Milk thistle and olive extract: old substances with a new mission against sun-induced skin damage

Natural antioxidants represent an effective option in the prevention and/or improvement of ultraviolet radiations (UVR)-induced/aggravated skin conditions. UVR cause DNA damage in keratinocytes, directly, in the form of cyclobutane pyrimidine dimers (CPDs), or indirectly, through oxidative stress production. Failure of the repair system can result in genetic mutations primarily responsible for the initiation of NMSCs. The aim of our study was to evaluate the in vitro protective effect of milk thistle and olive purified extracts on cultured keratinocytes after solar simulator irradiations (SSR).

Immortalized keratinocytes were pre-incubated with different concentrations of milk thistle and olive purified extracts, and irradiated with increasing doses of SSR. Thereafter, CPDs and p53 expression were evaluated to assess DNA damage, whereas cellular antioxidants consumption and lipid membranes peroxidation were measured to analyze oxidative stress.

The study substances were well tolerated by cells and displayed good cytoprotective and antioxidant activities, being milk thistle dry extract more effective in limiting the direct DNA damage, and olive extract particularly able to reduce lipid membrane peroxidation and to increase cellular antioxidants.

Both study substances can be defined as safe compounds, showing differential cytoprotective and antioxidant activities and might represent interesting options for NMSCs chemoprevention.