Development Of Semisynthetic Soyasaponin Derivatives

Very recently, great interest in soyasaponins has been aroused because of its important biological activities. However, the natural structure of saponins may not stay in the best active state. To enlarge its application and deep research on relationship between structure and function, sugar chains of soyasaponins can be modified.In order to synthesis two kinds of derivatives with different degree on hydrophilic and hydrophobic, a method by modifying soyasaponin’s C-3-O glucose carboxyl acid group was ascertained.The paper mainly contains two parts. The objective of first part was combine soyasaponin Ab with ethylenediamine and L-proline by amide linkage, obtained derivatives in form of “Ab- ethylenediamine” and “Abethylenediamine-L-proline”. Preliminary judgment for the derivatives have been synthesized after validation molecular weight by mass spectrum. For derivatives dissolve in acidic water showing positive charged, proved with liquid chromatographic retention time, their degrees of hydrophilic were improved obviously.In the second part, the same as above, soyasaponin was also catalyzed by carbodiimide, linking with different functional group, derivatives in form of “Ab-dodecylamine, Ab-phenylethylamine and Ab-ethylenediaminePhenylpropionicacid” were obtained respectively. The synthesized derivatives of soyasaponin Ab with weak polarity and their structure were verified by IR,EMI/MS, and NMR.The catalytic method of synthesizing derivatives by carbodiimide was confirmed. Hydrophobic Dicyclohexylcarbodiimide(DCC) or hydrophilic N-(3-Dimethylaminopropyl)-N’-ethylcarbodiimide hydrochloride(EDC) was dissolved in pyridine or dimethylformamide(DMF), respectively. After the addition of N-hydroxysuccinimide(NHS) and soyasaponin Ab, various compounds containing functional group was added. Then the reactions were carried out with mixing at room temperature for 3 days. For hydrophilic derivative, detection and identification was done directly after reaction, while for hydrophobic derivatives, pure water was firstly added to terminate reaction. After 1 day, ethyl acetate was added to extract derivative, which was then tested and evaluated by HPLC.Structural modification for sugar chain of saponin can change the structural configuration and polarity. Derivatives can be used for further investigation about the relationship between immunostimulating adjuvant/haemolytic activities and molecular structure of soyasaponins. In addition, the achievement of saponin-functional group conjugates have also a certain reference value for derivatization of other saponins based on 3-O-glucoronic acid carboxylic group.