Abstract
As a part of our studies of hepatoprotective drugs, we prepared kaikasaponin I (2), sophoradiol monoglucuronide (SoMG, 3) and sophoradiol (4) from kaikasaponin III (1). We examined the hepatoprotective effects of these analogs, using immunologically-induced liver injury in primary cultured rat hepatocytes and found that compound 1 was more effective than soyasaponin I (1a) while 2 was more effective than 1. On the other hand, 3 was less effective than 2 at 30-200 μM. Further, compound 3 was strongly cytotoxic at 500 μM while 4 exhibited hepatoprotective activity at the same dose, although less potent. When the cytotoxicity toward hepatocytes of these analogs was tested, only 3 was cytotoxic at doses of 200 and 500 μM. This is the first example of an oleanene glucuronide (OG) which is cytotoxic toward hepatocytes. Compound 3 exhibited hepatoprotective activity at 200 μM, while it was also cytotoxic at the same dose without antiserum. Therefore, the hepatoprotective activity of OG represents a balance between a hepatoprotective action and its cytotoxicity toward hepatocytes.
