Steroidal saponin

Oligosaccharides derived from spirostanes

Steroid saponins are a kind of Spirostane Oligomers derived from analogues Glycan 。 It is an important class of plants biological activity The study of steroidal saponins has always played an important role in the chemistry of natural products.

Chinese name: Steroidal saponin
Foreign name: Steroidal saponins

Definition: Oligosaccharides derived from a class of spirostanes
Type: Oligosaccharide

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brief introduction

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There have been many reports on the separation, identification and structure determination of steroidal saponins. According to incomplete statistics, about 200 kinds of natural steroidal saponins in nearly 150 plants have been studied. The aglycones of steroidal saponins contain 27 carbon atom Spirosterol or furostanol, mostly found in Monocotyledon Liliaceae, Lycoriaceae and Dioscoreaceae And other plants. Common Chinese medicine Anemarrhena asphodeloides 、 Asparagus 、 Ophiopogon japonicus 、 Paris polyphylla They all contain a lot of steroidal saponins. Since steroidal saponins are synthetic steroids acyeterion and Hormone drugs In the 1950s and 1960s, scholars at home and abroad have done a lot of work in searching for resources and improving technology. Up to now, China has been in mass production Dioscin Important countries of diosgenin, tigogenin and hecogenin. In the 1970s, with Separation technology With the rapid development of structural research means, people pay more and more attention to the chemical research of saponins, especially the research of saponins with large polarity, long sugar chain and complex structure. Soviet Union Vollerner et al. [1, 2] Liliaceae Allium Agave Steroidal saponins of plants have been studied and nearly 30 new structures have been found.

Extraction and separation

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Saponins are a kind of highly polar Macromolecular compound , difficult to crystallize, soluble in water and alcohol, Insoluble to Organic solvent In addition, many saponins with similar structure often coexist in the same plant, which increases the difficulty of separation and purification. Generally, use first methanol Or water content ethanol Extract, and then transfer alcohol extract Suspended in water, water saturated N-butanol Extract to obtain total saponins. Conventional normal silica gel is used for the separation of crude saponins column chromatography In addition, optional Inverted silica gel 、 Macroporous adsorption resin and Dextran gel Column chromatography can significantly improve the separation effect. Reverse phase column chromatography is often used in the separation and purification of saponins, the most commonly used is ODS (C18 reversed phase filler), this method mainly uses water and alcohol to elute in different proportions, which has good separation effect for compounds with high polarity, and has less adsorption on samples, which can reduce sample loss. Gel column chromatography is a separation developed in the 1960s Water solubility Common methods of compounds are mainly based on Molecular size Perform separation. When plant extracts It also contains saponins flavone , fenugreek essence and lactone When the composition is equal, it can be used Sephadex LH-20 Perform component separation. Macroporous adsorption resin is a porous polymer. Diaion HP-20, D-101 and RA resins are commonly used for crude separation of saponins. Suspend the ethanol extract in water, directly pass through the macroporous adsorption resin column, the saponins are adsorbed, and then elute with different concentrations of alcohol, the total saponins can be divided into several parts, and can be effectively removed chlorophyll 。 Sometimes it is difficult to solve all the separation problems by only one column chromatography method, so it often requires several methods to be used together to obtain a pure saponin to achieve satisfactory separation effect. With the emergence of various new fillers, the extraction, separation and purification of saponins have reached high efficiency and speed, and a series of structures and chemical property Very similar saponins. Liu Chenglai Four steroidal saponins of about yamogen were isolated from the rhizome of Dioscorea nipponica Dioscorea zingiberensis Five steroidal saponins were obtained from the rhizome of Diosgenin. Besides, we started from East One sisal Five glycosides of Tigogenin were isolated from the fermentation product of leaf juice [6, 7].

Structural research

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The structure research of steroidal saponins mainly includes two parts: sugar and aglycone. Early research on steroidal saponins mainly focused on aglycones, and now the structure of aglycones has been basically clear. Steroidal sapogenin is usually snail sterol The monohydroxy substitution is mostly at position 3, and when the F ring cracks, furostanol is formed. Conduct saponin acid hydrolysis , separating aglycones, and determining the type of aglycones through spectral determination. Known aglycones can pass Thin layer chromatography , mixing melting point and infrared spectrum By comparison.

There are many kinds of sugars in steroidal saponins, which are significantly different from triterpene saponins. More than 10 species have been found so far, including Hexose 、 Pentose , Deoxysugar Ketose 、 Uronic acid Etc. Among them D-glucose 、 D-galactose 、 D-xylose 、 L- Rhamnose and L-arabinose Most common. sugar chain Glycosides are mostly 3-hydroxy glycosides of aglycones. The original saponin is connected to a glucose 。 In the connection mode of sugar, when there are more than three sugar units, the sugar chains are mostly branched. Research on sugar structure is often used Spectral analysis （UV, IR , MS , ? JH1，D，Z?- NMR , ? JC13, D, Z? - NMR) and some chemical modification Reaction (acid hydrolysis Alkali hydrolysis 、 Enzymatic hydrolysis , methylation Acetylation , restore, etc.). In the past, the structural study of steroidal saponins mainly relied on the classical chemical reaction 。 For example, we usually use Enzymolysis To study furostanol saponins with F ring cracking, furostanol saponins and β - glucosidase are kept at 37 ° for 2h, and the glycoside bond at position 26 can be hydrolyzed, so that furostanol saponins can be converted into corresponding spirostanol saponins, and the glycoside bonds at other positions are mostly unchanged. In addition, the selection of specific enzymes for enzymatic hydrolysis can also determine the type of terminal sugar. Acid hydrolysis includes complete hydrolysis and partial hydrolysis. The saponin is hydrolyzed with 2N or 4N mineral acid, and the hydrolysate is subjected to thin layer chromatography or prepared into derivatives Gas chromatography The type of sugar can be determined by comparing with the standard monosaccharide. If carried out Thin layer scanning The proportion of various sugars can also be obtained by quantitative analysis with gas chromatography. For saponins with more sugar, dilute acid is used for partial acid hydrolysis, and a series of secondary glycosides with different sugars removed after hydrolysis can be separated and identified to determine the sugar connection order. Total methylation is used to determine the connection position between sugar and sugar, the configuration of glycoside bond and the conformation 。 Acetylation is widely used in the structural study of saponins, usually using Acetic anhydride - pyridine Carry out total acetylation, and measure the? According to JH1, D, Z? - NMR and H-HCOSY spectra, the hydrogen on the carbon connected with glycosidic hydroxyl group is located in the high field, while the hydrogen on other carbon connected with acetylated hydroxyl group is significantly shifted to the low field, which can be used to judge the connection position of sugar. With the continuous improvement and development of structure measurement technology, spectrum Our method shows its superiority day by day. Especially in the past 10 years nuclear magnetic resonance And mass spectrometry. Fast atom bombardment mass spectrometry (FAB-MS) can be used to obtain Molecular ion peak And a series of Molecular ion Sugarless Debris peak From which the order of connection between sugars can be determined. 2d nmr It provides a simple and rapid method to solve a series of structural problems in the study of glycoside bond configuration, connection order and connection position between sugar and sugar in steroidal saponins with more sugar. At present, we identify a saponin without hydrolysis and derivatization, as long as we determine the content of? JC13, G, Z? - NMR spectrum, C-H correlation spectrum and HMBC spectrum can get all the structural information of the sugar part. Therefore, it can save samples and time, and speed up the identification of compounds.

pharmacological activity

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natural Steroid saponin Of biological activity Research and clinical application, first patented by France, reported Dioscin Diosgenin and its glycosides have anti arthritis effect. front Soviet Union Of Scientific researchers Discover the Caucasus Dioscorea zingiberensis The saponin extract in has a cholesterol lowering effect, which has also been proved by clinical experiments. Ravikumer et al. [8] discovered in the 1980s Yunnan Baiyao The diosgenin in has anticancer activity. from Agave The new steroidal saponin (afromontoside) isolated from Dracaena afromontan has the activity of inhibiting KB cells [9]. In addition, the fibrin disaccharide synthesized by Pfizer Pharmaceutical Company of the United States for the steroid mother nucleus with tigogenin and Hecogenin has a strong lipid-lowering effect [10]. There are also many reports on the biological activity of steroidal saponins in China. For example, steroidal saponins isolated from Paris have the functions of hemostasis Immunomodulation , anti tumour And pair cardiovascular system The role of [11]. from Dioscorea collettii (Dioscorea collettii) Cholesterol lowering activity 。 from Dioscorea nipponica Dioscin from D. nipponica has obvious antitussive, expectorant and antiasthmatic activities. At present, different kinds of Dioscorea Plant is used as raw material to extract its total steroidal saponins as clinical Lipid-lowering drugs It has been produced by several factories, among which Dioscorea zingiberensis (D. zingibernesis) as raw material“ Peltate leaf Guanxinning ”, clinical treatment coronary heart disease 、 angina pectoris It has certain curative effect. Listed“ Di'ao Xinxuekang ”It is also a drug to reduce blood fat Huangshan herb (D. panthaica) rhizome A mixture of diosgenin extracted from raw materials, including monosaccharide Glycosides, disaccharides, etc., but the author has not yet proved that Active ingredient Report of.

Systematically study the chemical and biological activities of steroidal saponins, and search for active Lead compound To further develop into new drugs has always been our goal. But by Separation and purification In the work of steroidal saponins, we found that it is a time-consuming, laborious and uneconomical method to separate and purify the low content mixed saponins from plants one by one to obtain pure products, and then screen their pharmacological activities. Because the content of saponins in plants is very low, and separation process It is complex and difficult to be used for industrial production. Compared with saponins, sapogenin is easy to be separated, and the separation and purification process is easy to be industrialized. Therefore, steroidal sapogenin can be used as the parent nucleus, referring to the known connection mode of sugar in natural steroidal saponins, directional semi synthetic steroidal saponins can be used to screen pharmacological activities, and then the relationship between structure and activity can be studied to develop new drugs with good efficacy and little side effects. By carrying out Glycosylation To synthesize a large number of various saponins with pharmacological activity is not only conducive to the development of new drugs, but also can promote the further research of steroidal saponins. So the natural and semi synthetic steroidal saponins are Drug innovation One area worth developing.

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