The process of extracting calendula flavonoids from calendula extract.

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1. Introduction

Calendula, a well - known plant, is rich in a variety of bioactive components, among which flavonoids are of particular interest. Flavonoids possess numerous biological activities such as antioxidant, anti - inflammatory, and antimicrobial properties. The extraction of calendula flavonoids from Calendula Extract is not only important for the study of these bioactive substances but also has potential applications in the fields of medicine, cosmetics, and food. However, this extraction process is complex and requires careful consideration of various factors.

2. Solvent Selection

The solubility characteristics of flavonoids play a crucial role in solvent selection for extraction. Different solvents have different affinities for flavonoids.

2.1. Ethanol

Ethanol is one of the most commonly used solvents. It has relatively good solubility for calendula flavonoids. Ethanol is also a relatively safe solvent, which is suitable for applications in the pharmaceutical and food industries. Moreover, it can dissolve other bioactive components in Calendula Extract to a certain extent, which may be beneficial for the comprehensive utilization of calendula.

2.2. Methanol

Methanol has a strong dissolving ability for flavonoids. However, it is toxic, which restricts its application in some fields, especially in food - related extraction. But in laboratory research, methanol can be used for efficient extraction when proper safety precautions are taken.

2.3. Water

Water is a green and environmentally friendly solvent. Although the solubility of flavonoids in pure water is relatively low, under certain conditions, such as the addition of surfactants or in combination with other solvents, water can also be used for the extraction of calendula flavonoids. Water - based extraction is more suitable for applications where environmental protection and safety are highly emphasized.

3. Extraction Methods

There are several extraction methods available for calendula flavonoids from Calendula Extract, each with its own efficiency, advantages, and limitations.

3.1. Solvent Extraction

1. Procedure: In solvent extraction, the calendula extract is mixed with the selected solvent (such as ethanol or methanol). The mixture is then stirred or shaken for a certain period of time to ensure sufficient contact between the solvent and the flavonoids in the extract. For example, a typical extraction may involve adding a certain amount of calendula extract to ethanol in a ratio of 1:5 (extract:solvent), and then stirring the mixture at room temperature for 2 - 3 hours.
2. Advantages: It is a relatively simple and traditional method. It does not require complex equipment, and it can be carried out in most laboratories. The extraction efficiency can be relatively high if the solvent and extraction conditions are properly selected.
3. Limitations: The extraction time is usually long. It may also require a large amount of solvent, which may increase the cost and environmental impact. Moreover, the selectivity of this method may not be very high, which may lead to the co - extraction of other unwanted components.

3.2. Ultrasonic - Assisted Extraction

1. Procedure: Ultrasonic - assisted extraction utilizes ultrasonic waves to enhance the extraction process. The calendula extract and the solvent are placed in an ultrasonic bath or ultrasonic probe system. The ultrasonic waves create cavitation bubbles in the solvent, which collapse and generate intense local pressure and temperature changes. These changes can break the cell walls of calendula more effectively, facilitating the release of flavonoids into the solvent. For instance, an extraction may be carried out by adding calendula extract to ethanol and then subjecting the mixture to ultrasonic treatment at a frequency of 20 - 50 kHz for 15 - 30 minutes.
2. Advantages: It significantly reduces the extraction time compared to traditional solvent extraction. The ultrasonic energy can enhance the mass transfer process, resulting in higher extraction efficiency. It also has relatively good selectivity, which can help to reduce the co - extraction of impurities.
3. Limitations: The equipment for ultrasonic - assisted extraction is more expensive than that for simple solvent extraction. In addition, improper control of ultrasonic parameters may cause degradation of flavonoids due to excessive energy input.

3.2. Supercritical Fluid Extraction

1. Procedure: Supercritical fluid extraction uses supercritical fluids, usually carbon dioxide (CO₂), as the extraction solvent. The CO₂ is brought to its supercritical state (above its critical temperature and pressure). The calendula extract is then contacted with the supercritical CO₂ in an extraction vessel. The flavonoids are selectively dissolved in the supercritical CO₂, and then the flavonoid - rich CO₂ is separated from the extraction system by reducing the pressure or changing the temperature, causing the flavonoids to be deposited. For example, in a typical supercritical fluid extraction process, the pressure may be set at 10 - 30 MPa and the temperature at 35 - 60 °C.
2. Advantages: It is a green extraction method as CO₂ is non - toxic, non - flammable, and environmentally friendly. It has high selectivity, which can precisely extract flavonoids while minimizing the extraction of other unwanted components. The extraction process is relatively fast, and the extracted flavonoids are of high purity.
3. Limitations: The equipment for supercritical fluid extraction is very expensive, which requires a high initial investment. The operation process is also more complex, requiring strict control of temperature, pressure, and other parameters.

4. Optimization of Extraction Factors

To obtain high - quality calendula flavonoids, several factors need to be optimized during the extraction process.

4.1. Extraction Time

• The extraction time has a significant impact on the yield of flavonoids. In solvent extraction, if the extraction time is too short, the flavonoids may not be fully dissolved and released from the calendula extract. For example, in ethanol extraction, if the extraction time is less than 1 hour, the yield of flavonoids may be relatively low.
• However, if the extraction time is too long, it may lead to the degradation of flavonoids or the extraction of other unwanted components. In ultrasonic - assisted extraction, for instance, if the ultrasonic treatment time exceeds 45 minutes, some flavonoids may start to degrade due to excessive ultrasonic energy.

4.2. Extraction Temperature

• Temperature affects the solubility of flavonoids in the solvent and the stability of flavonoids. In general, an appropriate increase in temperature can improve the solubility of flavonoids, thus increasing the extraction yield. For example, in solvent extraction with ethanol, when the temperature is increased from room temperature (about 25 °C) to 40 - 50 °C, the extraction yield of flavonoids may increase.
• However, high temperatures can also cause the degradation of flavonoids. In supercritical fluid extraction, if the temperature exceeds the optimal range (e.g., above 60 °C when using supercritical CO₂), the stability of flavonoids may be affected, and the quality of the extracted products may decline.

4.3. Solvent - to - Material Ratio

• The solvent - to - material ratio determines the concentration gradient between the solvent and the flavonoids in the calendula extract, which affects the mass transfer process. A higher solvent - to - material ratio generally means a larger amount of solvent relative to the calendula extract. This can increase the extraction efficiency to a certain extent. For example, in solvent extraction, when the solvent - to - material ratio is increased from 3:1 to 5:1 (solvent:extract), the extraction yield of flavonoids may increase.
• However, a too - high solvent - to - material ratio may not only increase the cost of the solvent but also may lead to the extraction of more unwanted components. In addition, in some extraction methods such as supercritical fluid extraction, an excessive amount of solvent may also cause problems in the separation process.

5. Conclusion

The extraction of calendula flavonoids from calendula extract is a complex process that requires careful consideration of solvent selection, extraction methods, and optimization of extraction factors. Each extraction method has its own advantages and limitations, and different solvents are suitable for different applications. By optimizing extraction time, temperature, and solvent - to - material ratio, high - quality calendula flavonoids can be obtained more effectively. Future research may focus on further improving the extraction efficiency, reducing costs, and exploring new applications of calendula flavonoids.

FAQ:

Question 1: What are the common solvents used for extracting calendula flavonoids?

Common solvents include ethanol, methanol, etc. These solvents are often selected based on the solubility characteristics of flavonoids. Ethanol, for example, is a relatively safe and effective solvent that can dissolve calendula flavonoids well.

Question 2: How does ultrasonic - assisted extraction work in calendula flavonoid extraction?

Ultrasonic - assisted extraction utilizes ultrasonic waves to create cavitation effects. These cavitation bubbles collapse near the plant material, which helps to break the cell walls of calendula more effectively. This, in turn, enhances the release of flavonoids into the solvent, increasing the extraction efficiency compared to traditional extraction methods.

Question 3: What are the advantages of supercritical fluid extraction for calendula flavonoids?

Supercritical fluid extraction has several advantages. It can operate at relatively low temperatures, which is beneficial for the extraction of heat - sensitive flavonoids. Also, the supercritical fluid has high diffusivity and low viscosity, allowing for better penetration into the calendula extract and more efficient extraction of flavonoids. Additionally, it often results in a purer extract with fewer impurities.

Question 4: How does the extraction time affect the extraction of calendula flavonoids?

Extraction time is an important factor. If the extraction time is too short, not all of the flavonoids may be fully extracted from the calendula extract. However, if the extraction time is too long, it may lead to the degradation of flavonoids or the extraction of unwanted substances. An optimal extraction time needs to be determined experimentally to achieve the highest yield and quality of calendula flavonoids.

Question 5: What is the role of the solvent - to - material ratio in calendula flavonoid extraction?

The solvent - to - material ratio affects the extraction efficiency. A higher solvent - to - material ratio may initially increase the extraction of flavonoids as there is more solvent available to dissolve the flavonoids. However, after a certain point, increasing the ratio may not significantly improve the extraction and may also lead to higher costs and more difficult downstream processing. The appropriate ratio needs to be determined based on the nature of the calendula extract and the extraction method used.

Related literature

• Optimization of Calendula Flavonoid Extraction: A Review"
• "Solvent Selection for Calendula Flavonoid Extraction: A Comparative Study"
• "The Efficiency of Ultrasonic - Assisted Extraction in Calendula Flavonoid Isolation"