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INDIAN INSTITUTE OF SCIENTIFIC HERITAGE www.iish.org
THE CHEMISTRY OF KASHAAYA
The kashaayas are the most important class of ayurvedic preparations. In
many cases they are the final formulation. In some cases kashaayas are
intermediate for the preparation of arishta, asava, rasayana, thyla and so
on. Under all these conditions the aim of preparing the kashaaya/ decoction
is to extract very systematically the active principles from the raw drugs.
While preparing the kashaayas, a series of chemical changes known and
unknown will be taking place in the extracts. There is a wrong
understanding that kashaaya preparation is merely extraction of the active
principles present in one or more components of the raw drugs directly.
This wrong understanding has also lead to the direct use of plant extracts
for the preparation of the final formulation. The kashaaya is a decoction
prepared by adopting a series of processing parameters / unit operations.
The quantity of the raw drug components for kashayas is specifically described
in various ways. Either as proportions, weights, lengths, volumes or
arbitrarily selected amounts. Unless otherwise standardized, the use of a
substitutes or extracts may not be as effective as the product obtained by
adopting the method described in the ancient ayurvedic text <strong>book</strong>s .
In the traditional method, the temperature of processing ( heating or warming
)used to be controlled using the specific fuels or sand bath. This method
indicates the temperature control for extraction, concentration, drying,
roasting, etc. In some cases the duration of heat processing has also been
specified directly or by way of reduction in the volume of the solution
Sometimes other additives are also mixed for improving the curative efficacy
of the ayurvedic drugs . Some of the ayurvedic kashayaas are for
purgation, vomiting, or sweating, etc and hence may not have direct curative
effects.
Chemical changes during the preparation of kashaayas.
The raw drug components when heated with water two types of changes are
taking places hydrolytic and pyrolitic changes. The hydrolytic changes
include the conversion of esters into alcohols and acids, rearrangement in the
chemical structure of the components, better dispersion in the water,
removal of the volatile components with steam, imbibitions of the starchy
materials, decomposition of the proteins into peptides, isomerization and
structural changes in the active principles like carotenes, chlorophylls,
vitamins, etc.
In kashaaya preparation, tracing the chemical changes of even the major
components during heating is a complicated problem . A kashaaya is a
multi drug- multi component system . Hence changes can be multi-facial.
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