Chemistry of nux vomica

Nux vomica is derived from the seeds of the plant Strychnos nux-vomica, containing toxic alkaloids such as strychnine and brucine. The seeds are traditionally used in medicine for various purposes, although they are toxic at higher doses. Here's a summary of the chemistry and identification tests for nux vomica:

 

Chemistry of Nux Vomica

1. Alkaloids: The primary active constituents of nux vomica are the alkaloids:

   • Strychnine: A potent central nervous system stimulant that blocks glycine receptors, leading to increased muscle activity.
   • Brucine: Less toxic than strychnine and also found in significant amounts.

2. Chemical Properties:

   • Strychnine is a white crystalline solid that is bitter in taste, while brucine has a similar structure but is slightly more polar.
   • Both are soluble in alcohol, and chloroform, and slightly soluble in water.

Identification Tests for Nux Vomica

Several tests are used to detect the presence of strychnine and brucine in nux vomica:

1. General Alkaloid Test:

   • Dragendorff’s Reagent: A precipitate (usually orange) is formed, indicating the presence of alkaloids.

2. Specific Chemical Tests for Strychnine:

   • HNO₃ Test (Nitric Acid Test):
     • To a small amount of powdered nux vomica, add concentrated nitric acid. A bright yellow color appears, turning to orange-red, indicating the presence of strychnine.
   • Potassium Dichromate Test:
     • Add a few drops of potassium dichromate solution to an acidified sample of strychnine. The mixture gives a greenish coloration, which further confirms the presence of strychnine.
   • Strychnine Fluorescence Test:
     • A small amount of strychnine dissolved in concentrated sulfuric acid, with a trace of potassium dichromate, will show blue fluorescence under UV light.

3. Brucine Tests:

   • Conc. HNO₃ and Ammonia Test:
     • Add a few drops of concentrated nitric acid to brucine, which results in a red color. Upon adding ammonia, the red color changes to purple, indicating brucine.
   • Sulfuric Acid and Bromine Test:
     • Brucine produces a violet color when treated with sulfuric acid and a small amount of bromine water, which is a distinctive reaction.

Identification by Thin-Layer Chromatography (TLC)

• TLC can be used to separate and identify strychnine and brucine.
• A mobile phase such as chloroform and methanol is used, and the spots can be visualized using UV light or by spraying with Dragendorff’s reagent.
• Strychnine and brucine will produce distinct spots with characteristic Rf values.

Spectroscopic Methods

• UV-Visible Spectroscopy: Strychnine and brucine absorb UV light at characteristic wavelengths. This method can be used for quantitative analysis.
• Infrared (IR) Spectroscopy: Provides information on functional groups present in the alkaloids, confirming their identity.

Microscopic Identification of Nux Vomica Seed Powder

• The powder shows characteristic features like lignified stone cells and calcium oxalate crystals.
• Starch grains are also present, which can be stained with iodine to appear blue-black under a microscope.

These tests are critical for the proper identification of nux vomica, especially given the highly toxic nature of its alkaloids, making accurate identification essential for any pharmaceutical or medicinal use.