Rapid Detection of the Active Cardiac Glycoside Convallatoxin of Lily of the Valley Using LOCI Digoxin Assay

Objectives: To explore the luminescent oxygen channeling technology based digoxin immunoassay (LOCI digoxin assay) for rapid detection of lily of the valley extract and convallatoxin. The potential in vitro binding of convallatoxin with Digibind was also evaluated. Methods: Aliquots of a drug-free serum pool and a digoxin serum pool were supplemented with lily of the valley extract or convallatoxin, and then apparent digoxin concentrations were measured using the LOCI digoxin assay Mice were administered lily of the valley extract or 50 fig of convallatoxin, and digoxin concentrations in serum specimens were measured I and 2 hours after gavage. Aliquots of a serum pool supplemented with convallatoxin or lily of the valley extract were further supplemented with various concentrations of Digibind and free apparent digoxin concentrations were measured. Results: Apparent digoxin concentrations were observed when aliquots of a drug-free serum pool were supplemented with convallatoxin or lily of the valley extract, and also with convallatoxin or herbal extract. Bidirectional interference of convallatoxin and lily of the valley extract with serum digoxin measurement using the LOCI assay was also observed. Digibind was capable of binding convallatoxin in vitro. Conclusions: LOCI digoxin assay can be used for rapid detection of convallatoxin, and Digibind can bind convallatoxin in vitro.