Anthocyanins are flavonoids in phenolic compounds, a water-soluble pigment that is widely found in plant petals, fruit tissues and in the surface cells of the stems and leaves. Its color varies with the pH which gives the nature of many plants bright colors. In the natural state, anthocyanins in the plant often combines to a variety of monosaccharides to form glycosides, which is known as anthocyanin.
This post is used to introduce some methods to extract anthocyanins.
Solvent extraction method
Solvent extraction method is a conventional one for anthocyanins, and the solvents used are methanol, ethanol, acetone, water or a mixed solvent. In order to prevent the degradation of anthocyanin during the extraction process, a certain concentration of hydrochloric acid or formic acid will be added into the extraction solvent. But in the evaporation, these acids will cause hydrolysis to acylated anthocyanins partially or completely. In addition, for the sample which may contain a fat-soluble component in the extract, organic solvent such as n-hexane, petroleum ether, ether should be used to extract. The traditional solvent extraction method costs long extraction time and has low production efficiency. Additionally, the hot solvent is easy to cause anthocyanin degradation and the decrease of physiological activity.
Pressurized solvent extraction
Pressure solvent extraction, also known as pressurized liquid extraction, rapid solvent extraction, is to improve the boiling point of the solvent with the help of through the external pressure, thereby increase the solubility of the material in the solvent and extraction efficiency. However, the PSE is mainly applied in the extraction studies of flavonoids, phenolic compounds and other antioxidant active components.
Aqueous solution extraction method
Anthocyanins extracted by organic solvent contains more toxic substances and cause pollution to environment. Therefore, aqueous solution came into being. With this method, plant material will be immersed in hot water under normal pressure or high pressure. And then the extract will be absorbed by non-polar macroporous resin. Or it can be extracted by deoxidized hot water, followed by ultrafiltration or reverse osmosis, concentrated to obtain crude extract.
Microbial fermentation extraction
This method uses bio-fermentation technology for the extraction of anthocyanins which is the strong penetration and effective combination between biological science and chemical production. Microbial fermentation use microbial or enzyme to achieve the anthocyanin-containing cell wall degradation. So that the cell body anthocyanins will be fully dissolved into the extract, increasing the yield and rate of extraction.
Other extraction methods
Other extraction methods include high-voltage pulsed electric field assisted extraction. The first two can be applied to the extraction of protein, nucleic acid and polysaccharide. And ultra-high pressure assisted extraction has been successfully used in the extraction of anthocyanins in grapes, and the comparison found that high pressure assisted extraction of anthocyanins and other polyphenols can improve the efficiency of nearly 50%.
These are some methods about extraction of anthocyanins.
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