PHARMACOLOGICAL PROPERTIES AND IDENTIFICATION OF CARDIOTONIC PRINCIPLES FROM THE INDIAN SNUFF, MAQUIRA-SCLEROPHYLLA, DUCKE

The powdered bark obtained from Maquira sclerophylla Ducke is a snuff used by Amazonian natives. Pharmacological studies on rodents, guinea- pigs, rabbits and dogs revealed cardiovascular changes as the major ef fects produced by the polar phase of the bark ethanol extract, Oriente d by this pharmacological activity a cardenolide fraction was chemical ly purified from the crude extract. Both crude extract and the purifie d fraction produced a positive inotropic effect in isolated heart prep arations from guinea-pigs and rabbits, and inhibited the Na+, K+-ATPas e activity of the enzyme isolated from bovine ventricles. The fraction yielded two major purified cardenolides identified as Maquiroside A ( C30H46O8) and Cymarin (C30H44O9). Simultaneous intracellular recording s of the resting membrane potential (RMP) and miniature endplate poten tials in rat diaphragm muscle fibres showed that the effect of the pur ified fraction predominated on the motor nerve terminals enhancing the spontaneous transmitter release, without major changes of RMP values. Comparatively, the effect of ouabain prevailed on the muscle fibre me mbrane. Considering that both effects depend on the Na+, K+-ATPase act ivity, the results indicated that the compounds derived from Maquira e xert differential actions on this enzyme in the nerve and muscle membr ane. These observations may explain the use of this toxic snuff in nat ive festivities. (C) 1997 by John Wiley & Sons, Ltd.