METABOLISM OF GINSENG SAPONINS AND ITS SIGNIFICANCE

 

Kazuo Yamasaki1, Ryoji Kasai1, Hiromichi Matsuura2 and Osamu Tanaka1*

1Graduate School of Biomedical Sciences, Hiroshima University, 734-8551, Japan

2Wakunaga Pharmaceutical Co. Ltd., 739-1195, Japan.  *Deceased

 

Studies of the metabolism of Ginseng saponins have mainly focused on the deglycosylation of gisenosides. However, details on the metabolic pathway after absorption from the digestive tract are not known. We carried out two experiments in vitro and in vivo.

As the basic research, we investigated the reaction of the 20(S)-prtopanaxatriol (1) with rat liver 9000g supernatant (S9) mixture which consists of microsomal and cytosolic fractions.

Incubation of 1 with rat liver S9 fraction at 37 for 1 h afforded unique 20,24-epoxysides (3 and 4). This ocotillol type of epoxides can be derived by peracid oxidation of 1. The similar reaction proceeded with 20(S)-prtopanaxadiol (2) to give the corresponding epoxide (5).

From the urine samples from healthy volunteers taken with Panax notoginseng which contains more than 4% of protopanaxatriol saponins and more than 3 % of protopanaxadiol saponins and no ocotillol saponins, saponin fraction was extracted, and after alkaline hydrolysis, not only 1, but also 3 was detected at 15 h from the administration, and the ratio of 3/1 increased and reached the maximum value up to 2.0 at 50h.

The significance of the ocotillol derivatives is discussed, since the main bioactive saponin in Panax vietnamensis is an ocotillol saponin, majonoside R2, 6-xylosylglucoside of 3.