Luteolin (3,4,5,7-tetrahydroxyflavonoid) is a natural flavonoid, named after it was originally isolated from the luteolin Reseda odorata Linn. in the Oleaceae family. It can be seen from the structure that luteolin is a polyphenolic hydroxyl compound with poor lipophilicity. Due to the intermolecular force between the hydroxyl groups, the lattice energy is high, and its hydrophilicity is also poor. Due to its special structure, The low solubility in various solvents poses certain challenges for its preparation and application.
How to extract luteolin?
Extraction process
The extraction technology of luteolin can be divided into two categories, traditional extraction technology, and new extraction technology. The new technology can be divided into direct extraction and extraction after raw material pretreatment. The former includes an ultrasonic-assisted method, microwave-assisted method, and supercritical fluid method. The extraction method and ionic liquid synergistic extraction method; the latter has an enzyme-assisted method and steam explosion pretreatment method, in order to obtain luteolin in high yield and stable quality.
1 Solvent extraction method
The solvent extraction method is a more traditional extraction method, which is divided into immersion method, percolation method, water decoction method, reflux extraction method, and continuous extraction method. At present, the extraction method commonly used for luteolin is reflux extraction, and the solvent is mostly 60% to 80% methanol or ethanol.
In the related reports on solvent extraction, some scholars have extracted luteolin from medicinal plants such as Vitex Chinensis, blackberry, Du Honghua, Prunella vulgaris, and Duyiwei, and the extraction rate is 1% to 3%.
2 Ultrasound-assisted method
The ultrasonic-assisted method uses the high-speed, strong cavitation effect and stirring effect generated by the sound wave, thereby destroying the cellular structure of the raw material, accelerating the penetration of the solvent, shortening the extraction time, and improving the extraction rate. The advantages of this method are: (1) high extraction efficiency; (2) short extraction time; (3) low extraction temperature; (4) wide application; (5) fewer impurities in the extract, which is conducive to separation and purification; (6) extraction The process operation cost is low; (7) the operation is simple, and the equipment maintenance and maintenance are convenient
3 Microwave-assisted method
Microwave-assisted extraction is a new technology for material extraction using microwave energy. Environmental protection, wide application, and other characteristics. The main influencing factors of the process are the choice of solvent, liquid-solid ratio, microwave radiation time, microwave radiation power, degree of fragmentation, the influence of moisture or humidity in the material, and other factors that affect microwave extraction (strengthening).
4 Supercritical fluid extraction
Supercritical fluid extraction refers to the separation operation of extracting soluble components from solid or liquid using supercritical fluid as solvent. Supercritical fluid has a gas-like diffusion coefficient, liquid dissolving power, and surface tension of 0. It can quickly penetrate into solid substances and extract the essence of its components. It has the characteristics of high efficiency, non-oxidation, pure natural, and no chemical pollution.
5 Synergistic extraction of ionic liquids
Ionic liquids refer to salts that are liquid at or near room temperature and consist entirely of anions and cations, also known as low-temperature molten salts. In the current research, the cations are mainly imidazolium cations, and the anions are mainly halogen ions and other inorganic acid ions (such as tetrafluoroborate, etc.). It has excellent characteristics such as low saturated vapor pressure, wide liquid path, strong solubility, and can be designed and adjusted, and its recyclability is the key to becoming a green solvent, and it has broad application prospects.
6 Enzyme-assisted method
The principle of the enzyme-assisted extraction method is to use the high specificity of the enzyme reaction, select the corresponding enzyme, hydrolyze or degrade the components of the cell wall, destroy its structure, and make the encapsulated active ingredients suspend or dissolve in the solvent. , the enzyme is easily inactivated, and the reaction conditions must be mild. This method can significantly improve the extraction rate, and the influencing factors are generally the type of enzyme, enzymatic hydrolysis time, temperature, pH value, etc.
7 Steam explosion pretreatment method
Steam explosion pretreatment is an emerging physical pretreatment technology, which can reduce the degree of cellulose polymerization, partially degrade hemicellulose, soften lignin, and reduce the transverse bonding strength. The horizontal effect of simultaneously increasing its surface area and porosity results in an enhanced ability of enzymes to digest cellulose. Studies have shown that this technology can significantly improve the extraction rate of raw materials, and this technology has been widely used in oil, grain, and Chinese herbal medicine industries.
8 Collaborative extraction method
The synergistic extraction method refers to the use of two or more methods to synergistically extract raw materials to achieve complementary advantages of the methods in order to obtain the best extraction effect.
There are various combinations of methods in the synergistic extraction method. In the literature on the extraction of luteolin, some scholars use ultrasonic synergistic microwave extraction, ultrasonic synergistic enzymatic extraction, ionic liquid synergistic microwave-assisted extraction, and ionic liquid synergistic ultrasonic extraction. The raw materials used There are brocade lanterns, vines, peanut shells, corn silk, etc. Due to different materials, the extraction rate of luteolin is 0.1% to 0.3%. From the experimental results, the synergistic method has a greater improvement in the extraction rate than the traditional process. Compared with the new single method, the effect is different, and most of them are positive results. Although the operation of the synergistic extraction method is relatively complicated, the extraction efficiency is high and can complement each other's advantages. , with development and research prospects.
If you would like to know more about luteolin, please contact us directly via medical@ysgcn.com
