Isolation, structure elucidation, and biological evaluation of 15-amido-3-demethoxy-2alpha,3alpha-methylenedioxyerythroculine, a new alkaloid from Hyperbaena valida.

A phytochemical investigation of the leaves of Hyperbaena valida resulted in the isolation and characterization of two erythrina-type alkaloids, 1 and 2, which were found to be antagonists at nicotinic receptors. Compound 1 was assigned as the new 15-amido-3-demethoxy-2alpha,3alpha-methylenedioxyerythroculine and compound 2 as the known 3-demethoxy-2alpha,3alpha-methylenedioxyerythroculine. Antagonism of a 100 microM nicotine response was observed for alkaloid 1 (IC50 value of 94 +/- 8 microM) and alkaloid 2 (IC50 value of 77 +/- 19 microM).