Page 27 - Medicinal Plants_PharmD general

Certain rules and precautions for drying medicinal plants:

1. Leaves are usually dried at moderate temperature (40 – 60 ℃) as
long as the active constituents are not destroyed at elevated
temperatures. Also, they must be dried as quickly as possible to
retain their fresh green colour.

2. Flowers must be dried rapidly at very low temperatures in the shade
or drying chambers to retain their colour.

3. Drying barks depend on the nature of their constituents where sun
drying, shade drying or artificial drying can be adopted.

4. Roots and rhizomes are usually sun dried and the process takes
several weeks.

5. Fruits and seeds are spread on trays and dried in the sun or shade.

Changes to medicinal plants can be encountered on drying, such as:

1. Reduction in size and weight due to loss of moisture.
2. Change in shape and appearance where some drugs shrivel and

shrink when dried and the surface becomes wrinkled or reticulated.
3. Change in texture as fresh organs are generally firm and harden on

drying.
4. Darkening or total change in colour. For example, green tea leaves

change to dark brown, almost black on drying.
5. Change in the natural odour. Digitalis lose its bad odour when dried

while fresh vanilla pods are odourless and acquire fragrant pleasant
odour on drying due to liberation of vanillin.
6. Taste may be alterted as in case of the very bitter gentian that acquire
pleasant taste on drying.
7. Constituents may change due to drying.

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