Figure 3.

The effect of polyphenols on cell cycle. Cell cycle phases with (i) stimulatory proteins: cyclin-Cdk complexes and eukaryote transcription factor (E2F) in blue and (ii) inhibitory proteins: retinoblastoma protein (Rb), p15, p16, p21, p27 and p53 in red; phosphorylation of Rb will release E2F which further stimulates cell cycle progression; p53, the tumor suppressor protein is responsible for stimulation of p21 and p27 expression, two inhibitory proteins of the cyclin-Cdk complexes [103,104,105,106,107,108]. Quercetin, resveratrol, curcumin, genisteins and apigenin arrest the cells in G2/M phase, while resveratrol and genistein in S phase; apigenin inhibits Cyclin A, B-Cdk1 complexes, and stimulate p21 and p27; curcumin, apigenin and resveratrol increase the activity of p53 [100,101,102,109,110,111,112,113]. Blue and red lines indicate stimulation and inhibition, respectively, of the process (for the sake of simplicity only the major proteins involved in cell cycle regulation are shown).