Hypotensive and spasmolytic effects of normacusine B from Strychnos atlantica root

• Published in: Phytomedicine (Stuttgart) Vol. 3; no. 1; pp. 45 - 49
• Main Authors: Oliveira, E.J., Medeiros, I.A., Mukherjee, R.
• Format: Journal Article
• Language: English
• Published: Germany Elsevier GmbH 01-05-1996
• Subjects: blood pressure; normacusine B; spasmolytic actions; Strychnos atlantica; blood pressure; normacusine B; Strychnos atlantica; spasmolytic actions
• ISSN: 0944-7113; 1618-095X
• DOI: 10.1016/S0944-7113(96)80009-2

Normacusine B, a tertiary indole alkaloid, was isolated in pure form from the root bark of
Strychnos atlantica Krukoff & Barneby. In conscious unrestrained rats, normacusine B (1 mg/kg) decreased the mean arterial blood pressure (27.6 ± 8.4 mmHg, n = 6), followed by a significant increase in heart rate (115.0 ± 12.7 bpm, n = 6). The alkaloid failed to induce tachycardia directly in isolated perfused rat heart. In isolated rat aortic rings, normacusine B antagonized phenylephrine and serotonin-induced contractions. Schild plot analysis of individual cumulative concentration-response curves was compatible with a competitive type of antagonism against phenylephrine (
pA
2 = 7.05 ± 0.11) and of a non-competitive nature against 5-hydroxytryptamine (apparent
pA
2 = 7.02 ± 0.08). Normacusine B was found inactive against KCl and PGF
2α induced contractions.