Purification and Separation of Digoxin by Removal of Accompanying Glycosides as Phenylboronate Derivatives

Abstract

A new process has been developed for the purification and separation of digoxin from accompanying glycosides, utilizing their common feature of containing 1 , 3 4 0 1 units in their skeletons which can form cyclic esters with phenylboronic acid. As the polarity of the glycoside phenylboronates is substantially different from that of digoxin, they can be Separated easily.lntroduction Digoxin (Fig. I), a glycoside of greatest therapeutic importance as a cardiotonic, is isolated from the leaves of Digitalis lanata EHRH. The living plant contains the lanatosides predominantly in their primary form of aglycone-(digitoxose) 2-acetyldigitoxose-glucose [I]. In the Course of processing the plant, glucose is split off by the digilanidase enzyme and the acetyl group is hydrolyzed by the acetylase enzyme in the plant. As a result the drug also contains secondary glycosides of the type sttucture aglycone-(digitoxose), : digitoxin, digoxin, gitoxin and diginatin (Fig. I), as well as other glycosides present in minor quantities. The plant can also be processed in such a way that all glycosides are hydrolysed into their secondary forms.Digoxin may also be prepared by the microbial hydroxylation of digitoxin.In the Course of digitoxin transformation with microorganisms known to be able to hydroxylate in position 12ß, glycosides hydroxylated in position 7 ß are also formed as by-products: 7 P-hydroxydigitoxin and 7 P-hydroxydigoxin [2, 31.M. NATONEK et al. [3] hydroxylated digitoxin to digoxin as a main product using Streptomyces praecox strain MNG-127. The bioconversion was carried out at a substrate concentration of 500 pg digitoxin per millilitre broth. After a four day fermentation the digitoxin was transformed to digoxin with a conversion of Heruntergeladen von: University of British Columbia. Urheberrechtlich geschützt.