title: An optimized microwave-assisted extraction method for increasing yields of rare ginsenosides fromPanax quinquefoliusL.
abstract: BACKGROUND
  Rare ginsenosides inPanax quinquefoliusL. have strong bioactivities. The fact that it is hard to obtain large amounts of rare ginsenosides seriously restricts further research on these compounds. An easy, fast, and efficient method to obtain different kinds of rare ginsenosides simultaneously and to quantify each one precisely is urgently needed.
  
  
  METHODS
  Microwave-assisted extraction (MAE) was used to extract nine kinds of rare ginsenosides fromP. quinquefoliusL. In this article, rare ginsenosides [20(S)-Rh1, 20(R)-Rh1, Rg6, F4, Rk3, 20(S)-Rg3, 20(R)-Rg3, Rk1, and Rg5] were identified by high performance liquid chromatography (HPLC)-electrospray ionization-mass spectrometry. The quantity information of rare ginsenosides was analyzed by HPLC-UV at 203 nm.
  
  
  RESULTS
  The optimal conditions for MAE were using water as solvent with the material ratio of 1:40 (w/v) at a temperature of 145°C, and extracting for 15 min under microwave power of 1,600 W. Seven kinds of rare ginsenosides [20(S)-Rh1, 20(R)-Rh1, Rg6, F4, Rk3, Rk1, and Rg5] had high extraction yields, but those of 20(S)-Rg3 and 20(R)-Rg3 were lower. Compared with the conventional method, the extraction yields of the nine rare ginsenosides were significantly increased.
  
  
  CONCLUSIONS
  The results indicate that rare ginsenosides can be extracted effectively by MAE fromP. quinquefoliusL. in a short time. Microwave radiation plays an important role in MAE. The probable generation process of rare ginsenosides is also discussed in the article. It will be meaningful for further investigation or application of rare ginsenosides.
authors.affiliation: Scientific Research Center, China-Japan Union Hospital of Jilin University, Jilin, China.
authors.forename: Hua
authors.initials: H
authors.lastname: Yao
authors.affiliation: College of Chemistry, Jilin University, Jilin, China.
authors.forename: Xuwen
authors.initials: X
authors.lastname: Li
authors.affiliation: College of Chemistry, Jilin University, Jilin, China.
authors.forename: Ying
authors.initials: Y
authors.lastname: Liu
authors.affiliation: College of Chemistry, Jilin University, Jilin, China.
authors.forename: Qian
authors.initials: Q
authors.lastname: Wu
authors.affiliation: College of Chemistry, Jilin University, Jilin, China.
authors.forename: Yongri
authors.initials: Y
authors.lastname: Jin
keywords: Panax quinquefolius L.; high performance liquid chromatography/mass spectrometry; microwave-assisted extraction; rare ginsenosides