Natural Products from Panax ginseng

Characterization of UDP-glycosyltransferase involved in biosynthesis of ginsenosides Rh1 and Rd and identification of critical conserved amino acid residues for its function.[Pubmed: 30095259]

Ginsenosides attract great attention for their bioactivities. However, their contents are low, and many UDP-glycosyltransferases (UGTs) that play crucial roles in the ginsenosides biosynthesis pathways have not been identified, which hinders the biosynthesis of ginsenosides. In this study, we reported one UDP-glycosyltransferase, UGTPg71A29 from Panax ginseng could glycosylate the C20-OH of Rh1, and transfer a glucose moiety to Rd, producing ginsenoside Rg1 and Rb1, respectively. Ectopic expression of UGTPg71A29 in Saccharomyces cerevisiae stably generated Rg1 and Rb1 under its corresponding substrate, respectively. Overexpression of UGTPg71A29 in transgenic cells of P. ginseng could significantly enhance the accumulation of Rg1 and Rb1 with their contents of 3.2-fold and 3.5-fold higher than those in control, respectively. Homology modeling, molecular dynamics and mutational analysis revealed the key catalytic site, Gln283, which provided insights into the catalytic mechanism of UGTPg71A29. These results not only provide an efficient enzymatic tool for the synthesis of glycosides but also help achieve large-scale industrial production of glycosides.

Identification of candidate UDP-glycosyltransferases involved in protopanaxadiol-type ginsenoside biosynthesis in Panax ginseng.[Pubmed: 30082711]

Ginsenosides are dammarane-type or triterpenoidal saponins that contribute to the various pharmacological activities of the medicinal herb Panax ginseng. The putative biosynthetic pathway for ginsenoside biosynthesis is known in P. ginseng, as are some of the transcripts and enzyme-encoding genes. However, few genes related to the UDP-glycosyltransferases (UGTs), enzymes that mediate glycosylation processes in final saponin biosynthesis, have been identified. Here, we generated three replicated Illumina RNA-Seq datasets from the adventitious roots of P. ginseng cultivar Cheongsun (CS) after 0, 12, 24, and 48 h of treatment with methyl jasmonate (MeJA). Using the same CS cultivar, metabolomic data were also generated at 0 h and every 12-24 h thereafter until 120 h of MeJA treatment. Differential gene expression, phylogenetic analysis, and metabolic profiling were used to identify candidate UGTs. Eleven candidate UGTs likely to be involved in ginsenoside glycosylation were identified. Eight of these were considered novel UGTs, newly identified in this study, and three were matched to previously characterized UGTs in P. ginseng. Phylogenetic analysis further asserted their association with ginsenoside biosynthesis. Additionally, metabolomic analysis revealed that the newly identified UGTs might be involved in the elongation of glycosyl chains of ginsenosides, especially of protopanaxadiol (PPD)-type ginsenosides.