Chemical diversity and B16F10 inhibitory activity of aerial parts and roots of seven Kalanchoe species: a biochemometric approach toward bioactive substances.

The genus Kalanchoe Adans. is recognized for its medicinal importance and broad pharmacological profile, notably its antitumor activity, often attributed to flavonoids and bufadienolides. This study aimed to establish a comparative chemical profile and investigate the inhibitory potential against B16F10 melanoma cells of aqueous extracts from aerial parts and roots of seven Kalanchoe species - K. delagoensis (KD), K. fedtschenkoi (KF), K. gastonis-bonnieri (KGB), K. × houghtonii (KH), K. laetivirens (KL), K. pinnata (KP), and K. thyrsiflora (KTY) - focusing on the biochemometrics-based identification of bioactive substances. The extracts were cleaned up by RP-18 SPE and characterized by HPLC-DAD and HPLC-MS/MS. Beyond flavonoid glycosides and bufadienolides, this study mapped a diverse array of flavan-3-ols, proanthocyanidins, and gallic acid derivatives in aerial parts and roots. This is the first report of KF, KGB, KH, KL, and KD roots potent toxicity to B16F10 cells. Among aerial parts, only KD showed comparable efficacy. Statistical correlations suggested that gallic acid and galloyl-bound derivatives are the primary contributors to anti-melanoma activity. This was corroborated by the isolation of five bioactive compounds from KD aerial parts: two galloylglucosides-gallic acid 4-O-(6'-O-galloyl)-glucopyranoside (1 - GAGG; IC50: 84.2 μM) and 1,6-di-O-galloylglucopyranose (2 - DGG; IC50: 95.6 μM)-alongside three galloylated flavan-3-ols - epigallocatechin gallate (3 - EGCG; IC50: 26.8 μM), 3'-O-methyl epigallocatechin gallate (4 - MEGCG; IC50: 17.0 μM), and 3',5'-O-dimethylepigallocatechin gallate (5 - DMEGCG; IC50: 12.8 μM). This study provides new insights into the phytochemical profile and bioactivity of Kalanchoe species, with a special emphasis on roots, a plant part understudied.