164 
Lecithin. 
(  Am.  Jour.  Pharm. 
X      April,  1914. 
Among  the  best  known  members  of  this  group  are  the  cholesterins 
and  lecithins.  While  the  cholesterins  are  organic  combinations  free 
from  nitrogen  and  phosphorus,  the  lecithins  contain  both  nitrogen 
and  phosphorus.  They  are  grouped  together  as  a  special  class  of 
bodies,  the  so-called  "  phosphatides,"  2  comprising  a  large  number 
of  representatives.  The  phosphatides  are  characterized  by  contain- 
ing one  or  more  molecules  of  phosphoric  acid,  an  alcohol  (for  ex- 
ample glycerin),  one  or  more  fatty  acid  radicles  (for  example 
stearic  or  oleic  acid)  and  one  or  more  nitrogenous  bodies  (such  as 
choline  and  allied  substances).  Lecithin,  or  rather  the  lecithins,  are 
phosphatides  of  this  description.  The  theoretical  formula  of  the 
lecithins  is  as  follows: 
It  is  highly  probable  that  other  substances  containing  nitrogen  and 
allied  to  choline  may  occur  in  natural  lecithin,  but  so  far  choline  alone 
has  been  demonstrated  with  certainty  in  the  decomposition  products 
of  the  lecithins.  The  radicles  of  stearic,  palmitic  and  oleic  acid  (R  in 
the  above  formula)  are  present  in  the  form  of  esters  with  the  glyc- 
erin radicle  in  the  lecithin  molecule.  It  has  not  yet  been  possible 
to  determine  whether  one  molecule  always  contains  either  two  similar 
or  two  different  acid  radicles.    Although  in  the  examination  of 
understood  it  to  mean  those  substances  which  cannot  be  saponified  and  which 
may  be  extracted  from  animal  cells  by  means  of  alcohol  and  ether.  If  their 
non-saponification  be  left  out  of  account,  for  it  applies  to  cholesterin  but  not 
to  lecithin,  the  designation  "  lipoid  "  may  still  be  defined  in  the  terms  of  the 
author  mentioned  above,  for  Overton  considers  it  to  denote  all  those  com- 
ponents of  the  cell  which,  like  fat,  will  dissolve  in  ether,  chloroform  and 
similar  organic  liquids.  Kraus  termed  lipoids  "  noble  fats "  to  distinguish 
them  from  fats. 
2  Lecithin  is  a  mono-amino-mono-phosphatide,  which  denotes  that  still 
more  complex  substances  exist,  e.g.,  di-amino-mono-phosphatides,  mono- 
amino-di-phosphatides,  di-amino-di-phosphatides,  tri-amino-mono-phospha- 
tides,  etc.  These  bodies  have  not  as  yet  been  exhaustively  investigated.  (Com- 
pare Thudichum.) 
It  should  be  noted  that  at  the  end  of  the  original  article  in  Merck's 
Report  a  detailed  list  of  the  literature  is  given,  arranged  according  to  authors. 
/O.R 
C3H6^-0 .  R 
OH-$P=0 
/C2H4-0 
NHCH3)3 
\OH 
