Introduction: Polyphenols are secondary plant metabolites that have shown numerous bioactivity features in many researches, such as antioxidant, antimicrobial, antiproliferative activity and protection from UV radiation. They are phytochemicals and formed as phenylalanine derivatives with an aromatic ring or a hydroxyl group. According to the most recent classification system, polyphenols are divided into two main groups: flavonoids and non-flavonoids (phenolic acids, stilbenes and lignans). Polyphenols inhibit tumor proliferation, induce apoptosis, prevent angiogenesis, and have antioxidant properties that prevent DNA oxidation and reduce the risk of cancer. Objective: The aim of this study is to explore the effect that polyphenols isolated from grapes have on the in vitro cell cycle and to determine the extent to which the efficiency of polyphenolic components changes after the treatment of microorganisms that stimulate the degradation of grape pomace. Materials and Methods: In the research the following materials were used: an extract of pure polyphenolic components and extracts of polyphenols formed after the treatment of microorganisms (Phanerochaete chrysosporium (PC) and Trametes gibossa (TG) in the adequate concentrations corresponding to the IC50 values on the human tumor cell line and CaCo-2.The cells were cultivated under standard cultivation conditions (37°C / 5% CO2) in DMEM without the usage of antibiotics. After 48 hours of exposure to the extracts, the method of flow cytometry for cell cycle analysis was applied. Results: Of the three analyzed polyphenolic extracts, the best results in terms of efficiency in stopping the cell cycle of CaCo-2 and SW620 cells were traced in a PP extract that effected all three phases of the cell cycle; G1 and S phase reduction cycle with G2 / M increase. The effect of TG and PC extracts on the cell cycle are lesser than that of the PP extract. The TG extract resulted in an increase in G1 cell portion and G2 / M phase followed by S phase reduction in SW620 cells. PC extraction caused an increase in the G1 phase and reduction of S phase on the same cell line. The effect on the cell cycle of CaCo-2 cells of these two extracts is lower than that of the PP extract. Conclusion: Polyphenolic components cause changes in the cell cycle of SW620 and CaCo-2 tumor cells by stopping it in the G2 / M phase and reducing the S phase proportion. The effect on the G1 phase is different, possibly depending on the composition of polyphenols and cell types.