Extraction of Digoxin from Fermented Woolly Foxglove Foliage by Percolation

Abstract

The present paper deals with the fermentation of chopped, dried, woolly foxglove foliage, the extraction of secondary glycosides from fermented woolly foxglove foliage by the percolation method and the isolation and purification of digoxin. Optimal process conditions for fermenting the chopped, dried, woolly foxglove foliage, extracting of digoxin from the fermented woolly foxglove foliage by percolation, and further isolating and purifying of digoxin were defined. Under the optimum anaerobic conditions for fermentation of the chopped, dried woolly foxglove foliage at 37 • C, the best yield of digoxin of 99-100% was achieved in 48 h. The optimal conditions for extraction of digoxin by percolation (plant particle size: 7 mm; height of foliage in the percolator: 30 cm; extracting solvent: 10%vol. ethanol-or methanol-water solution, volumetric percolate flow rate: 4 L/h and the percolate residence time in the percolator: 4h) ensured the digoxin extraction degree of 97%. Although ethanol is currently more expensive than methanol, it is recommended as extracting solvent because of its lower toxicity. Therefore, the 10%vol. aqueous ethanol solution was recommended as the extracting solvent for recovering digoxin from the fermented woolly foxglove foliage. By further isolation and purification, a highly pure product fulfilling the requirements prescribed by pharmacopoeias was obtained.