Figure 3: Optimization of the flavonoid combination by feedback system control (FSC) scheme. Feedback system control (FSC) scheme was used to optimize the flavonoid combinations. As trial combinations, the drug combinations of four flavonoids were applied onto pHRE-Luc-transfected fibroblasts. The HRE-mediated transcriptional activity was used as the system readout to calculate the fitness of combinations. Differential evolution (DE) algorithm linked the drug combinations and the system readout as to generate new trial combinations in the next iteration.