1.1. Apocynaceae Apocynaceae is the tenth largest angiosperm plant family, with ca. 5300 species classified in 378 genera (Endress et al., 2018). The family is of particular importance in natural products research because of the occurrence of multiple medicinally important species and compounds including monoterpenoid indole alkaloids, exemplified by the chemotherapy drugs vincristine and vinblastine from Catharanthus roseus (L.) G.Don (Aslam et al., 2010). The expense and difficulty of deriving these valuable molecules from natural sources has motivated the complete biochemical elucidation of their biosynthetic pathway as a steppingstone to its genetic engineering (Caputi et al., 2018; Qu et al., 2019). The genus Asclepias L. and its specialized herbivores are a model system in chemical ecology and evolution of reciprocal adaptations between plants and herbivores, with a particular focus on cardenolides (Agrawal et al., 2012). Pyrrolizidine alkaloids (PAs) are also implicated in co-evolution between Apocynaceae and one of their specialized herbivore lineages, Lepidoptera subfamily Danainae (milkweed and clearwing butterflies). Evolution of the first gene of the PA biosynthetic pathway, homospermidine synthase (hss), has been elucidated (Livshultz et al., 2018a). Researchers have detected phylogenetic signals in the distribution of all of these compounds and others, including steroidal and phenanthroindolizidine alkaloids and steroidal glycosides, in Apocynaceae (Endress et al., 2018), but knowledge of their taxonomic distribution still lags progress on the phylogeny of the family (Fishbein et al., 2018).

Published as part of Barny, Lea A., Tasca, Julia A., Sanchez, Hugo A., Smith, Chelsea R., Koptur, Suzanne, Livshultz, Tatyana & Minbiole, Kevin P. C., 2021, Chemotaxonomic investigation of Apocynaceae for retronecine-type pyrrolizidine alkaloids using HPLC-MS / MS, pp. 1-15 in Phytochemistry (112662) (112662) 185 on page 2, DOI: 10.1016/j.phytochem.2021.112662, http://zenodo.org/record/8259664