Graphical display of combination index (CI) when liver cancer cells (HEP3B) are treated with varying concentrations of bromelain (Br), N-acetylcysteine (NAC), and in combination with different chemotherapeutic agents. (A) Shows no synergy at all whilst (B) shows good synergy when 15 or 25 ug/ml bromelain is combined with 2.45 mg/ml NAC. (C) Shows synergy when gemcitabine at higher concentrations are combined with bromelain, NAC or bromelain + NAC. A similar scenario exists for 5-FU (D) whilst doxorubicin at various concentrations can be successfully combined with bromelain, NAC or bromelain + NAC to exert good synergy (E). Absence of synergy is shown when oxaliplatin is combined with Br, NAC or their combinations (F). Cisplatin at certain concentrations shows some synergy when combined with bromelain, NAC or Br + NAC (G). The dotted lines show a CI = 1.0 (additivity), CI<1.0 = synergy, CI>1.0 = sub-additivity.