**3. Conclusion**

Phenolic plays an important role in human nutrition and health benefit and chemoprevention is one of the most realistic and promising approaches for the prevention of malignant disorders. The results of this chapter may help to identify the phenolic compounds from natural sources with optimized cytotoxic activity to be tested for the treatment of different types of tumors. Phenolic compounds are incorporated into them and the order of their incorporation efficiency is similar to its cytotoxic activity. The cytotoxic data of phenolic compounds compiled in this chapter and relationships presented here cannot only be useful in chemoprevention to choose the correct source of these compounds containing most active natural polyphenols, considering the individual genetic cancer risks and familial anamnesis but also in the selection of parent compounds to design and synthesize novel chemotherapy drugs starting from the valuable material given to us by the nature.
