Figure 4: Identification of the interactions among tanshinones (TNs).

(a) Algorithms for calculating the combination index (CI) derived from the median-effect equation. (b) IC50 values of different TN pairs at different combination ratios. TNs included dihydrotanshinone (Dih), tanshinone IIA (IIA) and cryptotanshinone (Cry). (c) The CI values of the three TN combinations at different ratios.