Untargeted RPLC-UV-Vis-HRMS/MS Profiling of Phenolic Compounds in Naturally Grown Kalanchoe delagoensis Leaves

Kalanchoe delagoensis is a Crassulacean acid metabolism (CAM) succulent plant native to Madagascar that has spread as an aggressive invader across subtropical and Mediterranean regions. Research on this species has focused almost entirely on its cardiotoxic bufadienolides, leaving its phenolic fraction largely unexplored. Here, we profiled the phenolics of dried K. delagoensis leaves by reversed-phase liquid chromatography coupled with UV-Vis detection and electrospray ionisation high-resolution mass spectrometry (RPLC-ESI-HRMS). Two flavonoid diglycosides produced the most intense signals and were tentatively annotated by MS/MS analyses as quercetin and kaempferol deoxyhexoside-pentosides; the former shares the formula and fragmentation of quercetin 3-O-arabinopyranosyl-rhamnopyranoside (QAR), the chemical marker of the congeneric K. pinnata. The remaining MS/MS supported features form a single combinatorial family of flavonol glycosides on kaempferol, quercetin, and myricetin cores decorated with pentose, deoxyhexose, hexose, and hexuronic-acid units. Minor flavonol glycosides and mono- and digalloyl hexoses were also detected, and a malvidin-hexoside was putatively identified as a candidate contributor to the reddish leaf tint of the more sun-exposed leaves, supported by its absorption maximum at 520 nm and characteristic MS/MS spectrum. Folin-reactive compounds reached 47.0 ± 0.8 mg gallic acid equivalents per gram of dry leaf. These results extend the chemistry of K. delagoensis well beyond its bufadienolides, within the limits of a single clonal genotype and a single harvest.