a D₁/D₂ Dopaminergic receptors antagonist presenting analgesic and sedative/tranquillizing effects; voltage dependent Ca²⁺ channel blocker; antiarrhythmic and hypotensive.

Stephania glabra diisoquinoline alkaloid C₂₁H₂₅NO₄.HCl synthetic

• Molecular Weight : 391.7 Da.
  
  
• Melting Point : 250-252 °C.
  
  
• Solubility in : water.
  
  
• Purity min. : 95% (TLC, mass-spectrometry).
  
  
• Biological Activity : Tetrahydropalmatine presents a sedative/tranquillizing effect, probably due to its antagonistic action on D₁/D₂ receptors in brain (Vauquelin et al., 1989). The effect of Tetrahydropalmatine on the left auricle of the guinea pig is similar to that of verapamil and antagonistic to calcium. Tetrahydropalmatine mainly inhibits voltage-dependent Ca²⁺ channels [5]; 6-12 mg/kg (i.v.), 30 mg/kg (i.p.) and 60 mg/kg (s.c.) suppress arrhythmia caused by Strophanthin, Aconitine and CaCl2 (Yu-Wan et al., 1987).
  
  
• Toxicity (LD₅₀) : mice (orally): 1 160 mg/kg. rats (orally): 930 mg/kg. mice (s.c.): 670 mg/kg.
  
  
• Storage recommendations : Store at +4°C, in dark place.
  
  
• CAS Reg. No. : 6024-85-7
  
  
• Merck Index 11th Ed. : 6945
  
  
• Bibliography :
  
  1. Vauquelin et al., "(+-) tetrahydroanisocycline and (+-) tetrahydropalmatine binding to D1 and D2 Dopaminergic receptors in human putamen". Neurochem. Int. (1989) 15(3):321-324
  2. Marcenac et al. "Effect of l-tetrahydropalmatine on dopamine release and metabolism in the rat striatum." Psychopharmacology (1989). 89:89-93
  3. Chen et al. "Calcium antagonists from traditional Chinese herbs." Drug News and Perspectives (1990). 3(7):425-428
  4. Zhao et al. "Effects of dl-Tetrahydropalmatine on contractions of rabbit aortic strips." Acta Pharmacologica Sinica (Chinese; abstract in English) (1988). 9(2):153-155