Page 80 - phytochemistry II -pharmD general

strychnine; so, the seed is assayed for its strychnine content and not for total
alkaloids.

Strychnos nux-vomica Alkaloids

N Strychnine ; R = H

R

Brucine (2,3-Dimethoxystrychnine);

RN

R = OCH3

OO

Properties
Strychnine occurs as colorless rhombic crystals, or white crystalline powder,

m.p. 286-288 ˚C. It is soluble in chloroform and benzene but insoluble in water,
25% ethanol and acetone.

Brucine crystallizes as prisms, m.p. 178oC. It is soluble in alcohol, chloroform
and acetone, but insoluble in water. It is dimethoxy strychnine, and is much less
poisonous.
Isolation of strychnine and brucine

▪ The finely powdered Nux-vomica seeds is mixed with Ca (OH)2.
▪ Water is added to make a paste that is dried at 100 ˚C, then extracted with

chloroform.
▪ The alkaloids are extracted with dilute H2SO4 from the chloroform extract.
▪ The acidic extract is rendered alkaline with NH4OH, the precipitated alkaloids

are filtered, the residue is extracted with 25% ethanol, which dissolves brucine
only (c.f. strychnine that is insoluble in dilute alcohol).
Separation of a mixture of strychnine and brucine

Strychnine can be separated from brucine by one of the following methods:

1. Shaking with acetone, where only brucine will dissolve.

2. Shaking with 25% ethanol, where only brucine will dissolve.

Tests for identification

Strychnine
1- Solution in conc. H2SO4 + crystals of K2Cr2O7 ⎯→ a deep blue violet color.

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