Ginsenoside profiles and related gene expression during foliation in Panax ginseng Meyer

Abstract

Panax ginseng is one of the most important medicinal plants in Asia. Triterpene saponins, known as ginsenosides, are the major pharmacological compounds in P. ginseng. The present study was conducted to evaluate the changes in ginsenoside composition according to the foliation stage of P. ginseng cultured in a hydroponic system. Among the three tested growth stages (closed, intermediate, and opened), the highest amount of total ginsenoside in the main and fine roots was in the intermediate stage. In the leaves, the highest amount of total ginsenoside was in the opened stage. The total ginsenoside content of the ginseng leaf was markedly increased in the transition from the closed to intermediate stage, and increased more slowly from the intermediate to opened leaf stage, suggesting active biosynthesis of ginsenosides in the leaf. Conversely, the total ginsenoside content of the main and fine roots decreased from the intermediate to opened leaf stage. This suggests movement of ginsenosides during foliation from the root to the leaf, or vice versa. The difference in the composition of ginsenosides between the leaf and root in each stage of foliation suggests that the ginsenoside profile is affected by foliation stage, and this profile differs in each organ of the plant. These results suggest that protopanaxadiol- and protopanaxatriol (PPT)-type ginsenosides are produced according to growth stage to meet different needs in the growth and defense of ginseng. The higher content of PPT-type ginsenosides in leaves could be related to the positive correlation between light and PPT-type ginsenosides.

Keywords: HPLC; Panax ginseng; foliation stage; ginsenoside; hydroponics.

Fig. 1

Phenological growth stage of ginseng during foliation. Three-year-old ginseng plants hydroponically cultured in perlite and peat moss were sampled. For the ginsenoside analysis and RNA extraction, the leaf, main root, and fine root were sampled at different stages during foliation, including the (a) closed, (b) intermediate, and (c) opened leaf stages. (A) Closed-up leaf and inflorescence. (B) Whole plants during foliation stage.

Fig. 2

Ginsenoside contents of leaves from Panax ginseng during foliation. (A) Closed, intermediate, and opened leaf stages were considered in the ginsenoside analysis. Bar indicates 1 cm. (B) Total ginsenoside content in the leaves were analyzed. (C) The major individual ginsenosides in the leaves were analyzed. Vertical bars indicate the mean ± standard error from three independent experiments.

Fig. 3

Ginsenoside contents of roots from Panax ginseng during foliation. The total ginsenoside content in the (A) main root and (C) fine root was analyzed according to the closed, intermediate, and opened leaf stages in Fig. 1. The major individual ginsenosides in the (B) main root and (D) fine root were analyzed. Vertical bars indicate the mean ± standard error from three independent experiments.

Fig. 4

Expression of genes related to ginsenoside biosynthesis in leaves during foliation. The relative expression of (A) PgSS, (B) PgSE, and (C) PgDDS genes in closed, intermediate, and opened leaves was analyzed by real-time polymerase chain reaction. Vertical bars indicate the mean ± standard error from three independent experiments. (D) The ginsenoside biosynthetic pathway in ginseng. PPD, protopanaxadiol; PPT, protopanaxatriol.

Fig. 5

Summary of the changes in ginsenoside composition in the leaf (■), main root (●), and fine root (▴) during foliation as divided into the closed (A), intermediate (B), and opened (C) leaf stage. The black-boxed picture suggests the possibility for ginsenoside movement. PPD, protopanaxadiol; PPT, protopanaxatriol.