Cardenolide genin pattern in Isoplexis plants and shoot cultures.

An HPLC method for the quantitative analysis of cardenolides was developed and applied. The procedure was optimised for analysing small samples (40 mg dw) of plant and tissue culture material. ISOPLEXIS CANARIENSIS plants obtained from seeds accumulated cardenolides to about 20 - 40 micromol g (-1) dw as calculated from the levels of cardenolide genins released after acidic hydrolysis of methanolic extracts. The relative contents of xysmalogenin, digitoxigenin, uzarigenin and canarigenin were 5 - 15 %, 0 - 5 %, 10 - 15 % and 70 - 90 %, respectively. Shoot cultures were initiated from seeds, established as permanent cultures and cultivated on agar-solidified or in liquid medium. Shoot cultures maintained on solid medium contained an average of about 6 micromol cardenolides g (-1) dw. A relatively high proportion of digitoxigenin was found in two-thirds of the shoot cultures examined. The cardenolide content of amphibian shoot cultures averaged to about 1 micromol g (-1) dw. Plants regenerated from shoot cultures and maintained under hydroponic conditions accumulated the same amount of cardenolides as plants collected in the field. No cardenolides could be detected in callus cultures.