Study on biosynthesis of ginsenosides in the leaf of Panax ginseng by seasonal flux analysis

초록

Seasonal ginsenoside flux in the leaves of 5-year-old Panax ginseng was analyzed from the field-grown ginseng, for the first time, to study possible biosynthesis and translocation of ginsenosides. The concentrations of nine major ginsenosides, Rg1, Re, Rh1, Rg2, R-Rh1, Rb1, Rc, Rb2, and Rd, were determined by UHPLC during the growth in between April and November. It was confirmed total ginsenoside content in the dried ginseng leaves was much higher than the roots by several folds whereas the composition of ginsenosides was different from the roots. The ginsenoside flux was affected by ginseng growth. It quickly increased to 10.99±0.15 (dry wt%) in April and dropped to 6.41±0.14% in May. Then, it slowly increased to 9.71±0.14% in August and maintained until October. Ginsenoside Re was most abundant in the leaf of P. ginseng, followed by Rd and Rg1. Ginsenosides Rf and Ro were not detected from the leaf. When compared to the previously reported root data, ginsenosides in the leaf appeared to be translocated to the root, especially in the early vegetative stage even though the metabolite translocated cannot be specified. The flux of ginsenoside R-Rh1 was similar to the other (20S)-PPT ginsenosides. When the compositional changes of each ginsenoside in the leaf was analyzed, complementary relationship was observed from ginsenoside Rg1 and Re, as well as from ginsenoside Rd and Rb1+Rc. Accordingly, ginsenoside Re in the leaf was proposed to be synthesized from ginsenoside Rg1. Similarly, ginsenosides Rb1 and Rc were proposed to be synthesized from Rd.

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