Preparation process of rutin.

1. Introduction

Rutin, also known as rutoside, is an important flavonoid glycoside. It has a wide range of applications in various fields such as pharmaceuticals, food additives, and cosmetics due to its antioxidant, anti - inflammatory, and capillary - strengthening properties. Therefore, the preparation of high - quality rutin is of great significance.

2. Selection of raw materials

2.1 Plant sources

• Buckwheat: Buckwheat is a widely cultivated crop. It contains a certain amount of rutin in its seeds, leaves, and stems. The rutin content in different parts of buckwheat may vary, but generally, it is a good source for rutin extraction.
• Sophora japonica: The flowers of sophora japonica are rich in rutin. In traditional Chinese medicine, sophora japonica has been used for a long time, and the extraction of rutin from its flowers has also attracted much attention.

2.2 Quality assessment of raw materials

• Rutin content: The higher the rutin content in the plant material, the more favorable it is for extraction. Therefore, accurate determination of the rutin content in different plant materials through methods such as high - performance liquid chromatography (HPLC) is necessary.
• Purity: The plant material should be as pure as possible, free from excessive impurities such as other flavonoids, phenolic acids, and contaminants. Impure raw materials may increase the difficulty of subsequent extraction and purification processes.
• Availability and cost: Consideration should also be given to the availability of plant materials on a large scale and their cost. For commercial production of rutin, plant materials that are easy to obtain and cost - effective are preferred.

3. Extraction methods

3.1 Solvent extraction

• Ethanol - water mixtures: Ethanol - water mixtures are frequently used solvents for rutin extraction. The ratio of ethanol to water can be adjusted according to the characteristics of the plant material and the solubility of rutin. For example, a mixture with a higher ethanol content may be more suitable for extracting rutin from plant materials with relatively low water solubility. The extraction process usually involves soaking the plant material in the ethanol - water mixture for a certain period, followed by filtration to obtain the extract containing rutin.
• Other solvents: In addition to ethanol - water mixtures, some other solvents such as methanol, acetone, and ethyl acetate have also been studied for rutin extraction. However, these solvents may have some limitations, such as toxicity (in the case of methanol) or relatively high cost (for ethyl acetate). Therefore, ethanol - water mixtures are still the most widely used solvents in practical applications.

3.2 Microwave - assisted extraction

• Principle: Microwave radiation can cause the polar molecules in the plant material and the solvent to rotate rapidly, generating heat. This heat can accelerate the dissolution of rutin from the plant material into the solvent, thereby shortening the extraction time. For example, in the extraction of rutin from sophora japonica flowers, microwave - assisted extraction can significantly reduce the extraction time compared to traditional solvent extraction methods.
• Advantages and disadvantages: The advantage of microwave - assisted extraction is its high efficiency, which can save time and energy. However, the equipment required for this method is relatively expensive, and the extraction process needs to be carefully controlled to avoid over - heating and degradation of rutin. In addition, the scale - up of microwave - assisted extraction for large - scale industrial production may also face some challenges.

3.3 Ultrasonic - assisted extraction

• Principle: Ultrasonic waves can cause cavitation in the solvent, which creates micro - bubbles. When these micro - bubbles collapse, they generate high - pressure and high - temperature regions locally, which can promote the release of rutin from the plant material. For example, in the extraction of rutin from buckwheat, ultrasonic - assisted extraction can improve the extraction efficiency.
• Advantages and disadvantages: The advantage of ultrasonic - assisted extraction is its simplicity and relatively low cost. It can be easily integrated into existing extraction processes. However, similar to microwave - assisted extraction, the extraction conditions need to be optimized to ensure the quality of rutin. Moreover, the ultrasonic power and extraction time need to be carefully controlled to avoid excessive extraction of impurities.

4. Purification methods

4.1 Crystallization

• Principle: After the extraction, the rutin - containing solution is concentrated to a certain extent. Then, by adjusting the temperature, pH value, and solvent composition, rutin can be made to crystallize out. For example, by slowly cooling the concentrated rutin solution, rutin crystals can gradually form. The purity of the rutin crystals obtained by crystallization can be relatively high, but it may still contain some minor impurities.
• Optimization of crystallization conditions: To obtain high - quality rutin crystals, the crystallization conditions need to be carefully optimized. This includes determining the appropriate concentration of the rutin solution before crystallization, the rate of cooling, and the type and amount of the seeding agent. For example, a too - fast cooling rate may lead to the formation of small and impure crystals, while a too - slow cooling rate may result in a long crystallization time.

4.2 Chromatography

• Types of chromatography: There are several types of chromatography that can be used for rutin purification, such as column chromatography, high - performance liquid chromatography (HPLC), and thin - layer chromatography (TLC).
  • Column chromatography: In column chromatography, a stationary phase (such as silica gel or an ion - exchange resin) is packed in a column, and the rutin - containing solution is passed through the column. Different components in the solution will have different affinities for the stationary phase and the mobile phase, and thus can be separated. Column chromatography can be used for large - scale purification of rutin, but it may require a relatively long time and a large amount of solvent.
  • HPLC: HPLC is a highly efficient and sensitive chromatography method. It can achieve high - resolution separation of rutin from other impurities. By using a suitable column and mobile phase, rutin can be purified to a very high level of purity. However, HPLC equipment is expensive, and the operation requires professional skills.
  • TLC: TLC is a simple and rapid chromatography method. It is mainly used for preliminary screening and qualitative analysis of rutin. By spotting the rutin - containing sample on a thin - layer plate and developing it with a suitable solvent system, different components can be separated and visualized. Although TLC cannot achieve large - scale purification like column chromatography and HPLC, it is very useful for quickly identifying rutin and evaluating the purity of the sample.
• Combination of chromatography methods: In some cases, a combination of different chromatography methods may be used to achieve better purification results. For example, column chromatography can be used first to remove most of the major impurities, and then HPLC can be used for further purification to obtain high - purity rutin.

5. Quality control of rutin

5.1 Purity determination

• HPLC analysis: HPLC is the most commonly used method for rutin purity determination. By comparing the peak area of rutin with that of other components in the chromatogram, the purity of rutin can be accurately calculated. The purity of rutin for pharmaceutical and food additive applications usually requires a high standard, generally above 95% or even higher.
• Other methods: In addition to HPLC, other methods such as UV - visible spectroscopy and mass spectrometry can also be used for purity determination. UV - visible spectroscopy can be used to measure the absorbance of rutin at a specific wavelength, and based on the Beer - Lambert law, an estimate of the rutin concentration and purity can be made. Mass spectrometry can provide more detailed information about the molecular weight and structure of rutin, which can also be used to assess its purity.

5.2 Identification of impurities

• Chromatographic methods: As mentioned above, chromatography methods such as HPLC and TLC can be used not only for rutin purification but also for impurity identification. By analyzing the chromatogram, the presence of other flavonoids, phenolic acids, and other possible impurities can be detected. The types and amounts of impurities need to be carefully monitored to ensure the quality of rutin.
• Spectroscopic methods: Spectroscopic methods such as infrared spectroscopy (IR) and nuclear magnetic resonance (NMR) spectroscopy can also be used for impurity identification. IR spectroscopy can provide information about the functional groups in rutin and possible impurities, while NMR spectroscopy can give more detailed information about the molecular structure and chemical environment of rutin and impurities.

6. Conclusion

The preparation of rutin involves a series of processes from raw material selection, extraction to purification. Each step is crucial for obtaining high - quality rutin. With the development of technology, more efficient and environmentally friendly extraction and purification methods are expected to be developed in the future, which will further promote the application of rutin in various fields.

FAQ:

Q1: What are the common plant sources for rutin extraction?

Common plant sources for rutin extraction include buckwheat and sophora japonica. These plants are rich in rutin and are often selected for the extraction process.

Q2: Why is solvent extraction used in the preparation of rutin?

Solvent extraction, such as using ethanol - water mixtures, is used because it can effectively dissolve rutin from plant materials. The solvents can penetrate the plant cells and separate rutin from other components in the plant, facilitating its extraction.

Q3: How does crystallization help in purifying rutin?

Crystallization is a purification technique that works based on the solubility properties of rutin. As the solution is cooled or concentrated, rutin forms crystals while impurities remain in the solution. The crystals can then be separated from the solution, resulting in a purer form of rutin.

Q4: What role does chromatography play in the purification of rutin?

Chromatography is used to separate rutin from other substances based on their different affinities for the stationary and mobile phases. It can effectively remove impurities and further purify rutin, ensuring high - purity rutin for various applications.

Q5: What are the applications of rutin in the pharmaceutical field?

Rutin has antioxidant, anti - inflammatory, and capillary - strengthening properties in the pharmaceutical field. It can be used in the treatment of conditions related to blood vessels, such as varicose veins, and may also have potential in other areas due to its biological activities.

Related literature

• The extraction and purification of rutin: A comprehensive review"
• "Optimization of rutin production from natural sources"
• "Rutin: Properties, extraction methods, and pharmaceutical applications"