s  6  8  Analysis  of  Rhamnus  Purshiana.      { ^a^sS™* 
The  proportional  quantity  of  the  resins  I.,  II.  and  III.,  is  indicated 
pretty  nearly  by  the  quantity  of  resin  extract  obtained  as  follows  :  An 
acidulated  alcohol  solution  of  the  bark  was  neutralized  (with  ammonia), 
and  evaporated,  the  residue  dissolved  in  dilute  potassium  hydrate  solu- 
tion, this  solution  precipitated  by  dilute  hydrochloric  acid,  and  the  pre- 
cipitate drained  and  dried  at  gentle  heat,  (The  filtrate  contained  some 
resin,  L,  and  the  precipitate  retained,  of  course,  the  dissolved  substances 
not  washed  out.)  This  crude  resin  extract  (chiefly  bodies  I.,  II.  and 
III. )  was  about  ten  per  cent  of  the  weight  of  the  bark. 
The  substances  numberered  III.  and  IV.  appear  particularly  to  de- 
serve farther  chemical  investigation,  which  I  hope  to  be  able  to  give 
them.  The  chemistry  of  the  rhamnacetz  is  of  decided  interest,  espe- 
cially within  a  few  years  past.  Rhamnus  frangula,  the  European  buck- 
thorn, or  black  alder,  has  been  reported  by  Liebermann  and  Waldstein 
(1876)  to  contain  emodin,  a  well-determined  constituent  of  rhubarb, 
allied  to  chrysophane,  and  chemically  a  derivative  of  anthracene. 
Farther,  the  investigators  just  named  find  it  nearly  or  quite  certain  that 
frangulin  is  capable  of  ready  change'  to  emodin,  by  glucosic  fermenta- 
tion. This  may  be  associated  with  the  well-known  fact  that  the  bark 
of  Rhamnus  frangula  changes  in  therapeutic  properties  by  storing.  It 
has  both  emetic  and  purgative  action  in  the  first  year  after  gathering,  but 
when  two  year's  old,  retains  only  the  purgative  power — one  much  like 
rhubarb — so  that  some  authorities  positively  direct  that  it  be  not  used 
until  two  years  after  gathering.  The  glucosic  fermentation  of  frangu- 
lin into  frangulic  acid  has  been  known  for  some  time,  but  the  like  for- 
mation of  emodin,  a  constituent  of  rhubarb,  seems  a  step  nearer  some 
chemical  explanation  of  the  change  of  medicinal  power  characteristic  of 
the  bark.  The  material  worked  by  Liebermann  and  Waldstein  was  a 
large  quantity  of  residual  extract  of  a  large  quantity  of  frangula  bark 
worked  by  the  manufacturer,  Merck. 
The  chemical  constituents  of  Rhamnus  purshiana,  though  not  deter- 
mined in  this  analysis  to  be,  in  any  compound,  identical  with  constitu- 
ents of  the  rhamnus  frangula,  yet  show  several  similar  reactions,, 
especially  in  the  case  of  "  Brown  Resin,  I."  The  rhamnaceae  very  prob- 
ably contain,  in  different  species,  allied  bodies,  some  of  them  related  to 
others  as  parent  and  product,  but  having  practically  distinct  medicinal 
powers.  These  powers,  of  course,  are  known  only  by  physiological 
and  therapeutic  trial. 
University  of  Michigan,  Feb.  5,  1879. 
