time and entrainer concentration of supercritical CO2 extraction on the extraction rate are mainly investigated. The optimal supercritical C02 extraction conditions are: extraction pressure 40 MPa, extraction temperature 55℃, entrainer 7 mL anhydrous ethanol, extraction time 5 h, and the extraction rate of salidroside reaches 99.6%.
2. Microwave-assisted extraction method mainly investigates the effects of solid-liquid ratio, immersion time, microwave power, microwave treatment time and magnetic stirring time on the extraction rate of salidroside.
3. The ultrasonic extraction method mainly investigated the effects of solid-liquid ratio, immersion time, ultrasonic power, ultrasonic time and ultrasonic temperature on the extraction rate.
4. The method of separating and purifying salidroside by macroporous adsorption resin was studied. By studying the physical properties of the resin and the adsorption and desorption capacity of salidroside, the highly polar DA-201 was selected to purify salidroside. Then the dosage of DA-201, the flow rate during adsorption, the concentration of the desorbent, the dosage of the desorbent and the optimal flow rate during desorption were determined. The results showed that the optimal process conditions were: the adsorbent dosage was 5 mg salidroside/g dry resin, the adsorption flow rate was 1 BV/h; the desorbent was selected as an ethanol solution with a mass fraction of 10%, the desorption flow rate was 2 BV/h., and the desorbent dosage was 16mL/g dry resin. Under the above process conditions, the purity of the obtained salidroside was 99%.

 

UV detection of shikonin and other plant extracts

[Product name]: Shikonin

[Specification]: 98%

[Other product names]: Shikonin, Shikonin, Shikonin

[Cas number]: 517-89-5

[Molecular formula]: C16H16O5

[Molecular weight]: 288.31

[Detection method]: UV

UV detection is one of the commonly used detection methods for shikonin and other plant extracts. UV is the abbreviation of the English name ultraviolet. UV detection is also called ultraviolet detection and ultraviolet spectrum detection. UV detection is mainly used for the determination of the composition of the complex and its stability constant, quantitative analysis, structural analysis, qualitative analysis, application scope definition Ultraviolet spectrum is a spectrum generated by certain valence electrons in the molecule absorbing electromagnetic waves of a certain wavelength, jumping from low energy level to high energy level. When the electrons in the molecule absorb energy, they will jump from the ground state to the excited state, and then release energy (radiate characteristic spectral lines) and return to the ground state; and the wavelength of the characteristic general line radiated in the ultraviolet region is called ultraviolet spectrum (UV). UV light comes from a mercury UV lamp, which is captured through a sapphire window and process flow. Except for specific UV wavelengths, a narrow band is blocked by a UV filter to block all transmitted light. This UV light can pass through the filter and the test detector to record only the specific UV wavelength. The UV light passes directly through a UV filter of the same specifications close to the lamp. The reference detector is placed behind the filter to test the current UV intensity. The reference detector signal is used to compensate for the fluctuations in the intensity of the UV resource caused by lamp aging, extreme temperature changes, etc. The photocurrent results given by the measurement and reference detectors will be amplified, modified, and processed by the transmitter. The transmitter provides calculated measurement results in real time and can send multiple output values ​​to the process control system. 1. Qualitative analysis In the qualitative analysis of organic compounds, UV-visible spectroscopy is suitable for the identification of unsaturated organic compounds, especially conjugated systems, to infer the skeleton structure of unknown substances. In addition, it can be combined with infrared spectroscopy, nuclear magnetic resonance spectroscopy and mass spectrometry for qualitative identification and structural analysis, so it is still a useful auxiliary method. Generally, there are two qualitative analysis methods: comparing the absorption spectrum curve and calculating the maximum absorption wavelength λmax by empirical rules, and then comparing it with the measured value. 2. Structural analysis Structural analysis can be used to determine the configuration and conformation of a compound. For example, distinguishing cis-trans isomers and tautomers. 3. Quantitative analysis The basis of UV-visible spectrophotometric quantitative analysis is the Lambert-Beer law, that is, the absorbance of the substance being measured at a certain wavelength is linearly related to its solubility. Therefore, by measuring the absorbance of the solution to incident light of a certain wavelength, the concentration and content of the substance in the solution can be calculated. Commonly used determination methods include: single-component quantitative method, multi-component quantitative method, dual-wavelength method, differential spectrophotometry and derivative spectroscopy.