Identification, structural properties and chelating capacity of miltipolone as a broad-spectrum inhibitor to cancer cells.

Miltipolone (1) was discovered as a good and broad-spectrum inhibitor against the growth of cancer cells from “Danshen” based on the activity-driven screening of TCMs. The structural features make 1 easily tautomerize between different forms and 1 is linked and stabilized by intermolecular O–H⋯O hydrogen bonds in the crystal structure. The interaction of 1 in ddH2O solution with Co2+, Mn2+, Zn2+, Fe2+ or Fe3+ changed UV absorption values; the chelation of 1 with Fe2+ or Fe3+ also altered the characteristic UV absorption peaks. However, only did Fe2+ reverse 1’s inhibition against the growth of cancer cells; therefore, we concluded that 1 possibly acts as a Fe2+ chelator to conduct its inhibitory activity.