Resin adsorption technology in alkaloid trees
Alkaloids, also known as organic bases, are widely distributed in a variety of plant raw materials, and most of them have significant physiological activities. There are many types of alkaloids and their structures are very complex. There are estrophilic alkaloids and hydrophilic alkaloids, but their commonality is that they have certain alkalinity and can form salts with acids. Its alkalinity can be characterized by the value of pKa of its conjugated acid, and the value of pKa of alkaloids. The pKa value of alkaloids can change from < 0 to > 13, which shows that their alkalinity is very different. The molecular characteristics of alkaloids generally have a large hydrophobic part, which is adsorbed according to the hydrophobic mechanism. On the one hand, its amino groups have certain alkalinity, and on the other hand, there are unpaired electrons on the nitrogen atom, which can form hydrogen bonds with hydrogen on hydroxyl groups and can also complex with some metal ions. Therefore, it is conceivable that there can be a variety of separation methods for alkaloids, extraction, ion exchange or adsorption methods are all available methods, and there are a variety of resins to choose from in the adsorption method. In principle, the extraction process is more complicated, and the ion exchange method cannot be eluted with simple organic solvents. Adsorption method is a better method.
CamptothecinThe separation of camptothecin is a typical example. From the molecular structure, camptothecin belongs to a weak base, which has strong hydrophobicity under neutral and alkaline conditions. It is feasible to use a non-polar resin for adsorption. The extraction method is as follows: pulverize the camptotheca fruit, extract it with ethanol, filter it, recover the ethanol, and make the pH of the aqueous solution 8,: to reduce its water solubility. Then it is adsorbed with AB-8 resin, and the water solubility of the camptothecin is poor, so that the desorption effect with acetic acid-aqueous solution is extremely poor, while the desorption rate with 1:1 chloroform/ethanol solution is high, and the washing peak is very concentrated. When the pH of the desorption solution is adjusted to 3, the desorption rate can reach 96%. After the desorption solution is concentrated, dried, and recrystallized with chloroform/methanol (1:1), camptothecin with a purity of more than 90% can be obtained, and the product yield is about 3%.
Camptothecin can also be adsorbed with sulfonic acid cation exchange resins. Due to its strong adsorption force, it must be washed off with basic organic solvents. Weakly acidic carboxylic acid resins are adsorbed and eluted with ethanol like general adsorption resins. The advantage of using resistance ion exchange resins is to reduce the adsorption of hydrophobic impurities. However, impurities such as proteins and amino acids containing amino groups in the extract may be adsorbed. Considering the effect of practical application, no matter which resin is used, there must be a corresponding process to cooperate in order to give full play to its advantages and avoid its disadvantages.
The adsorption resin method can also be used for the separation of berberine.BerberineAlso known as berberine, is a quaternary amine base, with strong alkalinity, widely distributed in Coptis chinensis, three needles, yellow cypress and many other plants. Because of its strong alkalinity and high water solubility, it can be extracted with water, such as 10 grams of three needles coarse powder with 10% HzS04 infiltrated until a weak alkaloid reaction, collected about 160mL of exudate, neutralized with 10% NaOH to neutral, about 200mL after filtration, through a column containing 5g of non-polar adsorption resin, washed with water until the effluent was alkaloid reaction. Continue to wash out berberine with water until the effluent has no alkaloid reaction. Steam the eluent to a yellow powder o.59g. Then elute with methanol to obtain a brown gel o.33g. The content of berberine in the two products was 97% of the original drug.
Scopolamine is the main alkaloid in the roots and leaves of Belladonna belladonna. The aqueous solution of scopolamine was adjusted to pH > 6, the sediment was filtered off, adsorbed with XAD-4 resin, and then eluted with 60% -90% methanol aqueous solution or 50% -90% aqueous solution and then extracted with chloroform to obtain the pure product of scopolamine.
Caffeine is a central nervous system stimulant, and caffeine needs to be removed when tea polyphenols are made from tea leaves. Tea polyphenols contain --OH, while caffeine contains amino and carbonyl groups, so the adsorption resin containing --OH is used withcaffeineFor the characteristic of forming hydrogen bonds, polystyrene adsorption resins containing phenolic hydroxyl groups can be used to adsorb caffeine. Resins containing --S03 H can also form hydrogen bonds with caffeine for adsorption.
