Separation of digoxin by luiquid-luiquid extraction from extracts of foxglove secondary glycosides

Abstract

The present study deals with the extraction of digoxin (Dgx) from chloroform and trichloroethylene extracts of the secondary glycosides of fermented foxglove (Digitalis lanata Ehrh.) foliage by liquid-liquid extraction. The extraction degree (ED) of Dgx achieved by maceration and percolation using 10% vol. aqueous ethanol solutions were higher than 95%. Using trichlorethylene and chloroform, the ED of Dgx of about 100% and 96%, respectively from the liquid ethanolic extracts (macerate or percolate) were achieved by the four-cycle extraction. Fifteen separating funnels were employed for the liquid-liquid extraction. Three different four-component two-phase systems (ethanol:water - chloroform:ethyl acetate, ethanol:water - chloroform:trichloroethylene and ethanol:water - trichloroethylene:ethyl acetate) were tested as an extracting solvent to get the final product having more than 98% of Dgx. The initial amount of the chloroform or trichloroethylene extract in the light phase was varied between 5 and 25 g/L, while the volume ratio of light and heavy phases was in the range of 1:1 to 1:2. The best Dgx yield of 98% was achieved with the system ethanol:water - chloroform:trichloroethylene 35:15:20:30 at the volume ratio of the phases of 1:1.1 and at the initial amount of the extract of 15 g/L. Purity of the separated digoxin was 99.8 %.