To mitigate the UV radiation-induced damage, the skin has efficient defence mechanisms consisting of both antioxidant enzymes (superoxide dismutase, catalase, and glutathione peroxidase) and non-enzymatic antioxidant molecules (vitamin C, vitamin E, glutathione, and ubiquinone). Topical or systemic treatments of skin with products containing antioxidant compounds could be a useful tool to prevent UV-induced cutaneous damages. Many studies have shown the efficacy of some antioxidant molecules naturally occurring in plants against UV radiation-induced inflammation and cancer. In addition, it has been reported that the topical application of plant-derived molecules inhibits cancer and increase apoptosis in UV-B-treated mouse skin.
Strawberry is an important dietary source of bioactive compounds, most of which are naturally antioxidants. It is rich of vitamin C, folate, and phenolic compounds, among which the anthocyanins are the quantitatively most important. Most of 25 different anthocyanins have been described in strawberry fruit from different varieties, among these the most important are pelargonidin and cyanidin. These compounds have strong anti-inflammatory, antimutagenic, anticarcinogenic, and photoprotective properties and are able to modulate enzymatic pathways.
The objectives of the study conducted by Giampieri et al. (2012) were to characterize the strawberry anthocianins content and to evaluate the potential protective effect of strawberry extract on UV-A-induced skin damage using human dermal fibroblasts.
Strawberry cultivar ‘Sveva’, grown at the Azienda Agraria Didattico Sperimentale “P. Rosati” in Agugliano (Ancona, Italy), was used for the work. The samples were prepared for the extraction of anthocianins, and the extract was analysed by HPLC-MS (high performance liquid chromatography- mass spectrometry). Fibroblasts cultures were prepared, and the cells were incubated for 24 h with different concentrations of strawberry extract (0.05; 0.25; 0.50 mg/mL). After incubation, the cells were exposed to the UV-A source for a maximum of 30 minutes because longer exposure times showed a serious loss of cell vitality and DNA damage. For the UV treatment, the source delivered 23mW/cm 2 between 300 and 400 nm at a distance of 20 cm from the cell cultures.
By analyzing the extract profile, five anthocianins were identified: cyaniding-3-glucoside, pelargonidin-3-glucoside, pelargonidin-3-rutinoside, pelargonidin-3-malonylglucoside, pelargonidin-3-acetylglucoside. The extract resulted to be not cytotoxic for the cells, whose vitality did not vary by increasing the strawberry extract concentration or the exposure time to UV-A. The cells pre-incubated with the lower concentration of extract exhibited vitality similar to the control cells, while the cells pre-incubated with the higher concentrations of the extract showed higher survivability. In particular, cells treated with 0.5 mg/mL showed a significant difference in vitality, especially for exposure between 5 and 15 minutes. Ultimately, cells pretreated with 0.25 and 0.5 mg/mL of extract showed a greatly significant decrease in DNA damage compared to the control cells.
The present work has shown the photoprotective effect of strawberry extract on human fibroblasts and has provided the basis for future studies, which will regard the evaluation of bioavailability of the anthocianins at dermal level when these antioxidant molecules are introduced through topical application.
Original study. Giampieri F., Alvarez-Suarez JM., Tulipani S., Gonzales-Paramas AM., Santos-Buelga C., Bompadre S., Quiles JL., Mezzetti B., Battino M., "Photoprotective Potential of Strawberry (Fragaria x ananassa) Extract against UV-A Irradiation Damage on Human Fibroblasts", Journal of Agricultural and Food Chemistry, 2012, Issue No. 60, pagg. 2322-2327.