Application of high-performance liquid chromatography to the separation of cardenolides and the assay of digoxin in Digitalis lanata leaf
High-performance liquid chromatography on microparticulate silica gel has been used for the assay of digoxin in Digitalis lanata leaf. The precision of the determination has been improved by the incorporation of an internal standardisation procedure in the chromatographic evaluation of leaf extracts. Factors affecting the extraction of digoxin from the leaf have been investigated, and it is concluded that maceration of the leaf with aqueous ethanol, followed by a de-acetylation reaction, is necessary to release the full digoxin content.
Retention data for a large number of cardenolides have been determined in order to demonstrate the specificity of the assay method, and a relationship between chemical structure and retention time has been revealed.
Specimen chromatograms are included in order to illustrate the applicability of the chromatographic method to the separation and quantitative evaluation of groups of cardenolides.