Studies on South African cardiac glycosides. I. Isolation of toxic principles of Homeria glauca (W. & E.) N.E. Br. and observations on their chemical and pharmacological properties

Abstract

The main toxic principle (1α, 2α-epoxyscillirosidin, a new bufadienolide cardiac aglycone) was isolated by very mild isolation techniques constantly correlated with semi-quantitative toxicity determinations in guinea-pigs. Extraction from plant material was effected at room temperature by suspending it in acetic acid solution and then extracting with chloroform. The residue was extracted with ethanolic citrate buffer and from this phase the toxic components were re-extracted with chloroform. The final separation was done by column chromatography on silica gel. The main toxic component (MTC) constituted 0,044% by mass of the dried plant material. The presence of several other related toxic components was indicated. Certain physical and chemical characteristics of the MTC were determined. The MTC had a subcutaneous LD₅₀ of 0,194 (0,183 to 0,203) mg/kg for guinea-pigs and 3,6 (2,9 to 4,46) mg/kg for mice. The clinical signs were nervous in nature: in guinea-pigs a generalized curare-like paralysis resulted in death from respiratory failure while in mice a convulsive syndrome was encountered. The MTC had potent local anaesthetic properties.