Separation of indole alkaloids from Aspidosperma rigidum by PH-zone-refining countercurrent chromatography

Species of Aspidosperma genus (Apocynaceae) are, generally, trees found in Central and South America and the teas made from its barks are popularly used by Amazonian “quilombola's” communities to treat several diseases. Although this genus is characterized by the occurrence of indole alkaloids, no recent reports on A. rigidum chemical constituents were found. The present work shows the application of the modern technique of HSCCC in the pH-zone refining mode to the separation of the components present in a dichloromethane extract of the barks from A. rigidum. In this study, the separation of 200mg dichloromethane extract was performed using the solvent system composed by MtBE-water (1:1, v/v) with different concentrations of the retainer triethylamine (TEA) in the organic stationary phase, and of the eluter formic acid or chloridric acid in the aqueous mobile phase. The overall results of our work demonstrated a good separation of the indole alkaloids, including stereoisomers. However, each mode showed to have specific characteristics. Three alkaloids were isolated and identified as 3α-aricine (1), isoreserpiline (2) and 3β-reserpiline (3) in a 2 hours one step fractionation in each experiment. Alkaloids (1) and (2) were identified for the first time in this species.