Chemical structures and corticosterone secretion-inducing activities of saikosaponins.

Abstract

The corticosterone secretion-inducing activities of saikosaponins isolated from the roots of Bupleurum falcatum their artifact saponins and genuine genins were examined in rats 30 min after administration. I.p. administration of saikosaponin-a 1 or -d 2 increased the plasma corticosterone level maximally at a dose of 2.5 mg/kg or 1.0 mg/kg, respectively. Saikosaponin-c did not increase the plasma corticosterone level at a dose of 100 mg/kg. Saikogenin-F and -G, the genuine aglycones of 1 and 2, also increased the plasma corticosterone level but their activities were 1/70-1/90, respectively, of those of the corresponding saponins on a molar basis. Saikosaponin-.beta.1 and -b3, artifact saponins derived from 1 showed 1/8 and 1/40 of the activity of 1, respectively. Saikosaponin-b2 and -b4, derived from 2 through the same structural change as in the case of 1 showed 1/50 and 1/30 of the activity of 2, respectively. Oral administration of 2, which was unstable to acid, increased plasma corticosterone to a maximum level at a dose of 50 mg/kg in fed rats but did not in fasted rats.