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
Standard alpha-2 adrenergic antagonist
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.
Biological Activity
Rauwolscine hydrochloride is a standard α2-adrenergic antagonist (Ki values are 3.5, 4.6, and 0.6 nM at cloned human α2A, α2B, and α2C-adrenoceptors respectively). Partial agonist at 5-HT1A receptors. Also available as part of the α2-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)
