Protective effect of kava constituents in an in vitro model of oral mucositis

Purpose: Oral mucositis is a debilitating inflammatory disorder observed in patients undergoing active cancer treatment, particularly cancer of the head and neck region. A key pathway believed to be involved in the pathogenesis of oral mucositis is the formation of reactive oxygen species (ROS). The identification of compounds that can inhibit this pathway may therefore be of benefit in treating this disorder. The kava plant (Piper methysticum) contains various constituents, including flavokawain A (FKA), flavokawain B (FKB), yangonin, methysticin and kavain. These constituents are known to be biologically active and possess anti-oxidative properties. This study therefore focused on examining these constituents for their effect on ROS formation in an in vitro oral mucositis model.

Methods: Cell proliferation was assessed in normal oral keratinocytes (OKF6) treated with and without kava constituents, namely FKA, FKB, yangonin, methysticin and kavain using an MTS in vitro assay. Oxidative stress was assessed by co-treating and pre-treating OKF6 cells with H₂O₂. The effects were quantified by analysis of ROS production, using a CM-H2DCFDA assay.

Results: Pre-treatment of cells for 24 h with 2.5 μg/ml kavain and 5 μg/ml FKA demonstrated a significant protective anti-oxidative effect. Similarly, FKB at a concentration of 2.5 μg/ml, demonstrated a trend of ROS reduction but was observed to be cytotoxic at concentrations greater than 5 μg/ml. Reduction in ROS production by methysticin and yangonin was compromised by their cell cytotoxicity.

Conclusion: This was the first study to identify the anti-oxidative effects and safety of FKA and kavain with regard to oral keratinocytes, highlighting their potential use in the development of a preventative treatment for oral mucositis.

Keywords: Flavokavain; Flavokawain; Kava; Kavain; Oral mucositis; Piper methysticum.