Cytotoxic Activity of Dihydrochalcones Isolated from Corema Album Leaves Against HT-29 Colon Cancer Cells

During our search for cytotoxic compounds from Andalusian vascular plants, the ethyl acetate extract from the leaves of Corema album (L.) D. Don (Ericaceae) was selected for its cytotoxic activity against the HT-29 human colon adenocarcinoma cell line. Two dihydrochalcones, 2',4'-dihydroxydihydrochalcone (1) and 2'-methoxy-4'-hydroxydihydrochalcone (2), have been isolated from the leaves of C. album. Their structural identification was based on 1H NMR and 13C NMR data, including 2D NMR, and mass spectrometry. These compounds were subjected to the sulfhorhodamine B (SRB) cytotoxic assay against human colon adenocarcinoma cells (HT-29). Compounds 1 and 2 showed higher cytotoxicity than the positive control 5-fluorouracil (5-FU); the IC50 values (microM +/- SEM) were 1.8 +/- 0.4 for compound 1, 8.5 +/- 2.1 microM for compound 2, and 8.7 +/- 4.0 for 5-FU. The cytotoxic activity of 1 and 2 was reduced in the presence of the antioxidants N-acetylcysteine (NAC) and Mn(III) Tetrakis(1-methyl-4-pyridyl) porphyrin pentachloride (MnTMPyP), therefore suggesting that reactive oxygen species generation participates in the cytotoxic activity of these dihydrochalcones.