Evaluation of the chemopreventive effects of Hypericum perforatum L on DMBA-applied rat oral mucosa

[Display omitted] •H. perforatum L. (HP) has in vitro antioxidant activity.•HP does not possess the ability to inhibit carcinogenesis completely.•HP slowed down the process of DMBA-induced oral carcinogenesis.•HP doesn’t perform its chemopreventive effect through antioxidant defense mechanism.•HP may be a potential chemopreventive agent, but further studies are needed. Hypericum perforatum L also known as St. John’s wort is known to have many beneficial properties for the organism including its antioxidant and anticancer activities. It is also known to have shown antiproliferative and cytotoxic effects against various cancer cell lines. The purpose of this study was to investigate the effects of Hypericum perforatum L on 7,12-dimethylbenz(a)anthracene-induced rat oral squamous cell carcinoma model. The in vitro antioxidant properties of Hypericum perforatum L was determined and an extract was prepared. Thirty Wistar male rats were divided randomly into 4 groups (Control group, DMBA group, HP + DMBA group, HP group). The antioxidant defense mechanisms in tissue and blood samples were evaluated biochemically and immunohistochemically, the carcinomatous changes in connective tissue were investigated immunohistochemically and epithelial changes in the tissue samples were evaluated histopathologically. The extract revealed inhibitory effects on some antioxidant enzymes (catalase, glutathione peroxidase). Immunohistochemical evaluations revealed no invasive changes in the connective tissue. Hypericum perforatum L demonstrated chemopreventive effects although it did not prevent carcinomatous changes altogether. Hypericum perforatum L is a promising chemopreventive agent and further studies are needed in order to evaluate the full potential of this plant.