Seven dihydrochalcone compounds were isolated from the leaves of Malus crabapples, cv. "Radiant", and their chemical structures were elucidated by UV, IR, ESI-MS, ¹H-NMR and (13)C-NMR analyses. These compounds, which include trilobatin (A1), phloretin (A2), 3-hydroxyphloretin (A3), phloretin rutinoside (A4), phlorizin (A5), 6''-O-coumaroyl-4'-O-glucopyranosylphloretin (A6), and 3'''-methoxy-6''-O-feruloy-4'-O-glucopyranosyl-phloretin (A7), all belong to the phloretin class and its derivatives. Compounds A6 and A7 are two new rare dihydrochalcone compounds. The results of a MTT cancer cell growth inhibition assay demonstrated that phloretin and these derivatives showed significant positive anticancer activities against several human cancer cell lines, including the A549 human lung cancer cell line, Bel 7402 liver cancer cell line, HepG2 human ileocecal cancer cell line, and HT-29 human colon cancer cell line. A7 had significant effects on all cancer cell lines, suggesting potential applications for phloretin and its derivatives. Adding a methoxyl group to phloretin dramatically increases phloretin's anticancer activity.
Keywords: Malus crabapples; anticancer activity; dihydrochalcone compounds; human cancer cell lines; leaves.