Test for chemical constituents. Types of compounds and specific test.
TANNINS
· Solution of tannin precipitates gelatin, and alkaloids.
· Tannins are precipitated by salts of copper, tin & lead.
· They are precipitated by strong potassium dichromate solution or chromic acid solution.
· They show colour reactions with iron salts. Ferric chloride gives bluish-black or brownish-green colour; potassium ferricyanide with ammonia gives deep red colour.
· Goldbeater’s skin test:
It is a prototype of untanned fresh skin of an animal. This skin is obtained as a membrane from the ox intestine. This membrane is treated with hydrochloric acid, rinsed with distilled water and then placed in tannin solution for 5 minutes. It is followed by washing with distilled water and putting in ferrous sulphate solution. A brown or black colour is developed on the skin due to tannin.
· Tannins are precipitated by 2 % solution of phenazone, the tannin solution being prepared with sodium acid phosphate.
ALKALOIDS
The qualitative pharmacognostical chemical tests used to detect alkaloids are depends upon the alkaloids characters to give precipitates as salts of organic acids or with compounds of heavy metals, like gold, platinum, mercury etc.
The different reagents used are
Mayer’s reagent (It is Potassium mercuric iodide solution)
It gives cream coloured precipitate;
Dragendorff’s reagent (It isPotassium bismuth iodide solution)
It gives reddish brown precipitate; and
Wagner’s reagent (It is Iodine-potassium iodide solution)
Wagner’s reagent yields reddish brown precipitate.
Some alkaloids gives yellow colored precipitates with picric acid called as Hager’s reagent and picrolonic acid. Individual alkaloid gives colour or precipitate with certain specific reagent.
FIXED OIL OR FATS
· Using sodium hydroxide (mix 1ml 1% CuSO4 & 5 drops of the fixed oil or fat. Then add 5 drops of 10% NaOH solution. A clear blue solution is obtained which shows glycerine is present in the sample, the cupric hydroxide formed in the reaction does not precipitate out as it is soluble in glycerine.)
· (b)Using sodium hydrogen sulphate (take 5 drops of the sample in a test tube & add a pinch of sodium hydrogen sulphate. Pungent odour emanates from the tube indicating glycerin is present in the sample.)
The pungent odour is due to the formation of acrolein.
GLYCOSIDES
Anthraquinon
· Born Trager test
· Modified born trager test
Cardiac
· Raymond’s test
· Modified raymonds test (Kiddes reagent test)
· Legal test
· Tollens test
· Keller Killiani test
· Antimony trichloride test
· Liebbermann Burchard test
· Xanthohydral test
VOLATILE OIL
· To the thin section of the drug, add alcoholic solution of sudan III Red colour obtained by globules indicates the presence of volatile oil.
· To the thin section of the drug, add a drop of tincture alkane. Red colour indicates the presence of volatile oil.
