Cytotoxic activities of tanshinones against human carcinoma cell lines.

Fifteen tanshinone analogues isolated from the chloroform extract of Danshen roots (Salviae Miltiorrhizae Radix) by chromatographic procedures were tested for their cytotoxic activities against KB, Hela, Colo-205 and Hep-2 carcinoma cell lines. Several of them were effective at concentrations below 1 micrograms/ml concentrations. Tanshinone analogues with either hydroxy substitutions or olefinic feature in ring A demonstrated higher biologic activities. Analysis of structure-activity relationship indicate that the basic requirement for activity is the presence of a furano-o-naphthoquinone in the molecule. Compounds which lack an intact furan ring were found to be inactive. It is suggested that the planar phenanthrene ring of the tanshinones may be essential for interaction with DNA molecule whereas the furano-o-quinone moiety could be responsible for the production of reactive free radicals in the close vicinity of the bases to cause DNA damage.