Page 23 - Medicinal Plants_PharmD general

III. Drying of medicinal plants

Drying consists of removal of sufficient moisture content from the
plant crude drug, so as to improve its quality and make it resistant to
the growth of microorganisms. Drying partially inhibits enzymatic
reactions. Drying also facilitates grinding of a plant crude drug.
Sometimes, the plant material is sliced and cut into smaller pieces to
enhance drying. When medicinal plant materials are prepared for use in dry
form, the moisture content of the material should be kept as low as possible.
Information on the appropriate moisture content for medicinal plants may
be available from pharmacopoeias or other authoritative monographs.

After collection of plant crude drugs, many of them require specific
processing procedures before drying such as cleaning, grabling,
fermentation decortication, bleaching or curing. Some examples are:

1. Fermentation of turmeric (curcuma) to break down otherwise
indigestible plant materials (pre-digests cellulose-rich plant cell
while also reducing the carbohydrate and sugar content. Fermented
turmuric has higher activity.

2. Decortication of cinnamon bark by removing the outer layers
(cork and cortex) due to lack or existence of low amount of active
constituents in the outer parts and presence of unrequired bitter
constituents in the outer tissue that alter its sweet taste.

3. Curing or fermentation of vanilla pods to release free vanillin and
obtain the desired aroma and flavor.

4. Curing or fermentation of tea leaves to set free soluble caffeine
and oxidize tannins into insoluble products.

5. Bleaching of ginger and nutmeg to get good appearance and
colour, minimize shrinkage and pest attacks, and improvee physical
and chemical quality.

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