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    STUDIA BIOLOGIA - Ediţia nr.1 din 2002  
         
  Articol:   BIOTRANSFORMAREA DIGITOXINEI DE CĂTRE CELULELE DE DIGITALIS LANATA IMOBILIZATE ╬N ALGINAT DE CALCIU.

Autori:  CONSTANTIN DELIU, CORNELIA MUNTEANU-DELIU, CRISTINA BOTA, ADELA HALMAGYI, ANCA BUTIUC-KEUL, ANA COSTE, OTILIA CHEREGI.
 
       
         
  Rezumat:  Biotransformation of Digitoxin by Cells of D i g i t a l i s l a n a t a Immobilised in Calcium Alginate. For biotransformation of digitoxin, two Digitalis lanata cell lines were used: cell line 15 (hormone-dependent) and cell line 78 (habituate, hormone-independent), the cells of which were immobilised in calcium alginate. The digitoxin was dissolved either in dimethylsulphoxide (DMSO) or in methanol and added to the culture media in different concentrations and at different growth stages of the immobilised cells. It was found that in comparison with the viability and growth of cell suspensions the viability of the immobilised cells was affected only to a little extent, but their growth was much slower. The factor that had a strongly negative influence on both viability and growth of the immobilised cells was one of the two solvents, namely the methanol. It was also found that in all experimental variants more than 90% of the digitoxin was converted into purpurea glycoside A (PgA). The rate of conversion was influenced mainly by the cell line. Thus, cell line 78 biotransformed digitoxin into PgA during the first 5 days, but cell line 15 did so only after 10 days. PgA was excreted in the culture medium in proportions ranging from 42 to 75%. It was pointed out as well that, in certain cases, the D. lanata cells are able to catalyse, through their enzyme systems, not only the glucosylation, but also the hydroxylation of digitoxin. Thus, the cell line 15 was able to hydroxylise digitoxin, converting it into gitoxin (in a proportion of about 3% relative to the amount of digitoxin), irrespective of the nature of the solvents used. Contrarily, cell line 78 biotransformed digitoxin into gitoxin (in a proportion of about 5%) only when methanol was the solvent.  
         
     
         
         
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