RAPID, QUANTITATIVE HPLC ANALYSIS OF ASCLEPIAS-FRUTICOSA L AND DANAUS-PLEXIPPUS L CARDENOLIDES

The cardenolide extracts from latex and aerial parts of Asclepias fruticosa and of Danaus plexippus reared on A. fruticosa or A. curassavica were purified by adsorption chromatography on silica gel. HPLC analysis on a C18 reverse-phase column with an acetonitrile-water gradient as mobile phase, separated 28 compounds with a UV spectrum typical for cardenolides. Afroside and gomphoside (major components), as well as calotropagenin, calotoxin, calotropin, calactin, uscharidin, uscharin, and voruscharin, occurred as single peaks in the profiles of latex and aerial plant parts of A. fruticosa. Calactin and calotropin were the major cardenolides in Danaus plexippus reared on A. fruticosa or A. curassavica. Quantitative data obtained with digitoxin as internal standard showed that 1.3-1.5% of the leaf cardenolides were sequestered by Danaus plexippus in which levels of 70-80-mu-g cardenolide per butterfly were measured. The calotropin from the leaves was almost completely sequestered, and 10-13% of the calactin was stored by the butterfly, assuming that no conversion occurred in larval tissues.