In vitro investigated of anticancer effects of essential oil of origanum onites and its constituent carvacrol in hepatocellular carcinoma HepG2 cells

Essential oil of Origanum onites L. and its phenolic constituent carvacrol were investigated for their cytotoxic, apoptotic and hepatotoxic effects in a human hepatocellular carcinoma (HepG2) cells. Cytotoxic effects of these substances were investigated by WST-1 and neutral red uptake and possible apoptotic effects by acridine orange/ethidium bromide staining. Hepatotoxic effects of the oregano oil and carvacrol were also investigated in the expression level of genes involved in hepatotoxicity pathway using RT-PCR array method. Results showed that the oregano oil and carvacrol was significantly cytotoxic and apoptotic in HepG2 cells. IC50 values of the oil and carvacrol was found 0,009% (v/v) and 500 µM, respectively. After incubation of the cells with the oil and carvacrol, characteristics of apoptotic morphology such as shrinkage, cytoplasmic blebbing and chromatin condensation was observed. RT-PCR array analysis of the genes involved in hepatotoxicity pathway showed that 0,008% (v/v) the oil elevated the expression level of GCLC, HYOU1, MAOB, TXNRD1 genes and diminished the expression level of BHMT, DNAJB11, FABP1, HAO2, HPN, IGFALS, LGR5, MBL2, MCM10, OSTalpha, SERPINA3, SLC2A3, THRSP. 300 µM carvacrol also caused an increase in the expression level of DNAJB11, SKIL, TXNRD1 genes while a decrease in the expression level of ABCB1, CYP1A2, IPO4, RLP13A. Some of affected genes are involved in hepatotoxicity and some of them are involved hepatocarcinogenesis. Majority of genes related with hepatotoxicity were not affected after treatment of the cells with these substances. Expression of nine genes involved in nongenotoxic hepatocarcinogenesis was supressed in cells either treated with the oil or carvacrol. In conclusion, both origano oil and its major constituent carvacrol significantly exhibited cytotoxic and apoptotic activities in hepatocellular carcinoma cells although they were not hepatotoxic. Therefore, we suggest that constituents of Origanum essential oil may have a potential as an anticancer agent at least for treatment of hepatocellular carcinoma.