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.