Alkaloid diversification in the genus Palicourea (Rubiaceae: Palicoureeae) viewed from a (retro-)biogenetic perspective

The species-rich genus Palicourea (Rubiaceae: Palicoureeae) is source of an intriguing diversity of alkaloids derived from tryptamine and its precursor tryptophan. So far simple tryptamine analogues, polypyrroloindoline, beta-carboline, and, most importantly, monoterpene-indole, i.e., tryptamine-iridoid alkaloids of various structural types including javaniside, alstrostine and strictosidine derivatives have been identified. Here the diverse alkaloids that numerous studies have found in the genus are examined and organized according to their structures and biosynthetic groups. Using a parsimony-based approach that follows the concept of retro-biogenesis usually applied in synthetic chemistry, possible biosynthetic pathways are proposed and important steps and relationships between these alkaloids are highlighted. Understanding alkaloid diversification is of importance in studying the ecological significance and evolution of biosynthetic capabilities of the genus Palicourea, and should stimulate future investigations on the biochemical and genetic background.

Automated summary

The diverse alkaloids found in the genus Palicourea have been examined and organized based on their structures and biosynthetic groups. Potential biosynthetic pathways have been proposed using a parsimony-based approach, highlighting important steps and relationships between these alkaloids. Understanding the diversification of alkaloids is crucial for studying the ecological significance and evolution of biosynthetic capabilities of Palicourea, and can drive future investigations on the biochemical and genetic background.