How to extract total saponins from traditional Chinese medicine extracts
According to the nature and structure of saponins, solvent extraction can be used for their extraction. Saponins have strong hydrophilicity, and the extraction solvent can be water or ethanol or methanol with high polarity. The molecular structure of saponins may contain carboxyl groups, which are acidic and can react with bases to form salts and dissolve in water, so alkaline water can also be used as the extraction solvent. Different extraction solvents should be selected according to the nature of raw materials and the composition and structure of saponins. There are three kinds of extraction solvents commonly used in industrial production: water, dilute ethanol and ethanol.
(1) The water extraction method can be used to extract saponins with high polarity, soluble in water, and almost insoluble in ethanol. For starch content, containing lesssaponinThe raw material with less surface tension is better to use water or alkaline aqueous solution as the extraction solvent. Neutral saponins use water as the extraction solvent, while acidic saponins are more suitable to use dilute alkaline water as the extraction solvent. For some acidic saponins that are difficult to dissolve in cold water but easy to dissolve in alkaline aqueous solution, alkaline aqueous solution can also be used for extraction. After extraction, acid and acidification can be added to the water extraction solution to precipitate the saponins and precipitate them out. This method is used for industrial extraction of glycyrrhizic acid. The saponins can be extracted by this method with heat or cold. Special attention should be paid to controlling the liquid output coefficient when using water as the extraction solvent, because the volume of the extraction solution is too large, which will greatly increase the production cost and reduce the yield of the extracted product.
(2) Dilute ethanol extraction method, the concentration of dilute ethanol is generally controlled at 70%, which can be selected according to the nature of the raw material, the composition and structure of the saponin. Generally, 60% dilute ethanol is commonly used. This extraction solvent is more suitable for raw materials with high starch content, especially for the extraction of neutral saponins that are difficult to dissolve in water. Using dilute ethanol extraction scissors to prevent saponin foaming, while also reducing the leaching of water-soluble impurities and fat-soluble impurities.
(3) In the ethanol extraction method, the saponins with small polarity, insoluble in water or difficult to extract with dilute ethanol can be extracted with ethanol as a solvent. When the saponins with large polarity are extracted with water or dilute ethanol and there are too many impurities, they can also be extracted with ethanol. The advantage of this method is that there are fewer water-soluble impurities in the extraction solution, and the disadvantage is that there are more fat-soluble impurities in the extraction solution, but these fat-soluble impurities can be heated to dissolve the saponins in water during the recovery of ethanol and then precipitated and removed.
For some plants with more fat-soluble impurities, the process of refining and separating total saponins is simplified. Light gasoline, benzene or chloroform can be used to extract fat-soluble impurities first, and then ethanol can be used to extract saponins, and the extract can be concentrated and recoveredEthanolAfter cooling, the total saponin precipitate can be precipitated. The advantages of this method are that the content of saponins in the extract is high, there are few impurities, and the refining is relatively simple.
