Isolation and Characterization Procedure for Indole Alkaloids from the Marquesan Plant Rauvolfia Nukuhivensis

A plethora of natural products, mostly secondary metabolites, are isolated and purified from many different organisms, like plants, fungi, algae, marine invertebrates, etc. The extraction procedure is specific to each organism, but some guidelines are usually followed for any purification procedure regarding targeted metabolites, such as alkaloids. Alkaloids are secondary metabolites that contain basic nitrogen in their structures and they are often associated with interesting biological properties especially in pharmacology field. This protocol describes the isolation procedure of indole alkaloids from Rauvolfia nukuhivensis directly from the ethanol extract of the plant material yielding different skeleton-type compounds including non-basic derivatives (ajmaline, sarpagine, macroline and β-carboline). The procedure details the guidelines and the steps to characterize new or known isolated compounds, beginning from the plant collection to the molecule level with the use of spectroscopic techniques (NMR, MS, UV). We detailed the extraction and fractionation procedures followed by the purification of compounds, as well as their physico-chemical characterizations. The procedure is illustrated by the example of the purification of a large array of indole alkaloids from the bark of Rauvolfia nukuhivensis.