Steroidal saponins and phenolic constituents of Cestrum auriculatum L'Hér.: UHPLC-MS/MS characterization and comparative bioactivity.

Cestrum auriculatum L'Hér. (Solanaceae), traditionally used in Amazonian medicine, was investigated for its phytochemical profile. Aqueous and 70% ethanolic extracts were analysed by UHPLC-MS/MS, tentatively identifying seven furostane-type steroidal saponins, tropoflavin (7,8-dihydroxyflavone), and glycerolipid derivatives based on accurate mass, fragmentation patterns, and literature comparison. The aqueous extract displayed higher total phenolic content and antioxidant capacity (DPPH and ABTS assays) and was non-toxic in the Artemia salina lethality assay (LC50 > 1000 μg/mL). In contrast, the saponin-enriched ethanolic extract exhibited pronounced cytotoxicity (LC50 = 22.52 ± 5.61 μg/mL) but no α-glucosidase inhibition. Extraction polarity significantly influences metabolite distribution and biological activity. The findings provide the first detailed UHPLC-MS/MS characterisation of this Amazonian species, suggesting that steroidal saponins may be key contributors to cytotoxicity and supporting further investigation of the saponin-rich fraction.