Introduction: Ellagic acid, a natural phenol with valuable pharmacological activities, is frequently found in fruits, vegetables and nuts. Urolithins are main ellagic acid metabolites that induce chemopreventive and anticancer effects in vitro and in vivo. Colon cancer is among the five most common malignancies in the world. Great efforts have been undertaken to introduce novel and more effective compounds against aggressive colon cancer cells. In the present study, we evaluated and compared effects of urolithins A, B and the methylated form of urolithin A (UA,UB, mUA, respectively) on human colon cancer cells. Methods: After UA, UB and mUA were synthesized, HT-29 cells, a human colon cancer cell line, were treated with increasing concentrations of these three agents for four consecutive days. To note, 0.4% DMSO was used as control treatment. For viability assessment of cells, alamar blue was used and optical density of cells was detected at 600 nm. Results and conclusion: Determination of cell viability 96 h after administration of 10 µM UA, UB and mUA indicated that 69%, 91% and 100% of cells were alive, respectively. Regarding 20 µM concentration, viability of cells was calculated as 72%, 85% and 98% for UA, UB and mUA, respectively. In addition, upon 96 h treatment with 40 µM UA, UB and mUA, cell viability were as 72%, 60% and 96%, respectively. The highest cytotoxic effects were observed 4 days after treatment with 80 µM UA, UB and mUA, as cell viability was dramatically decreased down to 56%, 50% and 67%, respectively. To sum up, current findings revealed that in concentrations < 80 µM, UA induced more toxic effects in comparison with other ellagic acid derivatives, although more research is required to confirm our results on other colon cancer cell lines.

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