Source and Occurrence
Reserpine is extracted from the roots of Rauwolfia serpentina (Indian snakeroot) and Rauwolfia vomitoria.
It is an indole alkaloid with antihypertensive and antipsychotic properties.
Isolation of Reserpine
Extraction:
Alcoholic Extraction: Dried and powdered Rauwolfia roots are extracted with ethanol or methanol to obtain the alkaloids.
Purification:
Acid-Base Extraction:
The extract is acidified to convert reserpine into its water-soluble salt.
Basification liberates the free base, which is then extracted with an organic solvent like chloroform.
Recrystallization: Reserpine is recrystallized from chloroform or ethanol to enhance purity.
Chromatography:
Column Chromatography: Using silica gel and appropriate eluent systems to purify reserpine.
Identification
Physical Properties:
Appearance: Yellowish crystalline powder.
Melting Point: Approximately 190°C.
Solubility: Soluble in alcohol, chloroform; insoluble in water.
Spectroscopic Techniques:
IR Spectroscopy: Identifies functional groups such as indole ring and ester functionalities.
NMR Spectroscopy:
¹H NMR: Reveals proton environments specific to the indole moiety and side chains.
¹³C NMR: Confirms the carbon framework of reserpine.
Mass Spectrometry: Molecular ion peak at m/z 608 (free base).
Chromatographic Techniques:
HPLC: For assessing purity and quantification.
TLC: Monitoring extraction and purification stages.
Analysis
Quantitative Analysis:
HPLC with UV Detection: Primary method for reserpine quantification.
Spectrophotometric Methods: Using specific wavelengths corresponding to reserpine's absorbance.
Quality Control:
Ensuring the absence of other indole alkaloids like ajmalicine.
Verification via spectral data.
Applications and Significance
Reserpine is used as an antihypertensive agent by depleting catecholamines and serotonin from nerve terminals.
It was also employed in psychiatric treatments for its antipsychotic effects, although its use has declined due to side effects.