Mass production of minor ginsenosides for the study of their pharmacological effects

Abstract

Ginsenosides, which are isolated from ginseng, have been regarded as the principal constituents re-sponsible for the pharmacological activities. They can be categorized as protopanaxadiol (PPD) type, pro-topanaxatriol (PPT) type, and oleanane saponins, based on the structure of the aglycon, with a dammarane skeleton. The six major ginsenosides ($Rb_1$, $Rb_2$, $R_c$, $R_d$, $R_e$, and $Rg_1$) constitute more than 80% of the total ginsenosides in ginseng root, and minor ginsenosides that are deglycosylated from the major ginsenosides exist in smaller amounts in the ginseng. Emerging evidence has demonstrated that the minor ginsenosides have more profound pharmaceutical activities than the glycosylated major ginsenosides. The production of minor ginsenosides from the major ginsenosides has been accomplished through physiochemical and micro-biological methods. However, various enzymatic methods have been reported thus far for the preparation of minor ginsenosides, as a result of their higher conversion efficiency, fewer by-products, superior environmen-tal protection, and better stereo-specificity. For the mass production of minor ginsenosides from major gin-senosides, tens of ginsenosides-transforming glycoside hydrolases from soil bacteria and putative genes were cloned and characterized for ginsenoside-transforming ability. Among them, 3 $\beta$-glucosidases from Acti-nosynnema mirum (BglAm), Paenibacillus mucilaginosus (BglPm) and Microbacterium sp. Gsoil 167 (Bgl167b)

an α-L-rhamnosidase from Bifidobacterium dentium BD1 (BD890) were characterized. Using recombinant glycoside hydrolases, 100 gram-scale or gram-scale production of ginsenoside $F_2$, $Rh_1$, $Rg_2$, gypenoside LXXV and $Rg_1$ have been achieved from relative abundant ginsenosides mixtures or major gin-senosides. These results suggest that these enzymatic methods could be usefully exploited in the preparation of pharmacologically active minor ginsenosides in the cosmetics, functional food, and pharmaceutical indus-tries.