In vitro evaluation of the antioxidant activity of calcium fructoborate.

Although increasing evidence shows the nutritional benefits of calcium fructoborate (CF) on animals and humans, its action mechanism has not been clearly identified. The present study aims to investigate the possible antioxidant function of CF. Based on its efficiency in skin wound healing, the authors tested whether CF possesses antioxidant properties on human keratinocytes cultures, in a complete serum-free medium (KMK-2; Sigma). The cells treated with CF (0-450 nmol/culture medium) were exposed to exogenous 100 micromol of hydrogen peroxide to mimic the oxidative stress. The changes in general cell oxidant production evaluated with dihydrorhodamine-123 showed that the intracellular reactive oxygen species (ROS) were markedly reduced by preincubation with CF. The maximum antioxidant activity was noticed at 90 nmol CF. To assess the reactivity of CF on ROS, we analyzed its ability to inhibit the superoxide- dependent auto-oxidation of pyrogallol. The CF inhibited the pyrogallol auto-oxidation depending on time and concentration, which suggests its possible role as a superoxide radical scavenger. Taken together, our results indicate that CF has antioxidant activity, which could have clinical significance in protecting cells from oxidant-induced injury. A hypothetic mechanism for the antioxidant activity of CF is proposed.