Description
This alkaloid is isolated as the oxalate from the leaf extract of Rauwolfia
canescens L. from which the free base may be obtained as colourless needles
which are laevorotatory with [α]30D - 40° (EtOH). The alkaloid forms crystalline
salts: the hydrochloride, m.p. 27S-2S00C (dec.); [α]30D + 74° (H20); nitrate,
m.p. 257-SoC (dec.); oxalate, m.p. 245-6°C and the picrate, m.p. 20SoC. Two
active hydrogens are present and the alkaloid furnishes a monoacetyl derivative,
m.p. 2l6-SoC (dec.). Treatment with concentrated ammonia solution at room
temperature converts the base into rauwolscinic acid, C2oH2403N2.H20, m.p.
262-4°C (dec.); [α]23D + l36.So (H20) which yields a crystalline hydrochloride,
m.p. 255.5-257.5°C (dec.) and on esterification with MeOH reverts to the
original alkaloid. On distillation with Zn dust, rauwolscine yields harman,
2-methylindole (skatole) and isoquinoline.
Chakravarti has shown that the alkaloid is a cardiovascular depressant, shows
hypotensive activity and is relatively highly toxic.
Uses
Rauwolscine is a natural alkaloid that acts as a selective and reversible α2-adrenergic receptor antagonist (Ki = 12 nM). It is a stereoisomer of yohimbine, which potently antagonizes both α1- and α2-adrenergic receptors. Rauwolscine also acts as a receptor antagonist at the serotonin 5-HT2B receptor (Ki = 14.3 nM) and as a weak partial agonist at 5-HT1A (IC50 = 1.3 μM).The α2-adrenergic receptor has diverse physiological functions and antagonists like rauwolscine have numerous applications, including the modulation of mood and behavior.
Uses
Standard alpha-2 adrenergic antagonist
Biological Activity
Standard α 2 -adrenergic antagonist (K i values are 3.5, 4.6 , and 0.6 nM at cloned human α 2A , α 2B , and α 2C -adrenoceptors respectively). Partial agonist at 5-HT 1A receptors. Also available as part of the α 2 -Adrenoceptor Tocriset™ .
References
Mukherjee., J. Ind. Chern. Soc., 18, 33, 485 (1941)
Mukherjee., ibid, 20, 11 (1943)
Mukherjee., ibid, 23, 6 (1946)
Pharmacology:
Chakravarti., Sci. Cult., (Calcutta), 7, 45S (1942)
