Antioxidant activity of pulp and peel apples extracts evaluated by bacteriophage and DNA protection methods

Free radicals are endogenous initiators of degenerative processes, as they damage lipids, proteins, and DNA, thus favoring the development of a number of degenerative diseases. Apple contains several classes of dietary phytonutrients with strong antioxidant capacities, such as phenolics, carotenoids, and vitamins, which may protect against free radicals. The aim of this work was to evaluate the antioxidant activity of extracts obtained from flesh and peel of apple cultivars from the Protected Designation of Origin Alcobaça, Portugal - 'Casa Nova', 'Gala', 'Granny Smith', 'Reinette', 'Starking', 'Golden', 'Fuji' and 'Jonagored'. The antioxidant capacity was evaluated by ABTS + method and in vitro biological methods - inhibition of DNA oxidative damage and protective effect of phage P22 oxidation by H2O2. The flesh and peel extracts were obtained by mashing flesh (directly) and peel (1:10 in HCL 0.1%) to obtain a concentrated juice of each part. The results confirm, for all cultivars, that antioxidant activity in the peel is higher than in the pulp, which is a valid argument for the consumption of apple with peel. 'Casa Nova' and 'Reinette' possess higher antioxidant activity in the pulp and 'Starking' revealed the best antioxidant activity in the peel. The lower antioxidant activity of the peel extracts was recorded in cultivars 'Golden Delicious' and 'Granny Smith'. It was found that apple extracts showed no protective action upon oxidation of DNA. However, the results ensure that neither extract has pro-oxidant activity. The evaluation of antioxidant activity by bacteriophage P22 and Salmonella typhimurium system showed that the pulp and peel extracts alone (without oxidant) do not affect phage infection over time, however no antioxidant effect was observed in the presence of the oxidant; some extracts even potentiate the oxidant effect upon the phage. This was probably due to the high content of ascorbic acid that, at low pH, could potentiate the oxidant effect of the H2O2 used as oxidant.