Drugs Containing Carbohydrates and Derived Products
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Carbohydrates, as the name suggest, were defined as a group of compounds composed of carbon, hydrogen and oxygen in which the latter two elements are in the same proportion as in water and were expressed by a formula (CH2O)n, that is, hydrates of carbon.
Drugs
Containing Carbohydrates and Derived Products
INTRODUCTION
Carbohydrates, as the name suggest, were defined as a group
of compounds composed of carbon, hydrogen and oxygen in which the latter two
elements are in the same proportion as in water and were expressed by a formula
(CH2O)n, that is, hydrates of carbon.
The term ‘carbohydrates’ arose from the mistaken belief that
substances of this kind were hydrates of carbon, because the molecular formula
of many substances could be expressed in the form CX(H2O)Y,
for example, glucose (C6 H12 O6), sucrose (C12
H22 O11), etc. In these examples, the hydrogen and oxygen
are present in the same ratio
as in water. But this definition has certain drawbacks as
given below:
· It should be kept in mind that all
organic compounds containing hydrogen and oxygen in the proportion found in
water are not carbohydrates. For example, formaldehyde HCHO for the present
purpose written as C(H2O); acetic acid CH3COOH written as
C3(H2O)2; and lactic acid CH3CHOHCOOH
written as C3(H2O)3 are not carbohydrates.
· Also, a large number of
carbohydrates such as rhamnose (C6H12O5),
cymarose (C7H14O4), digitoxose (C6H12O4),
etc., are known which do not contain the usual propor-tions of hydrogen to
oxygen.
· Finally, certain carbohydrates are
also known which contain nitrogen or sulphur in addition to carbon, hydro-gen
and oxygen.
From the above discussion, it can be concluded that the
definitions described above are not correct; however, carbohydrates are now
defined chemically as polyhydroxy aldehyde or polyhydroxy ketones or compound
that on hydrolyses produce either of the above.
Carbohydrates are among the first products to arise as a
result of photosynthesis. They constitute a large proportion of the plant
biomass and are responsible, as cellulose, for the rigid cellular framework
and, as starch, for providing an important food reserve. Of special
pharmacognostical importance is the fact that sugars unites with a wide variety
of other compounds to form glycosides and secondary metabolites. Mucilage, as
found in marshmallow root and psyllium seeds, act as water-retaining vehicles,
where as gums and mucilage, which are similar in composition and properties,
are formed in the plant by injury or stress and usually appear as solidified
exudates; both are typically composed of uronic acid and sugar units. The cell
walls of the brown seaweeds and the middle lamellae of higher plant tissues
contain polysaccharides consisting almost entirely of uronic acid components.
Low molecular weight carbohydrates are crystalline, soluble
in water and sweet in taste, for example, glucose, fructose, sucrose, etc. The
high molecular weight carbohydrates (polymers) are amorphous, tasteless and
relatively less soluble in water, for example, starch, cellulose, inulin, etc.
