Chemical Structures and Corticosterone Secretion-inducing Activities of Saikosaponins

抄録

The corticosterone secretion-inducing activities of saikosaponins isolated from the roots of Bupleurum falcatum L., their artifact saponins and genuine genins were examined in rats 30 minutes after administration. Intraperitoneal administration of saikosaponin-a (1) or -d (2) increased the plasma corticosterone level maximally at a dose of 2.5 mg/kg or 1.0mg/kg, respectively. Saikosaponin-c (9) did not increase the plasma corticosterone level at a dose of 100 mg/kg. Saikogenin-F (3) and -G (4), the genuine aglycones of 1 and 2, also increased the plasma corticosterone level but their activities were 1/70 to 1/90, respectively, of those of the corresponding saponins on a molar basis. Saikosaponin-b₁ (5) and -b₃ (7), artifact saponins derived from 1, showed 1/8 and 1/40 of the activity of 1, respectively. Saikosaponin-b₂ (6) and -b₄ (8), 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.