Thymol and Thymus Vulgaris L. activity against UVA- and UVB-induced damage in NCTC 2544 cell line

Many authors focused on the research of natural compounds in order to protect skin from indirect (UVA) and direct (UVB) ultraviolet radiation side effects. The aim of this study to evaluate the protective effect of a dry extract from T. vulgaris L. and of its major synthetic compound thymol (about 60%), against oxidative and genotoxic UVA- and UVB damage. Experiments were reproduced in a low differentiated keratinocytes cell line (NCTC 2544) Cells were pretreated for 1 h, in serum-free medium, with thymol (1 μg/mL) or T. vulgaris L. (1.82 μg/mL) then exposed to different UVA (8-24 J/cm2) or UVB doses (0.016-0.72 J/cm2). Immediately after the UV exposure the intracellular redox status was evaluated by ROS quantification and by LPO. Genotoxic aspects were evaluated 24 h after the end of irradiations using the alkaline comet assay, the micronucleus formation assay and the immunostaining of phosphorylated H2AX histone protein (detected 1 h after the end of UV exposure). Thymol and T. vulgaris L. extract inhibited ROS generation in UVA and UVB-irradiated cells. On the contrary, MDA formation was reduced only in UVA treated cells. Both agents decreased the DNA damage evaluated by the alkaline comet assay, but not in the micronucleus and H2AX tests probably because of the severity of damage (double strands) detected.