New cardiac glycosides from Adonis amurensis with potent antitumor activity

Twenty-four cardiac glycosides - including six previously undescribed compounds (1-6) and eighteen known analogues (7-24) - were isolated from the whole herb of Adonis amurensis. Their structures were elucidated through comprehensive spectroscopic analysis (1D/2D NMR, HRMS) and acid hydrolysis. All compounds exhibited potent in vitro cytotoxicity against diverse cancer cell lines, with IC₅₀ values ranging from 0.02 to 2.89 μM. Structure-activity relationship (SAR) studies identified critical structural determinants of potency: C-11 hydroxylation, C-10 substituents, glycosylation at C-3, and oligosaccharide chain length. In vitro, compound 5 induced apoptosis in HCT-116 cells via caspase-3/PARP activation. In vivo, compound 5 (2 mg/kg) significantly (41.5 %) inhibited tumor growth in an HCT-116 xenograft mouse model. Immunofluorescence analysis of tumor tissues revealed decreased Ki67 expression (proliferation) alongside elevated TUNEL, cleaved caspase-3, and BAX levels (apoptosis).