The identification of Hepatotoxins in Kleingrass and a study of their toxicity

Abstract

Steroidal saponins were isolated from the alcoholic extracts of kleingrass (Panicum coloratum L.). Their aglycones, or sapogenins, were identified as diosgenin and yamogenin using TLC, melting point analysis and ER spectrophotometry. By using spectrophotometric analysis, total content of steroidal sapogenins was found to be in the range of 0.2 to 0.7% on the dry weight basis. The sapogenin content varied with age of kleingrass and soil moisture content. Immature kleingrass had higher sapogenin content than the mature plant. Increase in soil moisture content increased sapogenin content in kleingrass. The hepatogenous photosensitizing effects of crude saponins isolated from Agave lecheguilla (lechuguilla) and those of smilagenin and diosgenin were tested in rats and sheep. The clinical signs of icterus, the presence of birefringent crystals in the liver and the increase of serum gamma glutamyltransferases and bilirubin were used as indices of the hepatotoxic effects of the test compounds. Rats fed crude lechuguilla saponins did not exhibit the signs of hepatogenous photosensitization. Sheep fed crude lechuguilla saponins developed hepatogenous photosensitization with birefringent crystals present in the bile, bile ducts and hepatocytes. Rats fed diosgenin and smilagenin showed icterus with clefts of birefringent crystals present in their livers. One of nine sheep fed diosgenin exhibited icterus and photosensitization with birefringent crystals present in the bile. Three of the nine sheep did not exhibit icterus and photosensitization, but birefringent crystals were found in the bile of these sheep. Serum bilirubin was found to increase significantly in the test animals showing icterus. The activity of gamma glutamyltransferases increased significantly (> 100 unit/l) in four sheep that had birefringent crystals in their livers. The clinical signs, lesions, and biochemical effects produced by diosgenin and smilagenin were found to be similar to those produced by crude lechuguilla saponins. These findings suggest that the sapogenins are the toxic metabolites of saponins in producing hepatotoxic effects.