Conversion of ginsenosides by Lactobacillus plantarum studied by liquid chromatography coupled to quadrupole trap mass spectrometry

- L. plantarum metabolizes ginsenosides by elimination of glucosyl residues.
- Glucosyl residues are eliminated by hydrolysis, or by elimination and dehydration.
- Glucosyl residues are selectively eliminated at the C-20 position.
- Conversion of ginsenoside Rb1 yields 20(S)-Rg3, 20(R)-Rg3, Rk1 and Rg5.
- L. plantarum preferentially catalyzes the simultaneous release of 2 glucosyl residues.

Ginsenosides are the active components responsible for the pharmacological properties of ginseng, a commonly used medicinal plant and food ingredient. This study aimed to determine the changes of ginsenosides during fermentation of ginseng extract or reference ginsenosides with Lactobacillus plantarum. Chemically acidified ginseng extracts served as controls. High performance liquid chromatography coupled with quadrupole-trap (Q-TRAP) mass spectrometry method was employed for analysis and quantification of ginsenosides, and for identification of metabolites. A total of 14 metabolites were identified; the quantification of metabolites was achieved by tandem mass spectrometry in MRM mode. Metabolism of L. plantarum removed glucosyl moieties from ginsenosides Rb1, Rd, and Re at the C-20 position to produce a racemic mixture of products. Remarkably, removal of glycosyl residues occurred not only by hydrolysis but also by dehydration to produce racemic mixtures of Δ20(21) or Δ20(22) products. Biotransformation occurred more rapidly with the di-substituted ginsenoside Rb1 when compared to the mono-substituted ginsenoside Rd. This study thus extends the knowledge of biotransformation of ginsenosides to produce bioactive derivatives.