Page 64 - phytochemistry II -pharmD general

The equatorial N-oxide of hyoscine was isolated from all parts of the latter
two species and from the leaves of belladonna. The proportion of N-oxides to
tertiary base varied among the organs and with different stages of plant
development.

Separation of a mixture of atropine, hyoscyamine and hyoscine

1 Separation of hyoscine from both atropine and hyoscyamine depends on the
difference in their basicity. Hyoscine is a weaker base. The mixture is, thus,
treated with NaHCO3 to liberate hyoscine which can be extracted with ether.
2 Separation of atropine from hyoscyamine is based on the difference in the
solubility of their oxalates in a mixture of acetone and ether and is carried as
follows:
a- The aqueous solution remaining after extraction of hyoscine is rendered

alkaline with ammonia and extracted with chloroform. The solvent is then
evaporated and the residue is dissolved in oxalic acid.
b- Extract with acetone-ether mixture, to separate atropine (sparingly soluble)
from hyoscyamine (freely soluble).
Determination of atropine, hyoscyamine and hyoscine in a mixture

1 The percentage of the total alkaloids (A) is determined by the normal
volumetric method
2 The residue of crude alkaloids obtained after extraction and purification is
taken up by dilute hydrochloric acid.
3 Sodium bicarbonate is added and hyoscine (scopolamine) is extracted with
ether (being a weaker base than atropine and hyoscyamine, it can liberated
from its salt by NaHCO3)
4 The solvent is removed and the residue is dissolved in neutral alcohol and
titrated against standard acid. Then the percentage of hyoscine (B) is
calculated.
5 The aqueous layer remaining after separation of hyoscine is rendered
alkaline with NaOH, then extracted with CHC13, and the solvent is evaporated.
6 The residue is dissolved in 90% alcohol and the optical rotation of the
alcoholic solution is measured from which the percentage of hyoscyamine (C)
can be calculated (Atropine is optically inactive).
7 The percentage of Atropine is calculated by difference as follows:

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