Investigation of the hydrolysis of ginsenosides by high performance liquid chromatography-electrospray ionization mass spectrometry.

The hydrolysis of ginsenoside standards and the crude extracts of ginseng has been investigated at different pH values (2.4-11.2) using high performance liquid chromatography-electrospray ionization mass spectrometry (HPLC-ESI-MS). The experimental results indicated that the pH value of aqueous solutions is an important factor in changing the composition of ginsenosides. For (20 S)-protopanaxadiol ginsenosides, ginsenosides with a large mass hydrolyzed to form hydrolysates (20 S)-Rg3 and (20 R)-Rg3 at pH 4.3. There were more hydrolyzed products observed at pH 3.3: (20 S)-F2, C-25,26 hydrated ginsenoside "C-Y1" and "C-Y2" (MW=802 Da) accompanied with (20 S)-Rg3, (20 R)-Rg3. At pH 2.4, only (20 R)-Rg3, (20 S)-F2, a small quantity of (20 S)-Rg3 and three C-25,26 hydrated ginsenosides were obtained. For (20 S)-protopanaxatriol Re, no hydrolysates were observed at pH 4.3; it was hydrolyzed at pH 3.3 to form hydrolysates (20 S)-Rg2, (20 R)-Rg2 and hydrated C-25,26 (MW=802 Da) and at pH 2.4 only C-25,26 hydrated ginsenosides "C-Y1" and "C-Y2" (MW=802 Da) were left in the solution. Similar hydrolysis reactions could be also observed for the crude extracts of ginseng. It showed that HPLC/ESI-MS is a fast and convenient method to study the hydrolysis of ginseng.