Study On The Preparation Method Of Protopanaxatriol Type Minor Ginsenosides And Sapogenin

Ginsenosides, as the main functional components in the plants of panax, posess various pharmacological activities. Ginsenosides are triterpenoid saponins which consist two parts, i.e. the sapogenins and glycosyls, when they lost the glycosyls gradually by the degradation, they will be converted into a series of the minor ginsenosides and sapogenins. Recent studies have demonstrated that the minor ginsenosides and sapogenins, such as 20(R/S)-ginsenoside Rg2, 20(R/S)-ginsenoside Rh1, 20(R/S)-ginsenoside PPT, are more bioactive than ginsenoside Re and Rg1 that are not degraded. Therefore, their preparation, biological activity and application research have become a new research hotspot. But because of minor ginsenosides and sapogenins are rare in panax, we usually prepare them by degrading other ginsenosides in some ways. The methods of preparing 20(S)-ginsenoside Rg2,20(S)-ginsenoside Rh1 and 20(S)-PPT are well established, however, there’s no effective method to prepare 20(R)-ginsenoside Rg2, 20(R)-ginsenoside Rh1 and20(R)-PPT. Thus, in this paper, the methods of preparing this three ginsenosides have been studied deeply.In order to provide the standard samples for determining the contents in the following study of preparation methods, we firstly achieved two kinds of degration products from sodium hydroxide glycerol and acetic hydrolysate of the panaxatriol type saponins of leaves and stems of panax ginseng C.A.Mey. Then we isolated six compounds from the two degration products by silica gel and ODS colmn chromatography and preparative high performance liquid chromatography. The six compounds were identified as 20(S)-ginsenoside Rg2, 20(R)-ginsenoside Rg2,20(S)-ginsenoside Rh1, 20(R)-ginsenoside Rh1, 20(S)-PPT and 20(R)-PPT by NMR spectral analysis.On the basis of single-factor experiment, the orthogonal test was taken to studythe optimal conditions of preparing 20(R)-ginsenoside Rg2, 20(R)-ginsenoside Rh1,and 20(R)-PPT from panaxatriol type ginsenosides of leaves and stems of panax ginseng C.A.Mey. The study showed that, the optimal conditions to prepare20(R)-ginsenoside Rg2 are as follows: the ratio of sample to solvent was 1:20, the acetic acid concentration was 30%, hydrolyzed at 80℃ for 4 hours, the transformation rate from ginsenoside Re by this process was 24.29%. The optimal conditions to prepare 20(R)-ginsenoside Rh1 are as follows: the ratio of sample to solvent was 1:20,the acetic acid concentration was 50%, hydrolyzed at 110℃ for 2 hours, the transformation rate from ginsenoside Re and Rg1 by this process was 6.89%. The optimal conditions to prepare 20(R)-PPT are as follows: the ratio of sample to solvent was 1:20, the tartaric acid concentration was 0.15g/m L, hydrolyzed at 120℃ for 5hours, the transformation rate from ginsenoside Re and Rg1 by this process was12.04%. Under the three optimal conditions, the 20(R)-ginsenoside Rg2 are more than20(S)-ginsenosides, moreover, they have the advantages of simple, high yield, rapid speed and little pollution. So, it can give a valuable references for preparing20(R)-ginsenoside Rg2,20(R)-ginsenoside Rh1 and 20(R)-PPT.Previous studies reported the methods of preparing protopanaxatriol(PPT) are always to degrade the total ginsenosides, protopanaxatriol type ginsenosides or the monomeric compounds of them. In order to explore the possibility of produing sapogenin by degrading ginsenosides in the process of extracting ginsenosides, we try to prepare 20(S/R)-PPT from stems and leaves of panax ginseng C.A.Mey. directly,and investigate the concentrations of 20(S/R)-PPT production. On the basis of single-factor experiment, the orthogonal test was taken to study the optimal extraction techology of 20(S/R)-PPT from stems and leaves of panax ginseng C.A.Mey. by tartaric acid solution. The optimal extraction condition of 20(S/R)-PPT are as follows:the ratio of sample to solvent was 1:30, the tartaric acid concentration was 0.175g/m L,hydrolyzed at 120℃ for 2 hours, the transformation rate by this process was 2.62%.Although the conversion rate is low and requires further study aslo, the process could complete the extraction and degradation at the same time, and could offer a new research direction for preparing 20(S/R)-PPT.In addition, to ensure accuracy of theresults in the research, we establish a method for determining the contents of20(S)-PPT and 20(R)-PPT, the LODs were 0.41 and 0.38 μg.m L-1, the average recoveries were 87.95% and 89.08%(n=6), RSD were 3.26% and 2.92%, respectively.The resuls showed that the method has high sensitivity, good precision and accuracy.In conclusion, we deeply study the conditions to prepare 20(R)-protopanaxatriol type minor ginsenosides and sapogenin from panaxatriol type ginsenosides of leaves and stems of panax ginseng C.A.Mey. and from the leaves of panax ginseng C.A.Mey.for the first time, moreover we discussed the degradation mechanism. Our study could provide a new scientific basis for preparation and utilization of protopanaxatriol type minor ginsenosides.