Preliminary study on antioxidant properties, phenolic contents, and effects of Aesculus hippocastanum (horse chestnut) seed shell extract on in vitro cyclobutane pyrimidine dimer repair

Aim: Human skin exposure to solar UV radiation induces cells to produce reactive oxygen species that directly cause DNA damage via the formation of cyclobutane pyrimidine dimers (CPDs), which are the primary UVB-induced DNA lesions. CPDs are responsible for cell death, mutation, and neoplastic transformation. Aesculus hippocastanum (horse chestnut) seed extract has traditionally been used for venotonic treatments and also as a raw material for cosmetics. This study aimed to characterize the antioxidant properties of the phenolic contents of extracts from A. hippocastanum seed shell and endosperm and to investigate their effects on CPD repair in UVB-exposed human dermal fibroblasts in vitro. Materials and Methods: Crude 60% aqueous ethanol extracts (v/v) were prepared, and their total polyphenol contents, antioxidant activities, and ORAC values were measured by Folin–Ciocalteu, 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical-scavenging capacity, and ORAC assays, respectively. The levels of CPDs induced by UVB irradiation were measured by cell-based immunoassays after 6-h treatment with the extract of A. hippocastanum seed shell at a concentration of 100-μg/ml and 9-h treatment with it at concentrations of 50, 100, and 200- μg/ml. Result: A. hippocastanum seed shell extract had 602 ± 1.6-mg gallic acid equivalent per gram of extract and exhibited 4990 ± 70.9 and 7140 ± 835 μmol Trolox equivalents per gram of extract as DPPH radical-scavenging activity and ORAC value, respectively; these values were comparable to those of extracts from green tea and Mallotus japonicus leaves. However, these values of the seed endosperm extract were relatively low. A 9-h treatment of cells with seed shell extracts at concentrations of 50, 100, and 200-μg/ml after UVB exposure significantly reduced CPD levels compared with those in UVB-exposed cells without treatment. Conclusion: This study indicated that A. hippocastanum seed shell extract possesses a potential to limit the harmful effects of human skin exposure to UVB and that this could be the first step toward identifying novel benefits of this extract.