Ginseng Research Today is a free monthly online journal that collates and summarizes the latest research about Ginseng, including details on american ginseng, panax, benefits, side effects.

In vitro metabolism of ginsenosides by the ginseng root pathogen Pythium irregulare.

Yousef LF, Bernards MA

Department of Biology, University of Western Ontario, London, ON, Canada N6A 5B7.

The role of ginseng saponins (ginsenosides) as modulators or inhibitors of disease is vague, but our earlier work supports the existence of an allelopathic relationship between ginsenosides and soilborne microbes. Interestingly, this allelopathy appears to significantly promote the growth of the important ginseng pathogen, Pythium irregulare while inhibiting that of an antagonistic non-pathogenic fungus, Trichoderma hamatum. Herein we report on the apparent selective metabolism of 20(S)-protopanaxadiol ginsenosides by an extracellular glycosidase from P. irregulare. Thus, when P. irregulare was cultured in the presence of a purified (>90%) ginsenoside mixture, nearly all of the 20(S)-protopanaxadiol ginsenosides (Rb(1), Rb(2), Rc, Rd, and to a limited extent G-XVII) were metabolized into the minor ginsenoside F(2), at least half of which appears to be internalized by the organism. No metabolism of the 20(S)-protopanaxatriol ginsenosides (Rg(1) and Re) was evident. By contrast, none of the ginsenosides added to the culture medium of the non-pathogenic fungus T. hamatum were metabolized. The metabolism of 20(S)-protopanaxadiol ginsenosides by P. irregulare appears to occur through the hydrolysis of terminal monosaccharide units from disaccharides present at C-3 and/or C-20 of ginsenosides Rb(1), Rc, Rb(2), Rd and G-XVII to yield one major product, ginsenoside F(2) and one minor product (possibly G-III). A similar transformation of ginsenosides was observed using a crude protein preparation isolated from the spent medium of P. irregulare cultures.

Published 25 August 2006 in Phytochemistry, 67(16): 1740-9.
Full-text of this article is available online (may require subscription).

© 2004-2008 Ginseng Research Today. All Rights Reserved.