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 ddH(2)O solution with Co(2+), Mn(2+), Zn(2+), Fe(2+) or Fe(3+) changed UV absorption values; the chelation of 1 with Fe(2+) or Fe(3+) also altered the characteristic UV absorption peaks. However, only did Fe(2+) reverse 1's inhibition against the growth of cancer cells; therefore, we concluded that 1 possibly acts as a Fe(2+) chelator to conduct its inhibitory activity.