Synthesis and Cytotoxic Activity of 2,6-Diarylidenecyclohexanones and their 6-Amino-1,3-dimethyluracil Monoadducts

Purpose: The aim of this study was to synthesize a series of symmetrical 2,6- diarylidenecyclohexanones (1-6) and their 6-amino-1,3-dimethyluracil monoadducts (7-10) to evaluate their cytotoxicity in a panel of cell lines. Secondly, to evaluate the effect of the most potent compound on the cell cycle of HeLa cells. Methods: The 2,6-diarylidenecyclohexanones (1-6) were synthesized by the Claisen-Schmidt condensation using cyclohexanone and the corresponding aromatic aldehyde. Monoadducts (7-10) were obtained relying in a one-pot procedure, involving a 1,4-addition of 6-amino-1,3-dimethyluracil followed by self-condensation. The cytotoxicity assay was performed using the MTT assay. The IC50 value was obtained from the dose-response curve at 48 h of treatment. HeLa cell cycle analysis was performed by flow cytometry using propidium iodide to quantify the DNA content. Results: Four of the synthesized 2,6-diarylidenecyclohexanones displayed moderate cytotoxicity in HeLa, K562, MCF7, SW480 and C33 human cell lines ranging from 15.5 to 63.2 μM. Compound 5 was the most potent in K562 (IC50 15.5 μM), C-33 (IC50 16.6 μM) and HeLa (19.0 μM) cell lines. In contrast, when a 6-amino-1,3-dimethyluracil group was added to the 2,6-diarylidenecyclohexanones, the activity was lost. In addition, we showed that compound 5 produces disruption in the cell cycle of HeLa cells, producing an increment in both the sub-G0/G1 and the G0/G1 phase population with a concomitant decrease in the S phase. Conclusion: Compound 1-3 and 5, which are 2,6-diarylidenecyclohexanone derivatives, are cytotoxic on human cell lines. The formation of monoadducts of 6-amine-1,3-dimethyluracil (7-10) was detrimental for the cytotoxic potency. The appearance of a Sub G0/G1 cell population peak, on HeLa cells treated with compound 5, suggests this compound possibly induces an apoptotic cell death.