Modification Of Oleanane-type Saponins And Their Structure-activity Relationship Against Magnaporthe Oryzae

Rice blast is a diseases on rice,it is caused by M.oryzae,Once the rice get the disease,It will decrease the rice yield,But the widely used chemical pesticides not only polluting the environment and it is easy to produce drug-resistant strains,and if the rice get the diseases again,it will make people harder to treatment.So it is significance to develop the enviornment friendly bio-pesticides.We found a saponin from Schima superba's leaf exhibit strong inhibit of M.oryzae in our previous studies.If we get the saponin just through the Schima superba's leaf,it take a high cost,so restricting the development of saponin.Therefore this study attemps to use the chemical modification way to achieve the diversification oleanane-type saponins and start the structure-activity relationship study.Acid hydrolysis of tea saponin,and then through the macroporous resin column purification twice,we obtain a single angeloyl oleanane theasapogenol?TS?;The fruit of Sapindus saponaria extraction by alcohol to obtain sapindus saponins,and then through After purification of the macroporous resin,acid hydrolysis was carried out to obtain the hederagenin.The purified sapogenin was eluted in a silica gel column to obtain a 5:1fraction saponins.In this paper,the first two substances were used as the start material.Five saponins were obtained and identified by ¹³C NMR and ¹H NMR.Of the chemical structure.5:1 fraction saponins were chemically modified with bromosil and7-bromo-1-heptene,respectively,and mixed saponins A and mixed saponins B were obtained respectively.The blast resistance activity of the two kinds of aglycones,5:1 fraction saponin,five saponins,mixed saponin A,mixed saponin B and some of the intermediate products were tested by mycelium growth rate method.The results showed that the chemical activity The antibacterial activity of the modified mixed saponin A was greatly enhanced,and the inhibition rate of rice blast was 52.83%in the concertration of 50 ppm.The results showed that the structure-activity relationship of rice blast resistance was as follows:?1?the most significant effect on the effect of saponin against M.oryzae is C3 chain glycosyl,which is almost decisive,in which the C3 chain is mainly reflected in the number and type of glycosyl groups;?2?the single glycose chain is better than double glycose chain,and if the glycose chain connetct the site of C3 will much better;?3?if some lipophilic group exist in E ring and C28 of Saponin,it is will enhance its resistance to M.oryzae activity,but the effect is less than the C3 position of the sugar;?4?C15 and C16 hydroxyl groups will also be beneficial to the agar resistance of M.oryzae.