Antioxidant extracts from 5 potato lines were evaluated for antioxidant activity, total phenolics, chlorogenic acid, anthocyanin content, and in vitro anticancer capacity. Analysis showed that Mexican wild species S. pinnatisectum had the highest antioxidant activity, total phenolic, and chlorogenic acid content. The proliferation of colon cancer and liver cancer cells was significantly inhibited by potato antioxidant extracts. The highest antiproliferative activity was observed in extracts of S. pinnatisectum and the lowest in Northstar. An inverse correlation was found between total phenolics and the EC(50) of colon cancer cell (R(2) = 0.9303), as well as liver cancer cell proliferation (R(2) = 0.8992). The relationship between antioxidant activity and EC(50) of colon cancer/liver cancer cell proliferation was significant (R(2) = 0.8144; R(2) = 0.956, respectively). A significant difference in inhibition of cancer cells (P < 0.01) existed between the 3 polyphenols: chlorogenic acid, pelargonidin chloride, and malvidin chloride, suggesting that chlorogenic acid was a critical factor in the antiproliferation of colon cancer and liver cancer cells.