Am.  Jour.  Ptaarm. 
June.  1903. 
Commercial  Aloes. 
265 
The  other  body,  which  he  names  iso-barb-aloin,  is  not  decomposed 
into  emodin,  but  is  readily  oxidized,  giving  several  distinctive  color 
reactions,  notably  the  deep  red  color  with  nitric  acid,  and  the 
so-called  Klunge's  reaction  for  Barbadoes  aloes,  which,  according  to 
Leger's  investigations  is  really  a  test  for  iso-barb-aloin. 
It  appears  from  Leger's  investigations  that  barb-aloin  is  not 
readily  separated  from  its  contaminating  iso-barb-aloin  by  any 
known  methods  of  procedure. 
According  to  Leger,  the  various  aloes  on  the  market  have 
approximately  the  following  composition :  Barbadoes  aloes,  5  per 
cent,  of  aloin,  traces  of  iso-barb-aloin;  Curacao  aloes,  10  per  cent, 
aloin,  one-half  iso-barb-aloin ;  Cape  aloes,  5  per  cent,  aloin,  no  iso- 
barb-aloin;  Socotrine  aloes,  4  per  cent,  aloin,  very  little  iso-barb- 
aloin ;  Jafferabad  aloes,  20  per  cent,  aloin,  mostly  iso-barb-aloin. 
Tschirch  and  his  assistants  were  probably  the  first  to  demonstrate 
the  similarity  between  the  cathartic  principle  of  aloes  and  that  of 
such  drugs  as  senna,  frangula,  etc.40 
Oesterle41  in  1900  demonstrated  that  the  emodins  of  aloes  and 
frangula  were  isomeric,  both  having  the  chemical  formula  of  C15H10O- 
corresponding  to  trioxymethyl  anthraquinone. 
Aweng42  has  followed  up  the  work  of  Oesterle  and  reports  that 
he  has  been  able  to  isolate  from  the  water-soluble  portion  of  barb- 
aloin  a  glucoside  having  the  reaction  of  oxyanthraquinone,  and 
being  in  all  respects  analogous  to  the  double  glucoside  he  found  in 
frangula  and  cascara. 
By  boiling  with  hydrochloric  acid  he  obtained  as  a  decomposi- 
tion product  a  compound  analogous  to  the  pseudoemodin  he  had 
previously  obtained  from  frangula. 
Leger43  has  more  recently  taken  up  the  study  of  decomposition 
and  addition  products  to  be  obtained  from  barb-aloin  and  iso-barb- 
aloin,  particularly  their  behavior  to  sodium  dioxide.  From  the 
published  reports  it  would  appear  that  iso-barb-aloin  gives  oxidation 
products  closely  related  if  not  identical  with  those  obtained  from 
barb-aloin. 
Pedersen45  has  investigated  into,  and  has  reported  on,  the  chemical 
composition  of  the  resinous  portion  of  the  different  varieties  of 
aloes.  He  finds  that  the  resins  ol  Natal  and  Cape  aloes  are  com- 
posed largely  of  a  resinotannal  ester  of  paracumaric  acid.  In  the 
case  of  Barbadoes  and  Curacao  aloes  this  resinous  portion  is  a  resi- 
