Malouetieae

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, Phytochemistry (112662) 185, pp. 1-15 : 8

2.5. Malouetieae

Eleven species from nine of 13 genera of Malouetieae were sampled. PAs were detected with moderate confidence in Eucorymbia alba Stapf (two samples) and Galactophora schomburgkiana Woodson (one sample) ( Table 2). This is the first report of specialized metabolites from these genera. No PAs were detected in the single sample of Galactophora crassifolia (Müll.Arg.) Woodson analyzed ( Table S2), a species that was previously reported as lacking alkaloids ( daRocha et al., 1982). Evenly massed ions were detected in the PREC 120 (with MCA) scan in one of two samples of Holarrhena curtisii King & Gamble (m/z 284.3, 300.1) ( Table S2). Kibatalia macrophylla (Pierre) Woodson (one of two samples) contained three possible PAs in its PREC 120 (with MCA) mass spectrum, m/z 284.3, 302.4, and 314.0 ( Table S2).

The only previous report of PAs in Malouetieae used the Mattocks’ test ( Mattocks, 1967), a colorimetric assay with absorption at 565 nm, to detect unsaturated PAs in the seeds of Holarrhena pubescens ( Arseculeratne et al., 1981) . In our study, crude extracts of H. pubescens leaves were evaluated for PAs via LC-MS/MS, with no strong evidence of PAs in the PREC scans. In seeds of H. pubescens , two even-massed ions were identified in the PREC 120 scan only, m/z 476.4 and 498.4 ( Table 2). These are considered candidate PAs with low confidence. The specialized metabolites of H. pubescens (syn. H. antidysenterica (L.) Wall. ex A.DC., H. floribunda T.Durand & Schinz ) are well studied, with steroidal alkaloids and glycosides of primary interest for their potential bioactivity ( Kumar et al., 2007; Sinha et al., 2013). Three steroidal amino-glycosides previously reported from H. pubescens (holantosine B, D, and F, MW = 475.3 Da) correspond in mass to one of the ions detected in PREC 120 ( Afendi et al., 2011; Janot et al., 1970). Analysis of standards and/or alternative analytical techniques would be required for absolute identification of the compounds detected here.