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.