The anticancer effects of thymol on HepG2 cell line

There is an increasing incidence of liver cancer, which is a hazard for global health. The present study was designed to evaluate possible cytotoxic, genotoxic, apoptotic, oxidant and antioxidant effects of thymol on hepatocellular carcinoma (HepG2) cell line. The cytotoxic effect of thymol on HepG2 cell line was determined by XTT test. We also used the HUVEC cell line to show whether thymol damages healthy cells. Oxidative stress level was determined with Total Oxidant Status (TOS) and Total Antioxidant Status (TAS) measurement kits. Apoptosis of cells was detected in flow cytometry with Annexin V apoptosis kit. Apoptotic gene expressions were analyzed by real-time PCR. Genotoxicity was determined by comet assay, which measures DNA damage. The thymol IC₅₀ dose was found to be 11 μM on HepG2 cell line. This dose had no lethal effect on the healthy HUVEC cell line. While thymol significantly decreased the TOS level, it increased the TAS level significantly in HepG2 cells compared to control. Thymol significantly induced apoptosis in HepG2 cells (apoptosis rate in control group 1%, in thymol group 21%). Thymol did not alter the gene expressions of bax, bcl-2, and casp3, all of which are associated with apoptosis. Statistically significant change in favor of genotoxicity was observed in tail length measurements. Our results suggest that thymol decreases oxidative stress in HepG2 cell line, but it induces apoptosis and genotoxicity.