Ginsenosides and Biotic Stress Responses of Ginseng

Abstract

Ginsenosides are saponins that possess a sugar moiety attached to a hydrophobic aglycone triterpenoid. They have been widely studied for their various medicinal benefits, such as their neuroprotective and anti-cancer activities, but their role in the biology of ginseng plants has been much less widely documented. In the wild, ginsengs are slow-growing perennials with roots that can survive for approximately 30 years; thus, they need to defend themselves against many potential biotic stresses over many decades. Biotic stresses would be a major natural selection pressure and may at least partially explain why ginseng roots expend considerable resources in order to accumulate relatively large amounts of ginsenosides. Ginsenosides may provide ginseng with antimicrobial activity against pathogens, antifeedant activity against insects and other herbivores, and allelopathic activity against other plants. In addition, the interaction of ginseng with pathogenic and non-pathogenic microorganisms and their elicitors may trigger increases in different root ginsenosides and associated gene expression, although some pathogens may be able to suppress this behavior. While not covered in this review, ginsenosides also have roles in ginseng development and abiotic stress tolerance. This review shows that there is considerable evidence supporting ginsenosides as important elements of ginseng's defense against a variety of biotic stresses.

Keywords: Panax ginseng; Panax notoginseng; Panax quinquefolius; allelopathy; disease; ginsenosides; insects.

Figure 1

Effect of rusty root disease on specific ginsenosides. Percentage of ginsenoside by dry weight in the roots of 3- to 4-year-old P. quinquefolius roots collected from the field, with and without rusty root symptoms, based on the study by Rahman and Punja [47] (left), and percentage of ginsenoside by dry weight in the roots of 4-year-old P. quinquefolius roots collected from the field, with and without rusty root symptoms, based on the study by Campeau and Proctor [48] (right). Asterisks indicate significant differences.

Figure 2

Effect of Fusarium diseases on specific ginsenosides. Percentage of ginsenoside by dry weight in P. quinquefolius roots of unknown age, either non-inoculated (control) or inoculated with F. solani or F. oxysporum at 72, 96, and 120 h post-infection, based on the study by Jiao et al. [50] (left), and the percentage of ginsenoside by dry weight in the roots of 4-year-old P. quinquefolius vascular tissue inoculated with distilled water (control), F. solani, or F. oxysporum at 7 days post-infection, based on the study by Jiao et al. [51] (right). Asterisks indicate significant differences.

Figure 3

Effect of Glomus spp. on specific ginsenosides. Percentage of ginsenoside by dry weight in roots for the roots of 1-year-old P. quinquefolius roots that are non-inoculated (control) or inoculated with a mixture of spores of G. etuticatum and G. intraradices one year after inoculation, based on the study by Fournier et al. [60]. Asterisks indicate significant differences.

Figure 4

Effect of P. polymxa on specific ginsenosides. Percentage of ginsenoside by dry weight in the roots of 4-year-old P. ginseng roots inoculated with deionized water (control) or P. polymxa at 1 month post-inoculation, based on the study by Gao et al. [64]. Asterisks indicate significant differences.

Figure 5

Effect of B. altitudinis on specific ginsenosides. Percent ginsenoside by dry weight in roots of P. ginseng adventitious root cultures inoculated with deionized water (control) or B. altitudinis at 12 days post inoculation based on the study of Song et al. [65]. Asterisks indicate significant differences.

Figure 6

Effect of chitosan on specific ginsenosides. Percentage of ginsenoside by dry weight in the roots of 4-year-old hairy root lines of P. ginseng, with water (control) or chitosan treatment at 25 days post-treatment, based on the study by Palazon et al. [70]. Asterisks indicate significant differences.

Figure 7

Effect of A. panax or C. destructans extracts on specific ginsenosides. Percentage of ginsenoside by dry weight in the roots of tissue culture cells of P. quinquefolius with no treatment (control) or a crude mycelial extract of A. panax or C. destructans at 8 days post-treatment, based on the study by Yu et al. [71]. Asterisks indicate significant differences.

Figure 8

The effect of P. monteili, B. circulans, T. atrovirdae, or T. harzianum filtrates on specific ginsenosides. Percentage of ginsenoside by dry weight in the roots of root-forming callus of P. quinquefolius for nutrient broth (control-bacteria), potato dextrose broth (control-fungi), or 1.25 v/v% cell-free culture filtrates of the bacteria P. monteili and B. circulans, or fungi T. atrovirdae and T. harzianum at 15 days post-treatment, based on the study by Biswas et al. [74]. Asterisks indicate significant differences.

Figure 9

Summary of the genera of microbes or microbial products inducing significant increases in specific PPD and PPT ginsenosides. The specific ginsenoside is listed above each arrow and the genus of the microbe or microbial product is given adjacent to the arrow.