Cardenolide glycosides from the seeds of Digitalis purpurea exhibit carcinoma-specific cytotoxicity toward renal adenocarcinoma and hepatocellular carcinoma cells

Four cardenolide glycosides, glucodigifucoside (2), 3'-O-acetylglucoevatromonoside (9), digitoxigenin 3-O-β-D-glucopyranosyl-(1 → 4)-β-D-glucopyranosyl-(1 → 4)-3-O-acetyl-β-D-digitoxopyranoside (11), and purpureaglycoside A (12), isolated from the seeds of Digitalis purpurea, exhibited potent cytotoxicity against human renal adenocarcinoma cell line ACHN. These compounds exhibited significantly lower IC50 values against ACHN than that against normal human renal proximal tubule-derived cell line HK-2. In particular, 2 exhibited the most potent and carcinoma-specific cytotoxicity, with a sixfold lower IC50 value against ACHN than that against HK-2. Measurement of cyclin-dependent kinase inhibitor levels revealed that upregulation of p21/Cip1 expression was involved in the carcinoma-specific cytotoxicity of 2. Further, compound 2 also exhibited the carcinoma-specific cytotoxicity toward hepatocellular carcinoma cell line.