Allelochemicals Biologica... - Name

THE ALLELOPATHIC POTENTIAL OF GINSENOSIDES 165
pathogens, are ascomycetes. The activity of ginsenosides against these pathogens, as
well as saprotrophic Trichoderma spp., was evaluated in vitro (Nicol et al., 2002;
unpublished data). The Trichoderma spp. are potential antagonists towards soilborne
pathogens, evident by the greater levels of Trichoderma spp. found in healthy ginseng
fields than in replanted ginseng fields with high disease incidence (Shin and Lee,
1986). In vitro anti-fungal bioassays were completed by adding ginsenosides to growth
media and comparing the relative growth to that of controls (i.e., with no ginsenoside
addition to the growth media). Under these conditions, the growth of six of the nine
tested organisms was inhibited. The highest growth inhibition was observed in the
saprotrophs T. harzianum and T. hamatum followed by the leaf pathogen A. panax
and T. viride (Table 1).
Table 1. Growth Response of Selected Fungal and Oomycotan Species to
Ginsenosides. The relative growth of the microorganisms was compared in vitro with
and without the addition of ginsenosides isolated from Panax quinquefolius roots.
Growth was standardized to that of controls (i.e., no ginsenosides added) to allow
comparisons across species, even though different assay conditions were used for
different organisms. Growth data is shown as a mean ± standard deviation. With the
exception of F. oxysporum, the growth of all organisms in the presence of ginsenosides
was significantly different from the mean growth of the respective controls (data not
shown). Data compiled from Nicol et al. 2002, 2003 and unpublished data.
Fungal Species % Growth relative to control
Trichoderma harzianum -26.4 ± 0.9
Trichoderma hamatum -22.2 ± 2.8
Trichoderma viride -9.4 ± 1.1
Alternaria panax -17.1 ± 3.8
Fusarium solani -3.3 ± 0.6
Fusarium oxysporum -3.0 ± 0.8
Cylindrocarpon destructans +7.6 ± 2.9
Phytophthora cactorum +324.9 ± 1.0
Pythium irregulare +392.8 ± 0.5
The growth of the two Fusarium species, F. oxysporum and F. solani, was consistently
found to be slightly lower, but not always significantly different from control
(Table 1). Conversely, the growth of the causal organisms of some of the most devastating
diseases in the North American ginseng industry (i.e., C. destructans, P.
cactorum and Py. irregulare) was significantly stimulated over that of control. When
analysed as a group, significantly different growth responses to the ginsenosides were
observed across the fungal and oomycotan species tested (Table 1). That is, the organisms
tested were generally inhibited (Trichoderma spp. and A. panax), unaffected
(Fusarium spp.) or stimulated (C. destructans, P. cactorum and Py. irregulare) by
ginseng saponins. By comparison, greater antifungal activity was found with aescin,
a mixture of saponins from the horse chestnut tree (Nicol et al. 2002) and consequently,
ginsenosides can only be considered to be mildly antifungal.