Biotransformation of Ginsenoside Rd into 20(S)-Rg3 by Bacterium Flavobacterium sp. BGS36

Abstract

Triterpenoid glycosides, i.e., ginsenosides, are the main active principles of Panax ginseng C. A. Meyer and are responsible to the various pharmacological properties of this unique plant [1]. One of the most active minor constituents of P. ginseng is ginsenoside 20(S)-Rg3, which possesses a broad spectrum of biological activity, in particular, growth inhibition of malignant A549 lung cancer cells, U937 lymphoma, LNCaP prostate carcinoma, and SK-HEP-1 hepatoma. It is viewed as a potential anticancer drug among P. ginseng saponins [2]. 20(S)-Rg3 differs from the principal ginseng glycosides Rb1, Rb2, Rc, and Rd, which have protopanaxadiol as the aglycon, only by the lack of a carbohydrate group on C-20 [1]. This enables it to be prepared by selective incomplete deglycosylation of these saponins, including the use of various microorganisms [3]. We communicated earlier the isolation from soil samples taken from a ginseng field of several bacteria with -glucosidase activity [4] and the use of several of them to convert ginsenosides Rb1 into Rd [5] and Rd into the minor glycoside F-2 and compound K [6]. In continuation of these studies, we present data on the biotransformation of Rd (1), which has -sophorose and -D-glucose residues in the C-3 and C-20 positions, respectively, of 20(S)-protopanaxadiol, into ginsenoside 20(S)-Rg3 (2) using the bacterium Flavobacterium sp. BGS36.