Background: Rb1 is a ginsenoside steroid glycoside found exclusively in the plant
Panax ginseng. In an earlier report, we showed that Rb1 increased cell proliferation and reduced
VEGF (vascular endothelial growth factor) secretion by human retinal pigment epithelial
Objective: In the present study, we hypothesized that chemical modification of Rb1 changes the
level of VEGF secretion by ARPE19 cells.
Method:Three derivatives of Rb1 were chemically synthesized by hydrogenation (Rb1-H2
(Rb1-Acyl), and epoxidation (Rb1-Epoxy). Structural modifications were confirmed by 1
Nuclear Magnetic Resonance (NMR) spectra and Mass Spectrometry (MS). To test the biological
activity, chemically modified compounds were added to cell culture media and incubated for 72
hours at a concentration of 250 nM at 37°C. Conditioned media were collected and cells were harvested/
counted after treatment. Viable cell numbers were determined by the trypan blue dye exclusion
method and VEGF levels by Enzyme-Linked Immunosorbent Assays (ELISA).
Results: Consistent with the prior report, results of the present study show Rb1 increased cell proliferation
and decreased VEGF secretion. Similar to Rb1’s effect on cell proliferation, treatment
, Rb1-Acyl and Rb1-Epoxy resulted in an increase in cell numbers. In contrast to Rb1-
induced decrease in VEGF secretion, treatment with Rb1-H2
, Rb-Acyl and Rb1-Epoxy resulted in
increased VEGF levels.
Conclusion: Chemical modifications of the ginsenoside Rb1 significantly affect the biological activity
of VEGF secretion by ARPE19 cells. Additional SAR (Structure Activity Relationship) experiments
will be conducted to study the detailed mechanisms by which how specific modifications
of Rb1 functional groups alter biological activities.