Effects of Thymol, a Natural Phenolic Compound, on Human Gastric Adenocarcinoma Cells In Vitro

Eray Metin Güler, PhD; Ayse Gunes Bayir, DVM; Huriye Senay Kiziltan, MD; Abdurrahim Kocyigit, MD

Context • Alternative and complementary medicine has gained importance in anticancer treatment, reflecting a movement toward an integrated approach to treating various diseases. Natural products originating from plants can contain biologically active substances. Thymol is a major component of many plants from the family Lamiaceae that are often used for medicinal and culinary purposes in Mediterranean countries. Objective • The purpose of the present study was to investigate thymol’s cytotoxic, genotoxic, apoptotic effects on gastric adenocarcinoma (AGS) cells, including measurement of reactive oxygen species (ROS) and glutathione (GSH) levels at the same time. Design • The research team studied thymol’s anticancer potential in vitro. Setting • The research was conducted at the Laboratory of Biochemistry of the Faculty of Medicine at Bezmialem Vakif University (Istanbul, Turkey). Intervention • Caucasian human AGS cells were exposed to 7 concentrations of thymol—10, 20, 30, 50, 100, 200, and 400 µM—prepared from a stock solution of 600 µM of thymol in dimethyl sulfoxide (DMSO), and after 24 h of incubation, the results were analyzed. The thymol was obtained commercially. The study used a negative control prepared in a concentration of 1:1000 from the stock solution of DMSO. Outcome Measures • Cytotoxicity was determined using (1) the adenosine 5’-triphosphate cell viability assay; (2) the dichloro-dihydro-fluorescein diacetate assay to evaluate the generation of ROS; (3) the luminescence-based, total GSH assay to determine the GSH levels; and (4) the comet assay to study genotoxicity. Apoptotic induction of thymol was detected (5) by acridine orange/ethidium bromide staining and (6) by Western blotting using a value below the half maximal inhibitory concentration (IC50). Results • Thymol showed significant cytotoxic, genotoxic, apoptotic, ROS-generating, and GSH-reducing effects, in a dose-dependent manner (P = .001). A close negative relationship existed between cell viability and the ROS level. Conclusions • After researchers have confirmed thymol’s anticarcinogenic effects in vitro on healthy cell lines and in vivo, it may be found to be a novel and strong therapeutic agent against gastric cancer. The study’s results suggest that thymol may have therapeutic power when developed from natural components of the diet for treatment of the disease.

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