CRYPTOLEPIS-SANGUINOLENTA - ANTIMUSCARINIC PROPERTIES OF CRYPTOLEPINE AND THE ALKALOID FRACTION AT M1, M2 AND M3 RECEPTORS

From an ethanol extract of the roots of Cryptolepis sanguinolenta the alkaloid fraction and its main constituent cryptolepine were isolated by partitioning at pH 11 and column chromatography using silica gel and chloroform/methanol as eluent. Cryptolepine was identified mainly by EI-MS and H-1/C-13-NMR spectroscopy. Cryptolepine (3-30 muM) and the alkaloid fraction of Cryptolepis sanguinolenta (3-10 mug/ml) antagonized muscarinic effects at Ml receptors in rabbit vas deferens, M2 receptors in guinea-pig atria, and M3 receptors in guinea-pig ileum. The experiments, using N-methylatropine as reference drug, showed a significant antimuscarinic activity for both cryptolepine and the alkaloid fraction, but no appreciable receptor subtype selectivity (pA2 = 5.00-5.73). Cryptolepine was determined as the antimuscarinic principle of Cryptolepis sanguinolenta. At higher concentrations both materials displayed negative inotropic effects.