Iboga
alkaloids are a group of
monoterpenoid indole alkaloids with promising and intriguing
biological activities.
Ibogaine is the representative member of the series and has become widely known as a potent atypical
psychedelic with promising effects to treat
substance use disorder. Nowadays, an efficient and scalable enantioselective total synthesis of
ibogaine and related iboga
alkaloids is still lacking, so direct extraction from natural sources or semi-synthetic schemes are the methods of choice to obtain them in a preparative scale. In particular,
ibogaine can be obtained either by a low yielding direct isolation from Tabernanthe iboga or using a semi-synthetic procedure from
voacangine, an iboga
alkaloid occurring in a higher yield in the root bark of Voacanga africana. In this work, we describe an optimized process to obtain
voacangine from V. africana root bark as a precursor of the iboga scaffold. Using a direct
acetone-based extraction procedure (0.5 kg of root bark),
voacangine was isolated in ∼0.8% of root bark dried weight, while the major
alkaloids isolated from the bark were identified as iboga-vobasinyl dimers (∼3.7%) such as
voacamine and voacamidine. Since these
alkaloids contain the
voacangine moiety in their structure, the cleavage of the dimers was further optimized, affording an extra amount of
voacangine in ∼50% isolated molar yield. In this manner, the total amount of
voacangine obtained by application of the whole procedure to the plant material (extraction and dimer cleavage) could almost duplicate the content originally found in the root bark.