Received for review December 8, 2006. Revised manuscript received March 26, 2007. Accepted March 27, 2007. This work was supported in part by No. 06A127 from the American Institute for Cancer Research and the Ngan Foundation.

Abstract:

Bioactivity-guided fractionation of apple peels was used to determine the chemical identity of bioactive constituents. Thirteen triterpenoids were isolated, and their chemical structures were identified. Antiproliferative activities of the triterpenoids against human HepG2 liver cancer cells, MCF-7 breast cancer cells, and Caco-2 colon cancer cells were evaluated. Most of the triterpenoids showed high potential anticancer activities against the three human cancer cell lines. Among the compounds isolated, 2-hydroxyursolic acid, 2-hydroxy-3-{[(2E)-3-phenyl-1-oxo-2-propenyl]oxy}olean-12-en-28-oic acid, and 3-trans-p-coumaroyloxy-2-hydroxyolean-12-en-28-oic acid showed higher antiproliferative activity toward HepG2 cancer cells. Ursolic acid, 2-hydroxyursolic acid, and 3-trans-p-coumaroyloxy-2-hydroxyolean-12-en-28-oic acid exhibited higher antiproliferative activity against MCF-7 cancer cells. All triterpenoids tested showed antiproliferative activity against Caco-2 cancer cells, especially 2-hydroxyursolic acid, maslinic acid, 2-hydroxy-3-{[(2E)-3-phenyl-1-oxo-2-propenyl]oxy}olean-12-en-28-oic acid, and 3-trans-p-coumaroyloxy-2-hydroxyolean-12-en-28-oic acid, which displayed much higher antiproliferative activities. These results showed the triterpenoids isolated from apple peels have potent antiproliferative activity and may be partially responsible for the anticancer activities of whole apples.

Keywords: Apple; apple peels; phytochemicals; phenolics; triterpenoids; breast cancer; antiproliferative activities; MCF-7 cells; cancer cells

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