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Summary of Galenicals 

Definition - A standard medicinal preparation (as an extract or tincture) containing usually one or more active constituents  of  a  plant  and  made  by  a  process  that  leaves  the  inert  and  other  undesirable constituents of the plant undissolved. 

Extraction  involves  the  separation  of  medicinally  active  portions  of  plant  or  animal tissues from the inactive or inert components by using selective solvents in standard extraction procedures.  
Source of drugs : (active ingredients) may be plant or animal. 
Plant  source : Emetine  from  Ipecac  root  Reserpine  from  Rauwolfia  Serpentina  root Atropine from Belladonna leaves.
Animal source : Cochineal from insect Coccus cacti

General procedure : Let us take some dried leaves (known as the crude drug) in a container, add water in it. The  active  ingredient  will  come  out  in  the  water.  Here  water,  i.e.  the  solvent  of  extraction  is called  menstruum.  Later  the  water  is  filtered.  The  filtrate  is  known  as  the  extract.  The  damp crude drugs (damp leaves) are called marc. This marc can be expressed i.e., pressed in a chamber to get the residual liquid, which is mixed with the previous extract.  

Types of Extraction Processes : 
  1. Expression
  2. Infusion
  3. Decoction
  4. Digestion
  5. Maceration
  6. Percolation
  7. Soxhlet extraction  

Solvent Used in Extraction Processes :  
  1. Water  
  2. Alcohol  

1. Water - A solvent for protein, colouring matter, gums, glycosides, sugars, alkaloidal salts, enzymes and many organic acids and salts. Waxes, fats, fixed oils and most alkaloids are insoluble in water.

Advantages :- 
  • Cheap
  • Has wide solvent action
  • Non-toxic  
  • Non-inflammable  

Disadvantages :- 
  • Dissolves wide range of substances 
  • Helps growth of moulds and bacteria, hence preservative required
  • Causes hydrolysis of many substances
  • Large amount of heat is required to concentrate  

2. Alcohol -  A  solvent  for  alkaloids,  alkaloidal  salts,  glycosides,  volatile  oils  and  resins.  Also dissolves Colouring matter, tannins and many organic acids and salts. Albuminous matter, gums, waxes, fats, fixed oils and sugar are insoluble in alcohol.  

Advantages -:
  • Mould and bacterial cannot grow on more than 20% alcohol
  • It is neutral and compatible with other products
  • Non-toxic
  • Small amount of heat is required
  • Dissolves only selective components  

Disadvantages :-
  • Costly
  • Certain alcohols are used rarely

INFUSION - This  method  is  used  for  those  drugs  are  soft  in  nature.  In  this  process,  drug  is  cut  to suitable size and menstruum is added in teapot or infusion pot for the stated period, usually 15 minutes  with  occasional  stirring  and  finally  filtering  off.  Coffee  pot  or  tea pot  is  the  simplest form  of  apparatus  used  for  preparing  infusion.  The  drug  is  placed  at  the  bottom  of  the  pot. Menstruum is added and is well stirred. Menstruum penetrate the soft tissue of plant & diffuses the active constituents in to menstruum. After the specified time content is strained, marc is not pressed and filtered. The filtrate used as it is without dilution.