Evaluation and characterization of antioxidant and antigenotoxic properties of portuguese propolis

Abstract

Propolis is a substance produced by bees (Apis mellifera L.), after harvesting exsudates of plant buds and barks, and subsequent mixing with the salivary enzyme β-glucosidase. Bees use propolis in their combs as protection, to repair damage, to build aseptic locals for the eggs of the queen, and also as a thermal insulator. The composition of propolis varies geographically, with the available flora, the time of collection and the race of the bees. Different groups of compounds can be found in propolis such as polyphenols, terpenoids, steroids and amino acids. Some of these compounds have been associated with diverse biological activities: antimicrobial, antioxidant, antigenotoxic, genotoxic and antimutagenic. Portuguese propolis has recently attracted the interest of researchers because of the opportunity for its economic valorization and the need to scientifically support the biological properties commonly assigned to samples of different origins. Thus, our objective relates to the analysis and study of Portuguese propolis, particularly in what concerns its chemical characterization and the evaluation of biological activities. A propolis ethanol extract (PEE) was made from a sample provided from an apiary (Côa) in Beira Alta and tested in different assays, using Saccharomyces cerevisiae as biological model. We have performed viability assays in pre-, co- and post-incubation conditions using PEE and 5mM hydrogen peroxide (H2O2) in order to investigate the effect of PEE as antioxidant and/or protective agent against oxidative stress. The comet assay was used in pre- and co-incubation to complement the previous method and to investigate the antigenotoxicity/genotoxicity of PEE under the same conditions. Chemical analysis of the extract was made to determine total polyphenol and flavonoid contents as well as antioxidant capacity of propolis. Results show that Portuguese propolis has antioxidant capacity when assessed by DPPH and ABTS assays. Accordingly, the viability of yeast cells shocked with the oxidant agent H2O2 was improved in the presence of propolis, either in pre-incubation or in co-incubation conditions. However, when cells were analyzed by the comet assay, the antigenotoxicity of PEE was more evident in pre-incubation than in co-incubation assays. In addition, our results suggest that propolis has also a genotoxic effect in yeast cells, since cells treated only with PEE displayed more DNA damage that the untreated ones.