THE ALLELOPATHIC POTENTIAL OF GINSENOSIDES

Abstract

Abstract American ginseng (Panax quinquefolius L.) is a perennial herb valued for the medicinal properties of its large, fleshy tap root. These medicinal properties are purported to be due to the triterpenoid saponins, or ginsenosides, that accumulate to 3–6% of the root dry weight. We asked the question: what is the ecological role of ginsenosides in Panax species? In addressing this question, we have determined that ginsenosides, like other saponins, possess fungitoxic properties, although different fungi and oomycotan organisms appear to be differentially affected by them in vitro. In order to play an allelopathic role, however, ginsenosides must be present in the soil at biologically active (i.e., ecologically relevant) concentrations. Results to date support the hypothesis that ginsenosides are phytoanticipins and serve as host resistance factors. The success of certain pathogens (e.g., Pythium cactorum, Pythium irregulare, Cylindrocarpon destructans) on ginseng may arise from their ability to detoxify or otherwise utilize ginsenosides as a nutritive source or growth stimulating factor, while other soil borne organisms appear susceptible to their fungitoxic properties. Ginsenosides have been isolated from rhizosphere soil and root exudates suggesting that these compounds are involved in allelopathic interactions between the host plant and soil fungi. Ultimately this allelopathic interaction may influence the fungal diseases of ginseng.