Quality control methods for

Fig. 2. Types of leaf stoma 

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Quality control methods for medicinal plant materials 
the fragments are transparent. Transfer a fragment to a slide and prepare it as 
described earlier, the lower epidermis uppermost, in chloral hydrate TS; place a 
small drop of glycerol/ethanol TS at one side of the cover-glass to prevent the 
material from drying. Examine under a microscope with a 40x objective and a 6x 
eyepiece, equipped with a drawing apparatus. Mark on the drawing paper a 
cross (χ) for each epidermal cell and a circle (o) for each stoma. Calculate the 
stomatal index as follows: 
stomatal index =
S
E
x100
S
+
 
where S = the number of stomata in a given area of leaf 
E= the number of epidermal cells (including trichomes) in the same area
of leaf. 
For each leaf sample, no fewer than ten determinations should be carried out 
and the average index calculated. 
Microsublimation 
Mount a small, square metal plate, about 4 x 4 cm in size, on a square of a 
suitable board from which a central hole, about 1 cm in diameter, has been cut. 
Place a metal ring, about 1 cm in diameter and 8 mm in height, at the centre of 
the metal plate aligned with the hole of the asbestos board. Place about 0.1-0.2g 
of powdered material inside the ring to form an even layer, about 2 mm thick. 
Cover the ring with a clean slide. Heat gently and gradually over a small flame 
of a microburner. Change the slide if a large amount of moisture or sublimate is 
observed. Remove the slide from the ring, set it aside until the sublimate has 
dried and then examine under a microscope without adding any fluid and 
without a cover-glass. Prepare 4-5 slides in this manner. 
A heating stage allows the temperature of sublimation to be recorded. 

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Quality control methods for medicinal plant materials