Am"ju°iyr'i9i9rm'  ^  Stability  of  Digitalis  Leaf  Extracts.  429 
tained  in  the  aqueous  liquor  from  which  the  "  digitoxin  "  has  been 
extracted  with  immiscible  solvents. 
Keller  was  the  first  to  point  out  that  he  could  obtain  heavy  pre- 
cipitates in  the  extracted  fluid  with  tannic  acid  after  having  ex- 
hausted the  ammoniacal  liquor  with  chloroform.  It  is  now  well 
understood  that  the  leaves  contain  a  water  soluble  glucoside  or  mix- 
ture of  glucosides,  and  while  it  is  not  known  how  far  the  precipi- 
tation of  resin  removes  activity  it  is  suspected* that  a  greater  propor- 
tion of  the  activity  of  the  leaf  is  water  soluble  and  not  found  in  the 
"  digitoxin "  shake  out.  This  hypothetical  substance  is  known  as 
"  digitalein." 
Kilaini13  and  Windaus  have  made  some  observations  on  this 
point. 
They  prepared  an  infusion  (15  minutes)  which  was  concentrated  with 
some  loss  of  activity  to  a  syrup.  This  was  diluted  with  strong  alcohol  and 
the  precipitate  filtered  off.  The  concentrated  filtrate  was  dissolved  in  water 
and  precipitated  with  tannic  acid.  The  precipitated  tannates  were  decom- 
posed with  zinc  oxide  and  the  liberated  glucosides  were  dissolved  in  alcohol 
(4  parts).  To  this  two  parts  of  ether  were  added,  and  an  active  precipitate 
obtained  (2  Mg.).  It  weighed  16  Gm.  from  10  Kg.  and  was  water  soluble. 
To  the  main  alcohol -f- ether  solution,  a  further  addition  of  ether  (4  parts) 
gave  a  second  precipitate  which  was  water  soluble  and  active  (1  Mg.).  .The 
final  solution  from  the  ether  precipitations  contained  20  Gm.  of  which  2  Gm. 
was  water  soluble  and  toxic. 
Kiliani  then  took  the  leaves  which  had  already  been  used  to  prepare  the 
infusion  and  extracted  them  with  alcohol.  The  alcohol  was  distilled  off,  and 
the  residue  taken  up  with  absolute  alcohol  and  filtered.  The  alcohol  was 
again  removed  from  the  filtrate  and  the  residue  taken  up  in  water,  and  fil- 
tered from  resin.  This  aqueous  solution  was  extracted  with  ether  and  with 
chloroform.  The  water  soluble  part  (1.5  per  cent.)  was  very  active  (1.5 
Mg.).  The  solution  was  saturated  with  magnesium  sulphate  and  an  active 
substance  (0.6  Mg.)  precipitated. 
While  the  above  work  is  chemically  indefinite  it  is  necessary  to  under- 
stand that  it  is  from  this  work  that  the  term  "  digitalein "  is  derived  and 
that  it  means  the  water  soluble  active  principle  or  principles  of  the  leaf. 
The  work  of  Kraft  also  has  a  bearing  on  the  water  soluble  constituents. 
Kraft  it  will  be  recalled  first  extracted  the  drug  with  cold  water,  and  then 
after  clarifying  with  lead  and  sodium  phosphate,  precipitated  glucosides  with 
tannin.  This  precipitate  contained  chloroform  soluble  material  which  was 
removed  by  extraction  and  also  water  soluble  material  which  Kraft  named 
digitalis  leaf  "saponin."  Contrary  to  Kiliani's  work  on  the  infusion  where 
an  active  "  digitalein "  was  found,  Kraft  found  his  water  soluble  material 
13  Arch.  Pharm.,  237,  464  (1899). 
