Cyclic Nucleotide Phosphodiesterases as Possible Targets for Ginsenosides

Cyclic nucleotide phosphodiesterases (PDEs) represent the unique enzymatic system degrddinf cAMP and cGMP which play a major role in the regulation of cell physiology. To investigate a possible molecular mechanism of ginsenosides, their activities were evaluated on PDEs which are recently described is new therapeutic targets. PDEs are classified into 7 families according to their genes (PDEI to PDE7) and are differently distributed in tissues. The IC50 values of ginsenosides were determined on PDEI to PDE 5 chromatographically isolatetl from bovine aorta. The results show that total ginseng saponin extract preferentially inhibits PDE 1 and PDE4 at concentrations nearby 200 ug/ml. Protopanaxadiol (PPD) fraction acts preferentially on PDE4 with and IC50 value of 100 nlml and inhibits also PDEI and PDE5 at 14 to 2 fold higher concentrations, respectively. Protopanaxatriol (PPT) fraction preferentially inhibits PDE 1 with and IC50 value of 170 ug/ml. Compound Rgl, originated from PPT fraction, and RC3 (5) represent the most active compounds towards PDE 1 with IC50 values around 80 UM. However Rg3 (R), epimer of Rgl (5) has no effect on the various PDEs tested, excepted on PDE3 rich is sligthly sensitive Compound Rbl, originated from PPD, acts on both PDEI and PDE4. It if two fold less active than Rgl and Rg3 (5) on PDEI. Taken together, these results mainly suggest that PDEI and PDE4 inhibitions could be a molecular mechanism which would participate in ginsenoside mechanisms, especially the effect of PPD on blood vessel and on CNS.