Polyphenol rich extracts obtained from cistus herb (Cistus incanus L.) and pomegranate peel (Punica granatum L.) exhibited significant antioxidant activity in V79 cell culture (Chinese hamster lung fibroblasts) -cistus extract reduced intracellular content of reactive oxygen species (ROS) by 30-40% and pomegranate extract by 29-36%. In human breast (MCF-7) and colon (LOVO) cancer cell lines cistus and pomegranate extracts decreased cancer cell growth both in drug-sensitive cells by 15-30% and in drug resistant (doxorubicin-resistant; DX) sublines by 5-20%. However, the extracts did not influence on cell growth%f normal hamster fibroblast cultures (V79). The extracts induced apoptosis in the tested cancer cell lines. Significantly higher proapoptotic impact of the extracts was observed in drug-sensitive than in drug-resistant sublines. The results suggest potential usefulness of the tested polyphenol rich extracts in people exposed to oxidative stress. Their potential use as adjuvant therapy of human cancers needs further studies.