Polyphenols are a class of polyhydroxy compounds widely found in plants, possessing various biological activities such as antioxidant, anti-inflammatory, and anticancer properties. Therefore, polyphenol extraction has received widespread attention. The following are some common polyphenol extraction methods:
Solvent Extraction
Solvent extraction is a commonly used method for extracting polyphenols, mainly including aqueous solvent extraction and organic solvent extraction. Aqueous solvent extraction is simple, low-cost, and yields high purity, but the extraction rate is low. Organic solvent extraction utilizes the differences in solubility of polyphenols in different solvents for reflux extraction. Commonly used solvents include methanol and ethanol. This method can improve the extraction rate and shorten the reaction time, but it has problems such as high cost, difficult recovery, and toxicity and flammability.
Microwave-Assisted Extraction
Microwave-assisted extraction technology uses microwave energy to improve the extraction rate. Microwave radiation causes polar substances within plant cells to absorb microwave energy, generating a large amount of heat. This rapidly raises the intracellular temperature, causing liquid water to vaporize and form tiny pores in the cell membrane and cell wall. This allows extracellular solvents to enter the cell, dissolve, and release intracellular substances. This method effectively improves yield, reduces reaction time, and decreases solvent usage. The equipment is also widely available, making it widely accepted.
Ultrasonic-Assisted Extraction
Ultrasonic-assisted extraction utilizes the strong vibrations, high acceleration, strong cavitation effect, and stirring action generated by ultrasound to accelerate the entry of active ingredients into the solvent, thereby increasing the extraction rate, shortening the extraction time, and avoiding the effects of high temperatures on the extracted components. This method is simple and quick to operate, with low extraction temperature, short time, and high extraction rate, and the extract structure is not easily damaged. However, the purity of the obtained product is not high.
Enzymatic Extraction
Enzymatic extraction technology utilizes the highly specific characteristics of enzyme reactions. Appropriate enzymes are selected to hydrolyze or degrade cell wall components such as cellulose, hemicellulose, and pectin, thereby disrupting the cell wall structure and allowing intracellular components to dissolve, suspend, or interdissolve in the solvent, achieving the extraction purpose. The biggest advantage of enzymatic extraction is its mild reaction conditions, resulting in products with high purity, stability, and activity, and no pollution. It also has advantages in shortening extraction time, reducing energy consumption, and lowering extraction costs.
Supercritical Fluid Extraction (SFE)
Supercritical fluid extraction is a green and efficient extraction technology that utilizes supercritical fluids, such as carbon dioxide, as the extractant. This method can be performed at near-room temperature, preserving the original structure and bioactivity of polyphenols, and offers advantages such as being pollution-free and energy-efficient. However, the high cost of SFE equipment and the stringent requirements for extraction conditions limit its widespread application.
Different polyphenol extraction methods exist. In practical applications, the appropriate extraction method must be selected based on factors such as the specific plant material, extraction target, and experimental conditions to improve the extraction efficiency and quality of polyphenols, laying the foundation for further research and application of polyphenols.
