Potential DNA protective effect of an extract from strawberry fruit (Fragaria x ananassa Duch.) against oxidative stress damage

Strawberry fruit is rich in various bioactive compounds such as anthocyanins, phenolic acids and flavo- noids, and has many health-promoting properties. Due to its chemical composition and biological po- tential, this fruit can be considered as a functional food. In this study, the aqueous extract was prepared by ultrasonic extraction from a freeze-dried fresh strawberry fruit. The content of the polyphenolic compounds was measured spectrophotometrically. The cytotoxic and antioxidant effects of the extract on human cell lines (CAL 27, AGS, Caco-2, and HepG2) were performed using the Neutral Red and DCFH- DA methods, respectively. The DNA protective effect was tested on a plasmid model ΦX174 RF1 DNA using agarose gel electrophoresis. According to the results, strawberry extract contains the most procyanidins (64.35 ± 0.05 mg/100 g) and the least flavonols (3.98 ± 0.01 mg/100 g). It was shown that the recommended daily dose of polyphenols, calculated on 5 L of blood and the average weight of a human, had an antiproliferative effect only on the colorectal adenocarcinoma cell line (Caco-2), while it had no effect on the other cell lines tested, and no effect on the induction of free radicals. Moreover, the biologically active compounds in the extract have a dose-dependent protective effect on DNA and prevent the formation of hydroxyl radicals that would lead to the relaxing of supercoiled DNA. The cytotoxic effect of strawberry may be related to the antiproliferative properties of hydroxycinnamic acids, which are one of the most abundant com- ponents of the extract. The results of this work confirm the potential role of strawberry polyphenols against oxidative stress and represent a good basis for further research.