Quality control methods for

Histochemical detection of cell walls and contents 
Reagents can be applied to a powdered sample or a section on a slide by the 
following methods: 
• Add drops of the reagent to the sample and apply a cover-glass, then 
irrigate using a strip of filter-paper as described below. 
• Place drops of the reagent on one edge of the cover-glass of a prepared 
specimen. Place a strip of filter-paper at the opposite edge of the cover-
glass to remove the fluid under the cover-glass by suction, causing the 
reagent to flow over the specimen. 
Using the second method, the progress of the reaction may be observed under a 
microscope. Care should be taken to avoid using reagents or vapours that could 
attack the lenses or stages of the microscope. 
Cellulose cell walls 
Add 1-2 drops of iodinated zinc chloride TS and allow to stand for a few 
minutes; alternatively, add 1 drop of iodine (0.1 mol/l) VS, allow to stand for 1 
minute, remove excess reagent with a strip of filter-paper and add 1 drop of 
sulfuric acid (∼1160g/l) TS; cellulose cell walls are stained blue to blue-violet. On 
the addition of 1-2 drops of cuoxam TS, the cellulose cell walls will swell and 
gradually dissolve. 
Lignified cell walls 
Moisten the powder or section on a slide with a small volume of phloroglucinol 
TS and allow to stand for about 2 minutes or until almost dry. Add 1 drop of 
hydrochloric acid (∼420 g/l) TS and apply a cover-glass; lignified cell walls are 
stained pink to cherry red. 

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Quality control methods for medicinal plant materials 
Suberized or cuticular cell walls 
Add 1-2 drops of sudan red TS and allow to stand for a few minutes or warm 
gently; suberized or cuticular cell walls are stained orange-red or red. 
Aleurone grains 
Add a few drops of iodine/ethanol TS; the aleurone grains will turn yellowish 
brown to brown. Then add a few drops of ethanolic trinitrophenol TS; the grains 
will turn yellow. Add about 1 ml of mercuric nitrate TS and allow to dissolve; 
the colour of the solution turns brick red. If the specimen is oily, render it fat-free 
by immersing and washing it in an appropriate solvent before carrying out the 
test. 
Calcium carbonate 
Crystals or deposits of calcium carbonate dissolve slowly with effervescence 
when acetic acid (∼60g/l) TS or hydrochloric acid (∼70g/l) TS is added. 
Calcium oxalate 
Crystals of calcium oxalate are insoluble in acetic acid (∼60g/l) TS but dissolve 
in hydrochloric acid (∼70g/l) TS without effervescence (if applied by irrigation 
the acid should be more concentrated); they also dissolve in sulfuric acid 
(∼350g/l) TS, but needle-shaped crystals of calcium sulfate separate on standing 
after about 10 minutes. In polarized light, calcium oxalate crystals are 
birefringent. Calcium oxalate is best viewed after the sample has been clarified, 
e.g. with chloral hydrate TS. 
Fats, fatty oils, volatile oils and resins 
Add 1-2 drops of sudan red TS and allow to stand for a few minutes or heat 
gently, if necessary. The fatty substances are stained orange-red to red. Irrigate 
the preparation with ethanol (∼750 g/l) TS and heat gently; the volatile oils and 
resins dissolve in the solvent, while fats and fatty oils (except castor oil and 
croton oil) remain intact. 
Hydroxyanthraquinones 
Add 1 drop of potassium hydroxide (∼55 g/l) TS; cells containing 1,8-di-
hydroxyanthraquinones are stained red. 
 
Inulin 
Add 1 drop each of 1-naphthol TS and sulfuric acid (∼1760g/l) TS; spherical 
aggregations of crystals of inulin turn brownish red and dissolve. 
Mucilage 
Add 1 drop of Chinese ink TS to the dry sample; the mucilage shows up as 
transparent, spherically dilated fragments on a black background. Alternatively, 
add 1 drop of thionine TS to the dry sample, allow to stand for about 15 minutes, 
then wash with ethanol (∼188g/l) TS; the mucilage turns violet-red (cellulose 
and lignified cell walls are stained blue and bluish violet respectively). 

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Quality control methods for medicinal plant materials 
Starch 
Add a small volume of iodine (0.02 mol/l) VS; a blue or reddish blue colour is 
produced. Alternatively, add a small volume of glycerol/ethanol TS and 
examine under a microscope with polarized light; birefringence is observed 
giving a Maltese cross effect with the arms of the cross intersecting at the hilum. 
Tannin 
Add 1 drop of ferric chloride (50g/l) TS; it turns bluish black or greenish black.